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Wireless Sensor Networks for Monitoring Cracks in Structures

1. 0 25 jj 12 AMBIENT TEMPERATURE Popular Resistance Values 101 102 Circuits BOUR Dual Terminator 104 Circuit Model 4600X 104 R1 R2 4 through 14 Pin 8 The 4608X 104 shown above is an 8 pin configuration and terminates 6 lines Pins 1 and 8 are common for ground and power respectively Twelve thick film resistors are paired in series between the common lines pins 1 and 8 Resistance Tolerance Below 100 ohms 100 ohms to 5 megohms 2 ohms x2 96 Above 5 megohms 2 5 Power Rating per Resistor DAL TOG 0 20 watt Power Temperature Derating Curve 50 40 30 WATTS 20 10 0 25 76 125 AMBIENT TEMPERATURE C Ohms Code Ohms Code Ohms Code Ohms Code Ohms Code Popular Resistance Values 104 Circuit 10 100 180 181 1 800 182 15 000 153 120 000 124 22 220 220 221 2 000 202 18 000 183 150 000 154 Resistance 27 270 270 271 2 200 222 20 000 203 180 000 184 Ohms Code 33 330 330 331 2 700 272 22 000 223 220 000 224 39 390 390 391 3 300 332 27 000 273 270 000 274 Ry R2 Ry R2 47 470 470 471 3 900 392 33 000 333 330 000 334 160 240 161 241 56 560 560 561 4 700 472 39 000 393 390 000 394 180 390 181
2. Logging 4 2 25 8 12 Bit A D s Em MUX 51 Pin Expansion Connector MDA300C Block Diagram Phone 408 965 3300 Fax 408 324 4840 137 Crossb w MDA300 Developed at UCLA s Center for Embedded Network Sensing CENS the MDA300 is an extremely versatile data acquisition board that also in cludes an onboard temperature humidity sensor With its multi function direct user interface the MDA300 of fers a convenient and flexible solution to those sensor modalities commonly found in areas such as environmental and habitat monitoring as well as many other custom sensing applications As part of a standard mesh network of Motes the MDA300 easy access micro terminals also make it an economical solution for a variety of ap plications and a key component in the next generation of low cost wireless weather stations Data logging and display is supported via Crossbow s MoteView user interface Crossbow s MoteView software is designed to be the primary interface between a user and a deployed net work of wireless sensors MoteView provides an intuitive user interface to database management along with sensor data visualization and analysis tools Sensor data can be logged to a database residing on a host PC or to a database running autonomously on a Stargate gateway
3. Bay aop 1eyeuoquajod SSM 90 ost BAY AON LOA1 1 E lc t AON 1 SSAIM os wn ost 5002 002 8 44 From November 2004 through January 2005 the system took data once per hour Because of the provision of the communication window for the issuance of new commands each mote was fully powered on and awaiting instructions for a full five minutes out of every hour a duty cycle of just over 8 It is no surprise then that the system consumed all of its available battery power in only one month the batteries were changed in late December of 2004 Figure 3 9 shows the decline of the alkaline AA battery voltage over the time of deployment until it was no longer sufficient to support logging and data collection halted More detailed analysis of power consumption can be found in Ozer 2005 3400 3200 27 days of field operation 4 8 5 2 3000 a 2800 T T T T 12 19 05 12 29 05 1 8 06 1 18 06 1 28 06 Time Figure 3 9 Alkaline battery voltage decline of a mote running MDA300Logger after Ozer 2005 3 3 4 5 Results
4. Potentiometer Specifications Potentiometer Type 1 turn precision conductive plastic Resistance Value Tolerance 5K ohms 10 Travel Electrical Mechanical 340 340 min Mechanical Life 5 million shaft revolutions min Output Signal lanalog signal from 0 to supply voltage voltage divider circuit Power Rating 0 75 W at 158 F 70 C Supply Current 12 mA max Supply Voltage 35 VDC max using voltage divider circuit Independent Linearity Error 1 0 max per VRCI P 100A Output Smoothness 0 196 max Insulation Resistance 1000 Mohms at 500 VDC min Dielectric Strength 500 VDC min Resolution infinite signal Operating Temperature 85 to 257 F 65 to 125 C Shock Vibration 100 g for 6 ms 10 to 2000 Hz at 15 g per Mil R 39023 Temperature Coefficient 400 max Other Specifications 1 of 3 Data Sheet Series 150 Subminiature Position Transducer 2 of 3 http www firstmarkcontrols cony s021f htm Case Materials lprecision machined anodized 2024 aluminum Displacement Cable 0 018 inch 0 46 mm dia 7 by 7 stranded stainless steel 40 Ib 177 N breaking strength Displacement 1 each of 300196 loop sleeve 300292 copper sleeve 300688 ball end plug 300495 pull ring 160026 brass swivel and 301003 nickel swivel all items Cable Hardware provide
5. 5 5 E H i x amp 1 100 4 200 1 13 14 15 16 17 1 19 20 21 Time seconds Figure A 4 Shake n Wake Level 2 trigger threshold test results for HS 1 geophone at 5 hertz For each of the set of test frequencies averages of the voltage level at which the Shake n Wake triggered were computed Figure A 6 graphically summarizes these results Based on the anal ysis of the idealized trigger threshold reference circuit in Figure 3 24 the theoretical value at which the Shake n Wake should trigger regardless of the sensor to which it is attached is 7 116 millivolts Figure A 6 indicates that the Shake n Wake is actually triggered at a higher 122 05 13 Geophone Triggers at S n W Level 2 100 T T Input Waveform Shake n Wake Triggers geophone output mV e Time seconds Figure A 5 Shake n Wake Level 2 trigger threshold test results for GS 14 geophone at 5 hertz voltage threshold than predicted and the actual trigger threshold varies with frequency of the output of the geophone These results indicate that the idealized analysis is not adequate to determine the actual volt age threshold at which the Shake Wake will trigger frequency also must be taken into account when determining this voltage The dependence of the Shake n Wake s comparators on the fre quency of their input voltage can be
6. Description Communication and Control Features Including 7 single ended or 3 differential ADC channels 4 precise differential ADC channels digital I O channels with event detection interrupt 2 5 3 3 5V sensor excitation and low power mode 64K EEPROM for onboard sensor Calibration data e 2 relay channels one normally open and one normally closed 200 Hz counter channel for wind speed pulse frequencies External I2C interface Drivers for the MDA300 board are included in Crossbow s MoteWorks software platform MoteWorks enables the development of custom sensor applications and is specifically optimized for low power battery operated networks MoteWorks is based on the open source TinyOS operating system and provides reliable ad hoc mesh networking over the air programming capabilities cross development tools server middleware for enterprise network integration and client user interface for analysis and configuration Ordering Information Mote Data Acquistion Board with Temperature and Humidity fo xbow com Document Part Number 6020 0052 03 Rev A Web www xbow com 510 Data Sheet MIB510 SERIAL INTERFACE BOARD Base Station for Wireless Sensor Networks Serial Port Programming for IRIS MICAz and MICA2 Hardware Platforms Supports JTAG code debugging Applications Programming Interface e RS 232 Serial G
7. Appearance _ 1 Appearance 8 ch Digital Input UC 7408 Reset to Default Dl Reset to 12345678 Defaut Reset P6 B Serial Port x 8 RJ45 RS 232 422 485 Hardware Reset UC 7420 7410 7408 www moxa com infoGmoxa com 151 152 gt gt Embedded Computers 12 48 VDC PCMCIA x 1 Power Input UC 7420 7408 7402 USB 2 0 Host x 2 A Type Connector UC 7420 LAN2 Console ____ ____ LL USB 1 1 Client x1 miniB Connector RS 232 10 100 Mbps Console Port Ethernet x 2 DC 12 48V PCMCIA Rear View Vt V h CFx1 UC 7420 7408 7402 Hardware Specifications Computer CPU UC 7410 7420 Intel XScale IXP422 266 MHz UC 7410 7420 Plus Intel XScale IXP425 533 MHz OS pre installed Embedded Linux or Windows CE 5 0 DRAM 128 MB onboard Flash 32 MB onboard PCMCIA Cardbus card and 16 bit PCMCIA 2 1 ro JEIDA 4 2 card UC 7420 only USB USB 2 0 compliant hosts x 2 A type connector USB 1 1 client x 1 mini B connector Storage Storage Expansion CompactFlash socket UC 7420 UC 7420 Plus Ethernet Interface LAN 2 auto sensing 10 100 Mbps ports RJ45 Magnetic Isolation Protection 1 5 KV built in Serial Interface Serial Standards RS 232 422 485 software selectable 8 pin RJ45 8 ports ESD Protection 15 KV for all signals Console Port RS 232 all signals RJ45 connector supports PPP Serial Communication P
8. E 4 1 x x X 4 E e Vf 8 OF PH 4 5 Fer a A E Ap WE 5 5 1000 4 E H El s 5 2000 5 4 4 Bees 4 C 8 3000 I 4 or 4000 L 5000 1 some xL ae same ae 1 1 1 1 1 80 90 100 120 130 140 150 80 90 100 110 120 130 140 150 Days Deployed Days Deployed Figure 3 32 Plots of a temperature b humidity c crack displacement and d Shake n Wake triggers recorded by the Version 3 of the wireless ACM system over the 75 day period of interest 3 3 7 6 Discussion Figure 3 31c shows the alkaline battery voltage versus deployment time for Version 3 of the MICA2 based ACM system Figure 3 33 compares the battery voltage versus time of Ver sions 2 and 3 of the two MICA2 based wireless ACM systems The two Version 3 motes with boards installed lasted approximately 150 days The graph indicates however that battery voltage decay curve of the more economical batteries used in Version 3 did not 77 match those used in Version 2 This evidence added to the similar current consumption files shown in Figure 3 11 indicates that Version 3 can operated for at least six months when high quality alkaline batteries are used Battery vs Days Deployed Mote 3 Version 3 Mote 4 Version 3 4 Mote 1 Version 2 Mot
9. Figure 3 28 Current draw of a wireless ACM Version 2 mote with no Shake n Wake after Dowding et al 2007 b Version 3 mote with Shake n Wake 72 3 3 7 4 Deployment in Test Structure A deployment test of Version 3 of the MICA2 based wireless ACM system was conducted in the main building of the test structures near the Northwestern campus described in Section 3 3 5 4 between September 2007 and February 2008 The objective of the test was to determine the degree of difficulty of the installation of the system the effectiveness of the Shake n Wake in detecting vibration events and further assurance that Shake n Wake does not significantly decrease deployment lifetime of the system Sensor nodes were deployed through only one of the structures as shown in Figure 3 29 Two geophone only nodes with no MDA300CA or string potentiometer were installed on the underside the service stairway leading from the basement to the kitchen as pictured in Fig ure 3 30a One of these motes was connected to a GS 1 geophone the other was connected to an HS 1 geophone Two motes each equipped with a MDA300CA sensor board a Shake n Wake sensor board an HS 1 geophone in a mounting bracket and a string potentiometer were in stalled over existing cracks in the structure one over the doorway leading from the kitchen into the service stairway to the second floor shown in Figure 3 30b and one on the wall of the main stairway leading from the second
10. Kotowsky M P Dowding C H and Fuller J K 2009 Poster summary Wireless sensor networks to monitor crack growth on bridges In Proceedings Developing a Research Agenda for Transportation Infrastructure Preservation and Renewal Conference Washington DC Transportation Research Board Louis M 2000 Autonomous Crack Comparometer Phase II Master s thesis Northwestern University Evanston Illinois Macro Sensors 2009 Macro sensors DC 750 series general purpose DC LVDT position sensors http www macrosensors com lvdt macro sensors lvdt products lvdt position sensors dc lvdt free core dc dc 750 general purpose html Marron D R 2010 Personal communication with Chief Research Engineer at the Infrastruc ture Technology Institute at Northwestern University Maxim Integrated Products 2003 SOT23 Dual Precision 1 8V Nanopower Comparators With Without Reference Part number MAX9020EKA T Maxim Integrated Products Inc 2009 1024 bit 1 wire eeprom data sheet McKenna L M 2002 Comparison of measured crack response in diverse structures to dy namic events and weather phenomena Master s thesis Northwestern University Evanston Illinois Moxa Inc 2010 UC 7410 7420 Series http www moxa com doc specs UC 7410 7420 Series pdf Ozer H 2005 Wireless sensor networks for crack displacement measurement Master s thesis Northwestern University Evanston Illinois Puccio M 2010
11. Two types of phenomena exist that tend to cause changes in crack width and therefore possible elongation or growth of crack The first type so called long term effects are those that must be measured over the periods of hours days months and years in order to realize their effect on crack behavior The other type so called dynamic effects are the motions in cracks induced by vibration blasting slamming of doors leaning against walls and other common household activities These phenomena tend to be short lived i e fewer than fifteen seconds in duration and must be observed at a high frequency to realize their true effect on cracks Additionally these dynamic phenomena cannot be expected to occur on a predictable schedule therefore an ACM system must be constantly aware of its sensor inputs to determine whether such an event is occurring wired ACM system is able to measure both long term and dynamic events 2 4 1 1 ACM Mode 1 Long term Effects that can be observed using only hourly measurements include changes in temperature and humidity as driven by weather or the utilization of in home heating and cooling systems or kitchen appliances such as ovens and stoves Measuring these effects more frequently than a few times per hour will yield no new information about the cracks as temperature and humidity changes are slow produce changes in crack width To capture accurately these phenomena and their effects on cracks ev
12. output of the Shake n Wake to which it is attached and the output of a GS 14 geophone is 120 S n W vs Control HS 1 2000 T T T T T T T Control geophone Geophone attached to S nW 1500 1 1000 4 500 4 Input singal mV 500 4 1000 1 46 46 5 47 47 5 48 48 5 49 49 5 50 Time seconds Figure 2 Shake n Wake transparency test results for HS 1 geophone recorded on the same time scale as the output of the Shake 7 Wake to which it is attached Both geophones were placed on a cantilevered aluminum springboard with identical distances from the fulcrum Figure A 3 shows this experimental setup The length of the springboard was decreased successively to produce response frequencies of 5 10 15 and 20 hertz thereby spanning the frequency range of interest for structural motion in response to a vibration event The Shake n Wake was set to level 2 of 31 the most sensitive level that could be used while avoiding false triggers from ambient vibration of the springboard Figures A 4 and A 5 show the voltage level at which each Shake n Wake triggers with a threshold setting of level 2 when the geophones are moved at a frequency of 5 hertz 121 Figure A 3 Shake n Wake trigger threshold test apparatus HS 1 Geoghome Triggers at 5 W Level 2 200 T Input Waveform Shake Wake Triggers 100 00 1 i n i 1 8 IT
13. WEIGHT DIAMETER HEIGHT Less Stud STUD LENGTH PARTNUMBER 98449 SPECIFICATION 25 C HORIZONTAL 4 5 Hz 259 SHz 3 25 5 75 Hz gt 140 Hz TYPICAL 1200 1 04 V in sec 0295 JR 4 45 to 100 C 100 C continuous duty 8 75 oz 248 g 1 625 in 4 128 2 00 in 5 08 310 787 GEO SPACE CORPORATION 150 CH 001 08 gg 07 gc gr et at 8 e 9 L 01 4 5 a WSILIED 30 X go LINDYID Iii LI O3S NI N yg ALIAILISN3S DISNINLNI 2 52 LY 5 goz 32NV1SIS3M 2 0 F TH G y _ TIYYNLYN 1 T7 02 72808 300W 1 GH SAL SA 1 41 0 ASNOdS3SY 0123130 JIWSIAS ge V s n svxai NOLSNOH eum __ tA Af T cH MY is 3 Lung 2 11 ud ia M E LI _ _ y lt 097 22122141 KAT SWHO gZer xez N3dO bac orano ive NE MINE ns 5235 0 LNA LNG B 10 UC 7420 Data Sheet gt gt Embedded Computers UC 7410 7420 Series RISC ready to run computers with 8 serial ports dual LANs USB PCMCIA CompactFlash web server Windows Embedded gt 128 MB RAM onboard 32 MB flash gt 8 RS 232 422 485 serial ports gt
14. 20 45 t2 t 58 0 Us 1 t2 31 0 us E ee RS t t Geophone 50mV div IRQ 4 V div LED 4 V div Current 5 mA div Figure 9 Scope readout indicating the mote can execute user code within 89 us of a signal of interest after Jevtic et al 2007b A 4 1 Upper Frequency Limit Shake n Wake Response Time A mote attached to a Shake n Wake will be executing user code 89 us after a geophone voltage of interest Using the same assumption that the mote must be awake for at least one full sample period before the peak of interest and that it will be sampling at 1000 hertz once it wakes up the minimum time between the wakeup signal and the arrival of the peak of the event is 1 089 milliseconds Figure A 8 indicates that the rise time of an idealized sinusoidal input signal is 25 of its period If the rise time must be at least 1 031 milliseconds then the period must be at lest 4 356 milliseconds and the frequency must be at most 230 hertz Thus in order for a node to be executing user code in time to catch the first peak of a dynamic event of interest the maximum frequency of the event is 230 hertz 129 A 4 2 Lower Frequency Limit Geophone Output Amplitude The GS 14 and HS 1 geophones output amplitude for a given input velocity varies with fre quency as shown in the response spectra in Appendices B 8 and B 9 respectively Figure A 7 shows that for the GS 14 geophone the frequency of motion must be
15. 5 CAMERA 0 8 20 40 60 80 100 120 Service minutes Important Notice This data sheet contains typical information specific to products manufactured at the time of its publication GEnergizer Holdings Inc Contents herein do not constitute a warranty Form No EBC 1102L Page 2 of 2 143 B 7 Lithium Battery Data Sheet PRODUCT DATASHEET Energizer 1 800 383 7323 US CAN WWW energizer com ENERGIZER L91 Specifications Ultimate Lithium Classification Cylindrical Lithium 2 Chemical System Lithium Iron Disulfide Li FeS Lfnergizer Designation ANSI 15 LF IEC FR6 Nominal Voltage 1 5 Volts SED Storage Temp 40 C to 60 C 40 F to 140 F Operating Temp 40 C to 60 C 40 F to 140 F gt Typical Weight 14 5 grams 0 5 oz Industry Standard Dimensions Typical Volume 8 0 cubic centimeters 0 5 cubic inch mm inches Max Discharge 2 0 Amps Continuous single battery only 3 0 Amps Pulse 2 sec on 8 sec off Max Rev Current 20 Typical Li Content 0 98 grams 0 03 oz Typical IR 90 to 150 milliohms 14 50 0 571 Shelf Life 15 years at 21 C 90 of rated capacity 13 50 0531 Transportation For complete details please reference a 0 039 Global except US Special Provision 45 of the International i Mn Air Transport Association Dangerous Li Minimum Goods Regulations GO United States 49 CFR 173 185 For additional information please reference
16. Contents herein do not constitute a warranty Form No EBC 1102L Page 1 of 2 PRODUCT DATASHEET ENERGIZER E91 Constant Power Performance Typical Characteristics 21 C 100 3 8 10 8 4 9 1000 Discharge mW Constant Power Performance Discharge Characteristics 21 C Energizer 1 800 383 7323 USA CAN WWwW energizer com Constant Current Performance Typical Characteristics 219C 1000 100 8 10 0 8 Volts H 1 0 Volts 1 2 Volts 1 10 1000 Discharge mA Constant Current Performance 250 mA Discharge 20 C 0 C 21 C 1 6 15 14 81 2 1 2 511 510 0 9 0 8 8 16 24 32 0 2 4 6 8 Service hours Service hours Industry Standard Tests 21 C REMOTE RADIO PORTABLE LIGHTING TOY 24 ohm 15 sec min 8 hrs day 43 ohm 4 hrs day 3 3 ohm LIF 3 9 ohm 1 hr day _ 16 _ 16 gt gt 8 14 RADIO 8 14 H 1 2 1 2 TOY 51 0 REMOTE 5 1 0 LIGHT gt gt 0 8 0 8 0 20 40 60 80 100 0 2 4 6 8 10 Service hours Service hours CD GAMES TAPE PLAYER DIGITAL CAMERA PHOTOFLASH 250 mA 1 hr day 100 mA 1 hr day TAPE PLAYER CD GAMES Voltage CCV oF mem DD N 0 7 14 21 28 Service hours 1 5K 65K mW 2 28 sec 10x hr 1K mA 10 sec min 1 hr day 1 6 E 8 14 1 2 PHOTO 510
17. Listening and or transmission Sleeping 0 042 mA Figure 3 11 Current draw profile of mote running the modified XMDA300 software for Mode 1 recording the periodic sampling window is shown in the dashed oval in the inserted figure demonstrating intermittent operation compared to ongoing operation after Dowding et al 2007 Sensor nodes were deployed throughout two structures as shown in Figure 3 12 In the main building shown on the right the Stargate base station was installed in the first floor office such that it could be connected to the building s high speed Internet connection Additional sensor nodes were placed on each floor of the main structure one in the basement Figure 3 13a one on a sun porch on the second floor Figure 3 13b and one near a window in the third floor apartment Figure 3 13c To increase the likelihood that the XMesh routing protocol would form a multi hop network a node was placed on the second floor of the structure s detached garage Figure 3 13d some sixty feet away from the main building Neither the sun porch nor the garage had any insulation or climate control systems to keep their temperatures from being affected by the outdoor temperature 51 Figure 3 12 Distribution of sensor nodes throughout test structures Because qualification of the string potentiometer had already been completed during the deployment of Version 1 in parallel with a wired ACM system
18. Version 1 of the MICA2 based wireless ACM system was largely successful It showed that the MICA2 combined with the MDA300CA and a string potentiometer could perform Mode 1 data 45 recording on par with a state of the art wired ACM system In spite of these positive results however several improvements would still be necessary to achieve a fully functional Mode 1 system before a Mode 2 system could be developed e Power management must be improved the minimum target deployment life of a wire less ACM system is six months but the MDA300Logger system lasted only one e Data retrieval is difficult a user of MDA300Logger must remember when data was last uploaded to know when the next window will be available Should the motes clocks drift the window might become difficult to find e The MDA300Logger system has no ability to route data through other motes In com plex or RF noisy residential environments or in structures where the base station may not be within radio range of all of the motes multi hop routing will be necessary 46 3 3 5 MICA2 Based Wireless ACM Version 2 XMesh Based on the newly released XMesh enabled example applications developed by the WSN man ufacturer Version 2 made use of largely the same hardware but an entirely different software design to better implement Mode 1 logging The design goal of Version 2 was to create wireless ACM system that e increased system operation lifetime from one month to at
19. b wide gage affixed with elevated temperature cured adhesive Coupon C was subjected to the same testing procedure as were Coupons A and B but the testing was aborted when it was observed that the room temperature cured adhesive had failed before the gage itself as shown in Figure 4 14 Figure 4 14 Photograph of glue failure on wide gage affixed with room temperature cured adhesive the indicated region shows the glue failed before the gage 97 4 2 3 Results and Discussion Coupons A and B 0 35 T T T T T T T T T Narrow Coupon A Wide Coupon 025 4 0 15 Sensor Reading 0 1 1 1 1 1 1 1 1 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Elapsed Seconds Figure 4 15 Data recorded by eKo mote during tests of Coupons A and B Figure 4 15 shows the data recorded by an eKo mote during tests of Coupons A and B The wide gage showed a linear change of voltage versus number of broken rungs Eight rung breaks are easily identifiable The narrow gage showed a non linear change of voltage versus number of broken rungs Figure 4 13a clearly indicates that all twenty rungs have been broken by the crack but Figure 4 15 only shows ten discernible increases in voltage This result is not unexpected the 10 bit analog to digital conversion unit and the 3 V DC precision excitation voltage on the mote combine to limit the minimum viewable change in voltage output
20. dynamic even recording as discussed in section 2 4 1 2 2 2 Crack Width Siebert 2000 describes the high resolution with which the change in width of a typical household crack must be measured 0 1 4 to capture fully even its smallest changes This plays a significant role in the selection of the transducer to measure the crack It is shown in Chapter 3 the resolution requirements have a different impact on a wireless ACM system than on a traditional wired ACM system Only the change in crack width is significant as shown in Figure 2 2 Instruments Field Computer Datalogger Internet connection ortelephone modem a Site Researchers Practitioners Polling Computer Internet enabled O databaseserver Other Stakeholders Users Figure 2 1 Flow of data from sensors to users after Kosnik 2007 TYPICAL CRACK CHANGE IN CRACK WIDTH TOTAL CRACK WIDTH ORIGINAL CRACK WIDTH Figure 2 2 Sketch of a view of a crack to illustrate the difference between crack width and crack displacement change in crack width redrawn after Siebert 2000 2 3 A Wired ACM System The basic ACM system measures four different physical quantities particle velocity of the ground on which the instrumented structure rests changes in widths of cracks within the struc ture ambient temperature both inside and outside the structure and ambient relative humidity both inside and
21. movement from a string potentiometer this assumes an environment free of all electromagnetic interference and ambient vibration 38 3 3 3 Software and Power Management The MICA2 and MDA300CA and MIB510CA compose the hardware of the wireless sensor network Specialized software runs on each individual MICA2 mote to control sensing manage transmission of data maintain the connectivity of the mesh network if necessary and regulate power consumption to maximize system longevity When software alone cannot meet all system design specifications hardware solutions can be employed as in Section 3 3 6 to make the wireless ACM system more useful 3 3 4 MICA2 Based Wireless ACM Version 1 The first iteration of the wireless ACM system had a modest design goal Implement Mode 1 data recording while maximizing system longevity Version 1 did not attempt to implement multi hop mesh networking or sophisticated power management It was deployed in a occu pied single family home near an active limestone quarry A traditional wired ACM system was already installed in the home and the deployment location an already monitored crack in the ceiling was chosen to corroborate the wireless sensor readings with those taken with the established wired system 3 3 4 1 Hardware Version consisted of two MICA2 motes each equipped with an MDA300CA sensor board and a single string potentiometer An aluminum plate was attached with screws to the bottom o
22. structure Four laboratory experiments of ACPS systems and sensors are presented the first three show the functionality of commercially available crack propagation sensors and a WSN sys tem adapted from the agricultural industry The final experiment shows the functionality of a newly invented form of crack propagation gage that allows for a more flexible installation of the sensor iii Acknowledgements This thesis represents the climax of a serendipitous chapter in my career in which I found an unexpected outlet in civil engineering for my interest and skills in computers and electronics Many teachers co workers family and friends have been a part of this process and to them I give my most sincere thanks First I would like to thank my M S thesis committee Professor Charles H Dowding and Professor David J Corr for their guidance and direction during my entire graduate school ex perience Entering the field of civil engineering with an undergraduate background in computer engineering was a challenge through which these two gentlemen saw me with advice on every thing from course selection to conference attendance and everything in between While I was a sophomore in computer engineering at the University of Illinois at Urbana Champaign Professor Dowding hired me as an undergraduate programmer to assist over the In ternet and on school breaks in his Autonomous Crack Monitoring project sponsored by North western University s In
23. 391 68 680 680 681 5 600 562 47 000 473 470 000 474 220 270 221 271 82 820 820 821 6 800 682 56 000 563 560 000 564 220 330 221 331 400 101 1 000 102 8 200 822 68 000 683 680 000 684 330 390 331 391 120 121 1200 122 10 000 103 82 000 823 820000 824 330 470 331 271 150 151 1 500 152 12 000 123 100 000 104 1 000000 105 3 000 6 200 302 622 1 TOLERANCE IS AVAILABLE BY ADDING SUFFIX CODE F AFTER THE RESISTANCE CODE NON STANDARD VALUES AVAILABLE WITHIN RESISTANCE RANGE REV 12 06 Specifications are subject to change without notice Customers should verify actual device performance in their specific applications 155 156 B 12 Conductive Data Sheet CHEMTRONICS Technical Data Sheet CircuitWorks Conductive Pen PRODUCT DESCRIPTION TYPICAL PRODUCT DATA AND PHYSICAL PROPERTIES CircuitWorks Conductive Pen makes instant highly conductive silver traces on Composition circuit boards CW2200 is used in Material Silver Filled Polymer prototype rework and repair of circuit Silver Particle Size 10 15 microns boards by linking components repairing Color Silver Gray defective traces and making smooth Setting Rate lt 2mm hr jumpers The silver traces dry in minutes Properties and have excellent adhesion to most Conductivity 0 02 0 05 ohms sq mil electronic materials Engineers repair 0 00005 0 000125 ohm cm tech
24. 46 06 X 101 222 _ LF Model 4 46 Conformal SIP Number of Pins Physical Configuration X Thick Film Low Profile Electrical Configuration 101 Bussed 102 Isolated 104 Dual Terminator Bussed Ammo AP2 Isolated Ammo Dual Ammo Resistance Code e First 2 digits are significant Third digit represents the number of zeros to follow Resistance Tolerance Blank 2 96 see Resistance Tolerance on next page for resistance range F 1 96 100 ohms 5 megohms Terminations All electrical configurations EXCEPT 104 amp LF Sn Ag Cu plated RoHS compliant ONLY electrical configurations 104 amp AP4 L Sr Ag Cu plated RoHS compliant Consult factory for other available options Available for packages with 10 pins or less Features m RoHS compliant m Low profile is compatible with DIPs m Wide assortment of pin packages enhances design flexibility m Ammo pak packaging available m Recommended for rosin flux and solvent Clean or no clean flux processes Package Power Temp Derating Curve m Marking on contrasting background for permanent identification 4600X Series Thick Film Conformal SIPs Product Dimensions 5 08 maximum
25. 52 and 30 resis tance respectively which will increase as their rungs are broken acting as open circuits when all rungs have been broken Because the crack propagation patterns are purely resistive sensors and the eKo mote is only able to record voltages two precision resistors were used to create a circuit to convert the resistance output into a voltage The 49 90 resistor was placed in parallel with the two terminals of the crack propagation pattern while the 3740 a resistor was placed in series with the mote itself Figure 4 9 shows a schematic of this circuit 92 Crack Propagation Gage GND Sig Figure 4 9 Diagram of sensor readout circuit adapted from Vishay Intertechnology Inc 2008 This circuit can be connected to either the narrow or wide gage and will cause each rung break of a wide pattern to register an increase of approximately 10 millivolts on the eKo mote Because the resistance change is so small the first rung breaks of a narrow sensor will register no measurable voltage difference on the eKo mote but the last several rungs broken will register a significantly higher voltage change than the rungs of a wide gage The circuit was placed within the custom cable so that two exposed leads at the opposite end of the cable from the watertight connector may be soldered to the two terminals of the crack propagation pattern after it has been mounted on the target material In addition to the fabrication of the custom
26. 72 E Mote 1 854 9 854 9 853 9 2561 7 Mote 2 37 z 096 102 1 81 1 220 1 Mote 3 5440 61 4 50 309 3 5753 15 Mote 4 1977 22 0 0 1977 5 Total 8973 9441 9437 9417 37 268 Table 3 1 Distribution of MICA2 based wireless ACM Version 2 packets over the parents to which they were sent Parent vs Days Deployed Parent ID r Mote 1 2 3 Mote 4 UE Sei 150 Days Deployed 300 Figure 3 20 Plot of each Version 2 wireless ACM mote s parent versus time 59 Figure 3 16 shows that Mote 2 the mote in the basement directly underneath the room with the base station depleted its battery more quickly than any other mote Although Mote 2 is physically closer to the base station than any of the other motes Table 3 1 reveals that only 1 of packets from other motes were transmitted first through Mote 2 on their way to the base station Figure 3 20 also shows that Mote 2 did not act as a parent mote for longer than Mote 3 did Because only 28 of the total ACM packets transmitted went through an intermediary mote on their way to the base station and because Mote 3 after having been a parent mote for 15 times more packet transmissions as Mote 2 did not deplete its batteries it is unlikely that overuse as an intermediary mote caused Mote 3 to drain it
27. Because the UC 7420 was not designed to connect to a mote via the mote s 51 pin connector an MIB510CA serial interface 66 Figure 3 25 Photograph of Version 3 wireless ACM node board was used to connect the base mote to one of the serial ports on the UC 7420 Detailed specifications of the UC 7420 can be found in Appendix B 10 Second instead of relying on a locally available Internet connection to connect back to the laboratory the Version 3 base station includes a 3G cellular router and antenna The inclusion of the cellular router allows placement of the base station at any location in an instrumented structure as long as that location has available cellular signal and 110 V AC power Figure 3 26 shows a photograph of the base station Physical installation of Version 3 of the MICA2 based wireless ACM system is an extension of Versions 1 and 2 the MICA2 MDA300CA string potentiometer combination is mounted to the wall in the same manner as in Version 1 The geophone as it needs to be coupled closely with the wall or ceiling to be monitored requires rigid attachment to the wall using epoxy but the mote and sensor boards may be fastened to the wall only hook and loop fasteners The HS 1 67 Figure 3 26 Photograph of the base station of Version 3 of the wireless ACM system including UC 7420 MIB510CA cellular router power distributor and industrially rated housing geophone features a threaded protrusion for ease of ins
28. Dual 10 100 Mbps LANs for network redundancy gt USB2 0 host gt CompactFlash socket for storage expansion gt PCMCIA supporting WLAN GPRS UMTS HSDPA gt LCM display and keypad for HMI gt Built in firewall and VPN function gt Apache web server supporting PHP and XML Ready to run Linux or WinCE 5 0 platform DIN rail or wallmount installation Robust fanless design Gc3llccre Overview The UC 7410 7420 Series RISC based ready to run Linux and WinCE computers are designed for embedded applications The computers feature 8 RS 232 422 485 serial ports a POMCIA interface for wireless LAN communication CompactFlash and USB ports for adding external memory The built in firewall VPN and web server make these computers ideal for applications that require a web server and front end controller in the industrial embedded system 8 ch Digital Output UC 7408 DO Front View 123456785 RS 232 422 485 The pre installed open standard Linux or WinCE OS operating system provide a convenient platform for software development In fact software written for a desktop PC can be ported as is to the UC 7410 7420 platform using readily available development tools and the code can be stored in the UC 7410 7420 s Flash memory System integrators will find it easy to use the UC 7410 7420 computers as part of distributed control systems based on embedded technology
29. Personal communication with Application Engineer of Macro Sensors 116 Siebert D 2000 Autonomous Crack Comparometer Master s thesis Northwestern Univer sity Evanston Illinois Snider M 2003 Crack response to weather effects blasting and construction vibrations Master s thesis Northwestern University Evanston Illinois SOLA HD 2009 SCL Series 4 and 10 Watt CE Linears http www solahd com products powersupplies pdfs SCL pdf SoMat Inc 2010 eDAQ Simultaneous High Level Layer http www somat com products edaq edaq simultaneous high level layer htmlf tabs 1 2 Speckman G M 2010 Personal communication with Regional Sales Manager of Kaman Sensors Stolze F J Staszewski W Manson G and Worden K 2009 Fatigue crack detection in a multi riveted strap joint aluminium panel In Kundu T editor Health monitoring of structural and biological systems volume 7925 Bellingham Wash SPIE Switchcraft Inc 2004 EN3 Cord Connector The Sherwin Williams Company 2019 MACROPOXY 646 FAST CURE EPOXY United States Department of Transportation Federal Highway Administration 2006 Bridge Inspector s Reference Manual volume 2 National Highway Institute Vishay Intertechnology Inc 2008 Special use sensors crack propagation sensors Waldron M 2006 Residential crack response to vibrations from underground mining Mas ter s thesis Northwestern University Evanston Illino
30. Technology Inc 2009b pro series users manual http www xbow com eko pdf eKo Pro Series Users Manual pdf Crossbow Technology Inc 2009c ESB developer s guide Crossbow Technology Inc 2009d MIB 510 Serial Interface Board http www xbow com Products Product_pdf_files Wireless_pdf MIB510CA Datasheet pdf 114 Crossbow Technology Inc 2009 MICA2 Wireless Measurement System http www xbow com Products Product_pdf_files Wireless_pdf MICA2_Datasheet pdf Dowding C H 1996 Construction Vibrations Prentice Hall Upper Saddle River New Jersey Dowding C H Kotowsky M P and Ozer H 2007 Multi hop wireless system crack measurement for control of blasting vibrations In Proc 7th Int l Symposium on Field Mea surements in Geomechanics Boston Massachusetts American Society of Civil Engineers Energizer Holdings I 2010a Product datasheet Energizer e91 http data energizer com PDFs E91 pdf Energizer Holdings I 20106 Product datasheet Energizer 191 http data energizer com PDFs 191 pdf Firstmark Controls 2010 Data sheet series 150 subminiature position transducer http www firstmarkcontrols com s021f htm for Testing A S and Materials 2006 Standard Test Method for Determination of Resistance to Stable Crack Extension under Low Constraint Conditions ASTM E2472 Geo Space Corporation 1980 GEO GS 14 L3 28 HZ 570 OHM Part number 4106
31. and 2 5 kip at 10 hertz was applied to the specimen until failure 4 3 4 Results and Discussion After approximately one hour of fatigue testing the crack propagated through the entirety of the region covered by the custom crack gage Figure 4 21 shows that all four painted rungs are cleanly broken Figure 4 22a shows a plot of the gage output versus time Because this data was taken with a wired data logger it is more susceptible to the electromagnetic interference generated by the test apparatus Figure 4 22b shows the results of the application of a 0 1 hertz low pass Butterworth filter to the data The data clearly show four distinct rung breaks Figure 4 21 Coupon with custom gage after all rungs broken 106 Figure 4 22 Custom crack gage output versus time a unfiltered Custom Crack Gage Output Unfiltered 3 T T T T T T 28 E 2 6 j S E T 8 4 5 5 n 1 1 1 1 1 1 0 500 1000 1500 2000 2500 3000 3500 Elapsed Seconds a Custom Crack Gage Output Low Pass Filtered 3 T T T T T T 28 2 6 al e 24 4 E 2 55L 1 3 2 2 1 4 1 6 4 1 1 1 1 1 1 0 500 1000 1500 2000 2500 3000 3500 Elapsed Seconds b pass filter and b with 0 1 hertz low 107 4 4 Wireless ACPS Conclusions This chapter has introduced Autonomous Crack Propagation Sensing ACPS and evalu ated two types of commercially available crack propagation gages and a newly
32. are reproduced in their entirety as they existed on the Web at the time of publication of this document and without any modifica tion B 1 MICA2 Data Sheet MICA2 WIRELESS MEASUREMENT SYSTEM 3rd Generation Tiny Wireless Platform for Smart Sensors Designed Specifically for Deeply Embedded Sensor Networks gt 1 Year Battery Life on AA Batteries Using Sleep Modes Wireless Communications with Every Node as Router Capability 868 916 MHz Multi Channel Radio Transceiver Expansion Connector for Light Temperature RH Barometric Pressure Acceleration Seismic Acoustic Magnetic and other Crossbow Sensor Boards Applications Wireless Sensor Networks Security Surveillance and Force Protection Environmental Monitoring Large Scale Wireless Networks 1000 points Distributed Computing Platform 51 Pin Expansion Connector Antenna MMCX Connector MPR400 Block Diagram Phone 408 965 3300 Fax 408 324 4840 Crossb w MICA2 The MICA2 Mote is a third genera tion mote module used for enabling low power wireless sensor networks The MICA2 Mote features several new improvements over the original MICA Mote The following features make the MICA2 better suited to commercial de ployment 868 916 MHz multi channel transceiver with extended range Supported by MoteWorks wireless sensor network platform for reliable ad hoc mesh networki
33. can be any shape or size 4 3 1 Theory of Operation of Custom Crack Propagation Sensor The basic principles on which custom crack propagation gages function are similar to their pre fabricated counterparts an existing crack in a structure grows propagating over time through one or more rungs of the sensor As each rung breaks the resistance of the entire sensor in creases by a known value Using a precision excitation voltage and precision resistors of a known value each rung break can be obesrved by an Ko mote any other data logger as an increase in voltage Figure 4 16 shows a schematic of a custom crack propagation gage 4 3 2 Sensor Design Figure 4 16 indicates that the design calls for several resistors wired in parallel Though this could be implemented with individual precision resistors pre manufactured bus resistors an example of which is shown in Figure 4 17 provide a simpler and more reliable implementation Each bus resistor has ten pins One of the pins designated by a mark on the resistor housing is 100 Current Sensing Resistor Resistors of Known Value 54 9 250524 n lt gt 52 5254 lt gt 2 05 250505 5 2 52 9 6 250 lt lt SRE 25 5 lt gt lt 22 2555 9 gt SS x 5 c Conducti
34. ceilings in a wide variety of residential structures are between 8 and 15 hertz The HS 1 geophone has a minimum defined non shunted response frequency of approximately 1 5 hertz and is therefore well suited to measuring the expected structural response The GS 14 geophone with a minimum defined non shunted response frequency of 12 hertz is not as well suited but its smaller size makes it more attractive for installation in an occupied residential structure 3 3 6 2 Shake n Wake Design The Shake n Wake board shown in Figure 3 23 implements the same modular design and 15 the same size is the commercially available sensor boards manufactured by Crossbow It can therefore be attached to any MICA based wireless sensor mote by way of its standard 51 pin 63 connector Shake n Wake implements the hardware portion of the Lucid Dreaming strategy for event detection in energy constrained applications introduced by Jevtic et al 2007a Because of the single ended design of the low power analog comparator on which the Shake n Wake hardware is based the device cannot inspect both the positive and negative portions of any geophone output waveform using a single comparator To avoid ignoring either half of an input waveform the Shake n Wake board has two comparators and provides the user with two sensor input connectors CN3 and CN4 The output leads from the geophone are wired simultaneously to CN3 and CN4 but the connectors have opposite pola
35. do not possess expertise in computer science 30 computer engineering The hardware that composes a wired ACM system relies far less upon the user to configure the internals of the system and instead allows a focus on exactly what is desired to measure and the exact mechanism of measurement This chapter examines the process of selecting a WSN for use in a wireless ACM system selection of appropriate sensors for use with each type of WSN challenges in configuration and deployment of the systems and the fabrication of new hardware and software techniques to en able a wireless ACM system to more closely duplicate the functionality of its wired counterpart 3 2 Crack Displacement Sensor of Choice Regardless of the which WSN is to be used as a wireless ACM system changes in crack width must be measured Section 2 3 1 enumerates three different sensors that have been quali fied by previous researchers to adequately measure expected crack changes Table 2 1 summa rizes the differences between the operating characteristics of the three candidate sensors for a wireless ACM system The LVDT has the advantage in terms of sensor cost and in a situation in which out of plane motion is not expected the LVDT shows promise for the wireless ACM application especially since casual observation does not reveal a significant difference in power draw between the three sensors The eddy current gage has a clear advantage in footprint size and crack mot
36. floor to the third floor shown in Figure 3 30c These two motes were installed alongside optical crack measurement devices used for a different project The base station shown in Figure 3 30d was deployed in the basement underneath the kitchen 3 3 7 5 Results Figure 3 31 shows plots of temperature humidity battery voltage and parent mote over the entire deployment period Only Motes 3 and 4 transmit this data they are the only motes with an MDA300CA attached The plots indicate that after approximately 25 days of deployment 73 Node 0 Bose Node 4 2 8 Below Kitchen Floor 3rd Floor 81 4 above kitchen floor Nodes 1 and 2 Underside of Stairs 1 0 Below Kitchen Floor en uw Kitchen ffice 14757 ode 3 L Above doorway to stairs 8 7 Above Kitchen Floor 20 10 4 13 10 Figure 3 29 Layout of nodes in Version 3 test deployment the system ceased to take data Later examination indicated that this failure was due to an un foreseen software condition that caused the monitoring to stop prematurely At approximately day 75 a workaround was implemented each night the base station would automatically re broadcast the correct sampling interval Data transmission was restored immediately Mote 4 ceased taking data between days 85 and 115 for a reason that is not yet un
37. initiate crack growth Coupon A was instrumented with a narrow crack propagation pattern on one face as shown in Figure 4 11a Coupon B was instrumented with a wide crack propagation pattern on one face as shown in Figure 4 11b The wide pattern was too long to fit on the test coupon so the three rungs farthest away from the crack tip were removed before testing The initial reading would therefore indicate three rungs already having been broken before crack propagation began The crack propagation patterns on both Coupons A and B were affixed using the manufac turer s recommended solvent thinned adhesive cured at a temperature of at least 4 300 F This elevated temperature cure is not practical in the field so Coupon C was instrumented with a narrow pattern on one face and a wide pattern on the other face using epoxy cured at room temperature to determine if this would have a detrimental effect on ACPS functionality 94 25W 005W Dia 2 Holes Note 4 Y W 002W 1 25W 005W B Note 1 A Surfaces shall be perpendicular and as applicable to within 0 05 mm 0 002 in Note 2 Intersection of crack starter notch tip shail be equal distance between top and bottom of specimen edges within 0 5 mm 0 02 in Note 3 Integral or attached knife edges for clip gage at crack mouth may be used Note 4 For starter notch and fabigue crack configuration see Fig 7 Note 5 Loading pins
38. least six months e provided a more convenient operator interface e formed a self healing mesh network to increase both the range and the reliability of the wireless ACM system 3 3 5 1 Hardware Like Version 1 Version 2 consisted of several MICA2 motes equipped with MDA300CA sen sor boards and string potentiometers The only hardware difference between Version 1 and Version 2 was the replacement of the base station which in Version 1 simply relayed packets between a PC in the lab and the individual wireless motes with an embedded computer This computer called a Stargate Gateway and sold by Crossbow is a fully functional GNU Linux computer featuring an Ethernet port a CompactFlash slot and a connector for a single MICA2 mote Because the Stargate did not ship with an enclosure it was mounted to a plastic board as shown in Figure 3 10 Technical specifications of the Stargate may be found in Appendix B 5 Attached to household 110 V AC power the Stargate and the mote that was attached to it were always powered on and listening for data from the remote motes The data was recorded to the CompactFlash card where it was stored until the Stargate automatically transmitted the 47 59 hi bh ji 5 1 Figure 3 10 The Stargate Gateway mounted to a plastic board data back to the lab via the house s high speed Internet connection and standard Internet file transfer protocols 3 3 5 2 Software After the deployment and val
39. of any sensor to approximately 3 mV This resolution is suitable for measuring a rung break on the wide gage but it is not suitable for measuring the breakage of the first 10 12 rungs of the narrow 98 gage Figure 4 6a shows that the resistance change exhibited by a narrow gage for the first 10 12 rung breaks is significantly lower than that for the last 8 10 rung breaks therefore the voltage change exhibited by the readout circuit will also be lower for the first 10 12 rung breaks Two times over the course of the test the mote read momentary jumps in the voltage output of the wide gage and its readout circuit This same phenomenon was observed eleven times with the narrow gage This behavior is explained by noting that for any voltage input to the EKo mote s analog to digital conversion unit that falls on or near one of the 3 mV thresholds small amount of electromagnetic interference is capable of increasing or decreasing the voltage of the observed signal such that it could appear to have fallen into either of the two adjacent conversion regions It is also possible that since the crack and therefore the conductive portions of the gage were loaded cyclically intermittent contact may occur just before or after a rung had been broken Figure 4 14 shows that the adhesive cured at room temperature was not able to withstand the cyclic strains imposed by the fatigue test The lightly colored region indicated in Figure 4 14 shows where t
40. of 0 24W 0 000W 0 005W diameter FIG A1 1 Compact Tension Specimen for CTOA and Testing Figure 4 10 Schematic of compact test specimen W 3 5 in B 0 5 in after for Testing and Materials 2006 a b Figure 4 11 Test coupon with a narrow gage and b wide gage installed 4 2 2 1 Experimental Procedure After the fatigue cracking procedure was performed and the gages were affixed to the coupons each coupon was loaded into the mechanical testing machine and wired to either an Ko mote in 95 the case of Coupons A and a general purpose data logger and bench top power supply in the case of Coupon C The experiments on coupons A and B were designed to verify function ality of both the gages and the Ko motes but the experiment on Coupon C was designed solely to verify the performance of the sensor adhesion procedure Figure 4 12 shows a photograph of the experimental setup Figure 4 12 Photograph of experiment configuration for pre manufactured crack propagation gages During the approximately 80 minute tests the coupons were cyclically loaded between 0 07 kip and 2 5 kip at decreasing frequencies The crack in Coupon A propagated through all twenty rungs of the narrow gage as shown in Figure 4 13a while the crack in Coupon B propagated through eight rungs of the wide gage as shown in Figure 4 13b 96 b Figure 4 13 Test coupons with crack propagated through a narrow gage and
41. operating param eters either automatically or on demand 81 The inclusion of a cellular modem in the base station allows MICA2 based ACM system to be deployed anywhere with 110 V AC power within radio range of the sensor network Installation time is decreased with the added ability to put the motes into quick mesh mode to form the initial mesh network Installation is further simplified by the added ability to individually increase the sampling rate of a mote in order to more easily center the string potentiometer over a crack Shake Wake adds the ability for a MICA2 based wireless ACM mote to respond to a randomly occurring event of interest without sacrificing power A MICA2 based wireless ACM node should not be deployed without a MDA300CA sensor board even if the node does not need to measure the width of a crack The MDA300CA board and its drivers prevent the MICA2 based ACM system from fully implementing Mode 2 recording even when paired with Shake n Wake as its drivers do not fully support sampling rates of 1000 hertz Installation of a string potentiometer would be made less difficult if the MDA300CA had a software programmable front end gain the active range of the potentiometer decreases by 99 due to the front end gain on the MDA300 Software incompatibilities between the MDA300CA drivers and the Shake n Wake drivers cause the MDA300CA to take readings from the string potentiometer with a DC offset approximately 1
42. outside the structure Measurement on a single time scale of all of these quan tities in a given structure lends insight into the effects of both weather and nearby blasting or construction vibration on a structure A typical ACM system is designed to record these physical quantities throughout a structure not just in one particular location Figure 2 3 shows a scale drawing of a house in which a wired ACM system was installed Note that sensors are installed both indoors and outdoors upstairs and downstairs and separated in some cases by over 20 feet This type of layout is typical of ACM systems In the case of the system outlined in Figure 2 3 three engineers and a graduate student spent two full days in the home of a litigant drilling holes through interior and exterior walls pulling cables through an attic and gluing sensors to walls Because this type of system is most often installed in a home or place of business for months or years at a time minimization of intrusiveness and vulnerability of the ACM system is as crucial as minimization of cost and installation time This need to minimize simultaneously the cost the installation time and the overall disruptiveness of the ACM system leads directly to the necessity of wireless ACM high quality instrument cable can cost several dollars per foot and must be routed discretely through an occupied structure avoiding sources of electromagnetic interference and hazardous locations Cable installat
43. purchase price paid for the defective product as determined by Sherwin Williams NO OTHER WARRANTY OR GUARANTEE OF ANY KIND IS MADE BY SHERWIN WILLIAMS EXPRESSED OR IMPLIED STATUTORY BY OPERATION OF LAW OR OTHERWISE INCLUDING MER CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE www sherwin williams com protective 161
44. review This flow of data from physical measurements to a Web site is entirely autonomous and requires no human interaction In general if it can be shown that long term weather induced changes in crack width far exceed the vibration induced changes it can be concluded that the vibration is not in fact damaging the structure ACM systems were further refined and tested in the work of Louis 2000 McKenna 2002 Snider 2003 Baillot 2004 and Waldron 2006 The ACM systems described in this litera ture adhere to the general structure of computerized surveillance instrumentation as laid out by Dowding 1996 e transducers to measure ambient indoor and outdoor temperature ambient indoor and outdoor humidity ground or structural motion at a selected point or points changes in the widths of existing cracks in walls e centralized data logger to record data from all transducers e high quality instrument cable to carry signal from transducers to centrally located data logger The ACM system as described above is then connected usually via the Internet though rarely via the public telephone network to servers in the lab which automatically collect the readings and make them available on a Web site Figure 2 1 illustrates the flow of data from the sensors to interested parties The Internet connectivity of an ACM system also allows for remote reconfiguration of the system operating parameters which is essential for data management of
45. sensor manufacturer if that sensor is to be used with an eKo mote The crack propagation patterns are not compliant with the ESB so a customized interface cable was de signed built and installed The custom interface cable is composed of a Maxim DS2431 1024 Bit 1 Wire EEPROM a Switchcraft EN3C6F water resistant 6 conductor connector a length of Category 5e sold conductor cable one 3740 precision resistor and one 49 90 precision resistor The EEPROM was soldered into the water tight connector housing as shown in Figure 4 7 The EEPROM allows a sensor to respond with a unique sensor identifier when queried by an mote such that the sensor will be properly identified and configured automatically by any mote to which 91 it is connected After the EEPROM was mounted in the connector housing the individual cable leads were attached and the water tight cable assembly was completed as shown in Fig ure 4 8 This cable can be connected to any input port on any mote once the EEPROM is programmed with the appropriate information to operate the sensor Figure 4 7 Schematic of the EEPROM mounted in the watertight connector assembly after Crossbow Technology Inc 2009c COUPLING BOOT RING CABLE CABLE CLAMP CONTACT PINS O RING HOUSING MOLDED ONTO CORD CONNECTOR Figure 4 8 Watertight ESB compatible cable assembly after Switchcraft Inc 2004 When fully intact the narrow and wide crack propagation patterns have a
46. sherwin williams com protective 160 Protective amp Marine pa MACROPOXY 646 FAST CURE EPOXY SU Coati oatin S Part A B58 600 SERIES WILLIAMS 5 Part B B58V600 HARDENER Revised 2 10 APPLICATION BULLETIN 4 53 SURFACE PREPARATIONS APPLICATION CONDITIONS Surface must be clean dry and in sound condition Remove all oil dust grease dirt loose rust and other foreign material to ensure adequate adhesion Iron amp Steel Atmospheric Service Minimum surface preparation is Hand Tool Clean per SSPC SP2 Remove all oil and grease from surface by Solvent Cleaning per SSPC SP1 For better performance use Commercial Blast Cleaning per SSPC SP6 NACE 3 blast clean all surfaces using a sharp angular abrasive for optimum surface profile 2 mils 50 microns Prime any bare steel within 8 hours or before flash rusting occurs Iron amp Steel Immersion Service Remove all oil and grease from surface by Solvent Cleaning per SSPC SP1 Minimum surface preparation is Near White Metal Blast Cleaning per SSPC SP10 NACE 2 Blast clean all surfaces using a sharp angular abrasive for optimum surface profile 2 3 mils 50 75 microns Remove all weld spatter and round all sharp edges by grind ing Prime any bare steel the same day as it is cleaned Aluminum Remove all oil grease dirt oxide and other foreign material by Solvent Cleaning per SSPC SP1 Galvanized Steel Allow to weather a minimum of six months
47. the IR technical white paper Milliamp Hours Capacity Constant Current Discharge to 0 9 Volts at 21 C 50 50 1 988 49 50 1 949 4000 mAA Lithium Alkaline 3000 0 10 0 004 I 7 00 0 276 Typical Minimum AY i 25 250 500 Capacity mAh 5 8 This battery has Underwriters 1000 peser 55980 Discharge mA Milliwatt Hours Capacity at Cold Room Temperature Constant Power Discharge to 1 0 Volts at 0 C and 21 C Cold Temperature 0 C Room Temperature 21 C 5000 Constant Power Discharge 5000 Constant Power Discharge Lithium Alkaline Lithium Alkaline 4000 4000 4 E E 3000 3000 gt 1 5 2000 5 2000 8 8 1000 4 1000 0 T T 0 T 1 50 250 500 1000 50 250 500 1000 Discharge mW Discharge mW Important Notice This datasheet contains typical information specific to products manufactured at the time of its publication GEnergizer Holdings Inc Contents herein do not constitute a warranty Form No EBC 4201P Page 1 of 2 144 PRODUCT DATASHEET Energizer 1 800 383 7323 US CAN www energizer com ENERGIZER L91 Typical Discharge Curve Characteristics Constant Current Discharge at 21 C low and high drains Low Drain Performance Hi
48. the appropriate times Secondly these types of events require high frequency sampling to capture their true nature Siebert 2000 indicates that these types of dynamic phenomena can last for three to fifteen seconds and must be recorded at one thousand samples per second to fully resolve all high frequency motion In order to capture the entire dynamic event some of which may occur at a time before the peak of the input signal exceeds the trigger threshold ACM systems utilize buffering to avoid losing the pre trigger data At any given time an ACM system has a buffer typically one half to a full second of data sampled one thousand times per second stored in its memory If a threshold crossing condition does not occur the data is discarded If a crossing does occur however then the pre trigger data is concatenated to the post trigger data to form a single time history that clearly shows the point at which the trigger threshold was crossed The issue of when a dynamic event should be recorded is non trivial The occurrence of a random event is determined by the data logger continuously measuring the output of a geophone or geophones and using its microprocessor to compare the current geophone output to the pre programmed threshold value If the threshold value is set too low the system will be overloaded with data that then must be transmitted back to the lab If the value is set too high the system will fail to record an event of interest For
49. the node with the string poten tiometer was not configured to measure a crack but instead was configured in the manner of a donut qualification test as described in Baillot 2004 In this this configuration instead of measuring the change in width of a crack in a wall the string potentiometer measures the ther mal expansion and contraction of a plastic ring or donut as shown in Figure 3 15 The node measuring the donut was placed on the sun porch to ensure exposure to maximum temperature differences and therefore achieve the largest possible expansion and contraction of the donut Finally alkaline batteries were used in the deployment test instead of lithium batteries Al though alkaline batteries have less capacity than lithium batteries especially when operating in 52 b d Figure 3 13 MICA2 based wireless ACM Version 2 nodes located a in the basement b on the sun porch c in the apartment and d over the garage colder temperatures Energizer Holdings 2010a their voltage output decreases over time such that the remaining battery life might be estimated The voltage output of lithium batteries tends to stay steady over time then drop rapidly at the end of their working capacity Energizer Hold ings 2010b It was therefore expected that the total service life of the wireless sensor network might decrease from the ideal estimate of 384 days to 150 200 days 53 Figure 3 15 A string potentiomet
50. their components see Ozer 2005 In the remainder of this document a mote shall refer to the actual processor radio board device while a node shall refer to the combination of mote sensor board s external to the mote and sensors deployed at a specific location in a structure 3 1 1 2 Base Station At minimum the base station is responsible for receiving by radio all of the transmissions that originate from within the wireless sensor network then relaying this data through some other communication mechanism back to interested parties In most cases though the base station of a WSN contains the majority of intelligence of the system More sophisticated base stations have provisions for on board data storage and analysis and provision of a control interface by which a remote user might reconfigure the WSN after it has been deployed in the field Some base stations provide a Web based interface for control of the network provide the ability to process and analyze data and make available the ability to send alerts to interested parties Some WSN systems require this base station to be connected to a personal computer others support direct connection to the Internet 27 3 1 1 3 Wireless Communication Each mote is equipped with a radio that allows it to send and receive data to and from both other motes and the base station In the simplest possible WSN each mote transmits its data directly to the base station whenever data
51. xbow com 133 adio Board Processor Performance Program Flash Memory 128K bytes Measurement Serial Flash 512K bytes 100 000 Measurements Configuration EEPROM 4K bytes Serial Communications UART 0 3V transmission levels Analog to Digital Converter 10 bit ADC 8 channel 0 3V input Other Interfaces DIO I2C SPI Current Draw 8mA Active mode lt 15 pA Sleep mode Multi Channel Radio Center Frequency 868 916 MHz ISM bands Number of Channels 4 50 Programmable country specific Data Rate 38 4 Kbaud Manchester encoded RF Power 20 to 5 dBm Programmable typical Receive Sensitivty 98 dBm Typical analog RSSI at AD Ch 0 Outdoor Range 500 ft 1 4 Wave dipole line of sight Current Draw 27 mA Transmit with maximum power 10 mA Receive lt 1pA Sleep Electromechanical Battery 2X AA batteries Attached pack External Power Connector provided User Interface 3 LEDs User programmable Size 2 25x1 25x0 25 Excluding battery pack mm 58x32x7 Excluding battery pack Weight o2 07 Excluding batteries grams 18 Excluding batteries Expansion Connector 51 pin All major I O signals Notes Specifications subject to change without notice Base Stations A base station allows the aggregation of sensor network data onto a PC or other computer platform Any MICA2 Mote can function as a base station when it is connected to a standar
52. 09b 3 2 Photograph of a string potentiometer with quarter for scale after Jevtic et al 2007b 3 3 Photograph of a fully mounted string potentiometer after Ozer 2005 3 4 Photograph of a Crossbow MICA2 mote with quarter for scale 3 5 Photograph of a Crossbow 510 serial gateway with MICA2 without batteries installed after Ozer 2005 3 6 Photograph of a Crossbow MDA300 with quarter for scale after Dowding et al 2007 37 Photographs of Version 1 of the MICA2 based wireless ACM system after Ozer 2005 a base station in closet b node on ceiling monitoring crack 3 8 Temperature and crack displacement measurements by wireless and wired ACM systems in test house over two month period after Ozer 2005 3 9 Alkaline battery voltage decline of a mote running MDA300Logger after Ozer 2005 3 10 The Stargate Gateway mounted to plastic board 23 28 32 33 34 35 36 40 43 44 47 3 11 3 12 3 13 3 14 315 3 16 3 17 3 18 3 19 3 20 3 21 3 22 3 23 3 24 3 25 xvii Current draw profile of a mote running the modified XMDA300 software for Mode 1 recording the periodic sampling window is shown in the dashed oval in the inserted figure demonstrating intermittent operation compared to ongoing operation after Dowding et al 2007 50 Distribution of sensor nodes throughout test structures 51 MICA2 based wireless ACM Version 2 nodes loca
53. 1nuoqq 150 200 100 Days Deployed a Donut Expansion vs Temperature Week 0 2 lt 2 e e e T T T T i Las Ss E B o L m d E d 4 ea SSS EN d a 1 E ieee 26 96 e en en e e N N uorsuedxg muoq 107 106 105 104 103 02 1 101 100 Days Deployed b Plot of temperature versus donut expansion over a period of a 200 days and b one week Figure 3 17 Temperature vs Days Deployed 60 T T T Temperature deg C 10 1 1 1 1 1 0 50 100 150 200 250 300 Days Deployed Figure 3 18 Plot of each Version 2 wireless ACM mote s temperature versus time Humidity vs Days Deployed Humidity 20 1 1 4 1 1 0 50 100 150 200 250 300 Days Deployed Figure 3 19 Plot of each Version 2 wireless ACM mote s humidity versus time 57 58 Transmitting Mote Mote 1 Mote 2 Mote 3 Mote 4 Total Base 1519 17 8583 91 8481 90 8174 87 26 757
54. 2 000 hours ASTM D610 per rusting Direct Impact Resistance ASTM D2794 30 in Ib Dry Heat Resistance ASTM 02485 250 F 121 C Exterior Durability 1 year at 45 South Excellent chalks ASTM 0522 180 bend Flexibility Passes Humidity Resistance ASTM 04585 6000 No blistering cracking or hours rusting 1 year fresh and salt Passes no rusting water blistering or loss of adhesion Irradiation Effects on Coatings used in ANSE S12 851M Passes Nuclear Power Plants 04082 89 Pencil Hardness ASTM D3363 3H Rating 10 per ASTM 0610 for rusting Rating 9 per Salt Fog Resistance ASTM B117 6 500 hours ASTM 01654 for corrosion Specification for Struc wee mat tural Joints Using ASTM Class A 0 36 A325 or ASTM A490 Bolts Water Vapor Permeance ASTM D1653 Method B 1 16 US perms Epoxy coatings may darken or discolor following application and curing Footnotes Zinc Clad Plus Primer www sherwin williams com protective continued on back 159 Protective o amp Marine Coatings SHERWIN WILLIAMS PRODUCT INFORMATION MACROPOXY 646 FAST CURE EPOXY Part A B58 600 SERIES Part B B58V600 HARDENER 4 53 RECOMMENDED SYSTEMS Dry Film Thickness ct Mils Microns Immersion and atmospheric Steel 2cts 646 5 0 10 0 125 250 Concrete Masonry smooth 2cts 6
55. 2 No 60950 1 03 TUV EN60950 1 Reliability Alert Tools Built in buzzer and RTC real time clock Automatic Reboot Trigger Built in WDT watchdog timer Warranty Warranty Period 5 years Details See www moxa com warranty www moxa com info moxa com gt gt Embedded Computers um Software Specifications Linux Kernel Version 2 6 10 Protocol Stack TCP UDP IPv4 SNMP V1 ICMP IGMP ARP HTTP CHAP PAP SSH 1 0 2 0 SSL DHCP NTP NFS SMTP Telnet FTP PPP PPPoE File System JFFS2 on board flash System Utilities bash busybox tinylogin telnet ftp scp telnetd Telnet Server daemon ftpd FTP server daemon sshd Secure shell server Apache Web server daemon supporting PHP and XML openvpn Virtual private network service manager iptables Firewall service manager pppd dial in out over serial port daemon amp PPPoE snmpd snmpd agent daemon inetd TCP server manager program Application Development Software Moxa Linux API Library for device control Linux Tool Chain Gcc Glibc GDB Windows Embedded CE 5 0 System Utilities Windows command shell telnet ftp web based administration manager Dimensions unit mm File System FAT on board flash Protocol Stack TCP UDP IPv4 IPv6 Tunneling SNMP V2 ICMP IGMP ARP HTTP CHAP PAP SSL DHCP SNTP SMTP Telnet FIP PPP Telnet Server Allows remote administration through a standard telnet client FTP Server Used fo
56. 2 hours To recoat minimum 16 hours 4 hours 2 hours maximum 1 year 1 year 1 year Application of coating above maximum or below minimum recommended spreading rate may adversely affect coating performance CLEAN UP INSTRUCTIONS Clean spills and spatters immediately with Reducer R7K15 Clean tools immediately after use with Reducer R7K15 In California use Reducer R7K111 Follow manufacturer s safety recommendations when using any solvent PERFORMANCE TIPS Stripe coat all crevices welds and sharp angles to prevent early failure in these areas When using spray application use a 50 overlap with each pass ofthe gun to avoid holidays bare areas and pinholes If necessary cross spray at a right angle Spreading rates are calculated on volume solids and do not include an application loss factor due to surface profile roughness or po rosity of the surface skill and technique of the applicator method of application various surface irregularities material lost during mixing spillage overthinning climatic conditions and excessive ilm build Excessive reduction of material can affect film build appearance and adhesion Do not mix previously catalyzed material with new Do not apply the material beyond recommended pot life In order to avoid blockage of spray equipment clean equipment before use or before periods of extended downtime with Reducer R7K15 In California use Reducer R7K111 Tinting is not recommen
57. 200 Anm MAX 124 li 250 BOTH ENDS 049 508 050 200 020 002 YP 254 07 L NEA 100 008 4610X NON ACCUM Pin A Maximum 4 00 2508 Count mm Inches 4 10 11 398 5 12 65 498 OR 249 MAX 6 15 19 598 P 7 17 73 698 8 20 27 798 9 22 81 898 0 25 70 125 10 25 35 998 AMBIENT TEMPERATURE C 27 89 1 088 S IESUS 0104 002 14 35 51 1 398 Package Power Ratings Watts Ambient Ambient Temperature Temperature Pkg 70 C Pkg 70 C 4604X 0 50 4610X 1 25 4605X 0 63 4611X 1 38 4606X 0 75 4612X 1 50 4607X 0 88 4613X 1 63 4608X 1 00 4614X 1 75 4609X 113 Typical Part Marking Represents total content Layout may vary Part Number Part Number 4606X 101 RC 6X 1 RC 4608X 102 RC 8X 2 RC 4610X 104 RC RC 10X 4 RC RC RC ohmic value 3 digit resistance code CIRCUIT RESISTANCE CODE NUMBER OF PINS DATE CODE MANUFACTURER S TRADEMARK PIN ONE INDICATOR Maximum package length is equal to 2 54mm 1007 times the number of pins less 005mm 002 Governing dimensions are in metric Dimensions in parentheses are inches and are approximate Terminal centerline to centerline measurements made at point of emergence of the lead from the body For Standard Values Used in Capacitors Inductors and Resistors click here RoHS Directive 2002 95 EC Jan 27 2003 includi
58. 2200MTP 8 5g 0 3 oz MicroTip 0 8 mm tip TECHNICAL amp APPLICATION ASSISTANCE Chemtronics provides a technical hotline to answer your technical and application related questions The toll free number is 1 800 401 NOTE This information is believed to be accurate It is intended for professional end users having the skills to evaluate and use the data properly ITW CHEMTRONICS does not guarantee the accuracy of the data and assumes no liability in connection with damages incurred while using it MANUFACTURED BY ITW CHEMTRONICS 8125 COBB CENTER DRIVE KENNESAW GA 30152 1 770 424 4888 REV F 06 09 DISTRIBUTED BY 158 13 Bridge Paint Data Sheet Protective amp Marine MACROPOXY 646 FAST CURE EPOXY Coatin S Part A B58 600 SERIES WILLIAMS 5 Part B B58V600 HARDENER Revised 2 10 PRODUCT INFORMATION dis DESCRIPTION CHARACTERISTICS MACROPOXY 646 FAST CURE EPOXY is a high solids high build fast drying polyamide epoxy designed to protect steel and concrete in industrial exposures Ideal for maintenance painting and fabrica tion shop applications The high solids content ensures adeguate protection of sharp edges corners and welds This product can e applied directly to marginally prepared steel surfaces Low Chemical resistant Low odor Abrasion resistant Outstanding application p
59. 3 5 2 3 3 5 3 3 3 5 4 3 3 5 5 3 3 5 6 2 20 3 3 6 1 3 3 6 2 3 3 7 3 3 7 2 8272 3 3 7 4 3375 3 3 7 6 3 3 8 Operation Deployment in Test Structure Results MICA2 Based Wireless ACM Version 2 XMesh Hardware Software Analysis of Power Consumption Deployment in Test Structure Results Discussion MICA2 Based Wireless ACM Version 3 Shake n Wake Geophone Selection Shake n Wake Design Hardware Software Operation Analysis of Power Consumption Deployment in Test Structure Results Discussion Wireless ACM Conclusions Chapter 4 Techniques for Wireless Autonomous Crack Propagation Sensing 4 Chapter Introduction ix 41 42 44 46 46 47 49 49 54 55 60 61 62 65 67 69 70 12 70 76 80 83 83 4 1 1 Visual Inspection 84 4 1 2 Other Crack Propagation Detection Techniques 86 4 3 The Wireless Sensor Network 87 4 2 ACPS Using Commercially Available Sensors 88 4 2 1 Integration with Environmental Sensor Bus 89 4 2 2 Proof of Concept Experiment 923 4 2 2 1 Experimental Procedure 94 4 2 3 Results and Discussion 97 4 3 Custom Crack Propagation Gage 98 4 3 1 Theory of Operation of Custom Crack Propagation Sensor 99 4 3 2 Sensor Design 99 4 3 3 Proof of Concept Experiment 103 4 3 4 Results and Discussion 105 4 4 Wireless ACPS Conclusions 107 Chapter 5 Conclusion 109 5 Conclusion 109 5 2 Future Work 111 5 2 Wireless Autono
60. 4 25 0004 20 0004 a 192007 vu 10 0004 oi x 5 0005 2 2 41 42 43 744 45 4 4n 48 Exterior Null Gauge nes 35 0005 30 0005 25 0005 20 000 3 15 000 inm erm 5 000 7 1 1 41 42 43 44 45 46 47 48 23 we 122108 124236 120264 1400 1220 129 2 000 malhseconcts 2005 1631 74328 72456 12584 741712 7 024 750 1 000 1250 1 0 179 2 000 Jan 18 2051631 098 10 1512 10 0646 A 99714 9592 9 803 79 1 000 1250 1 500 179 2 000 Figure 2 11 Screen shots of long term correlation of crack width and humidity from Mode 1 recording b crack displacement waveforms from Mode 2 recording 24 2 6 Chapter Conclusion This chapter has shown that for the purposes of monitoring crack activity as caused by vibra tion mining or weather different types of sensors may be used to measure crack displacement Choice of sensor type is determined by constraints on the availability of power precision exci tation and physical space for sensor installation By combining Mode 1 and Mode 2 recording the effects of long term changes in temperature and humidity can be compared to the dynamic effects of vibration and household activity Both modes are essential to the true quantification of the effects of vibration on residential structures This chapter has also shown that direct monitoring of crack elongation or pro
61. 4 shows MICA2 mote with a quarter for scale Figure 3 4 Photograph of a Crossbow MICA2 mote with quarter for scale 3 3 1 The Mote The MICA2 mote Crossbow model number MPRAOOCB 15 a third generation mote module used for enabling low power wireless sensor networks Crossbow Technology Inc 20072 The MICA2 features an industry standard ATmegal128L low power microcontroller which is powerful enough to run sensor applications while maintaining radio communication with the base station and other motes It also features a 10 bit ADC and a 51 pin connector and support for several digital communication protocols for connecting to other Crossbow and third party manufactured sensor boards Finally it features a multi channel radio with a nominal 500 foot 35 line of sight transmission range The MICA2 arrives from the manufacturer configured to use two standard AA cell batteries The MICA2 mote is designed to operate with a Crossbow MIB510CA Serial Gatway This device pictured in Figure 3 5 serves the dual purposes of acting as a programming board to load software onto a MICA2 and acting as part of a base station that will when paired with an appropriately programmed MICA2 mote receive data from the wireless network and relay them via RS 232 to either a local embedded field computer or directly over the Internet back to the lab Figure 3 5 Photograph of a Crossbow MIB510CA serial gateway with MICA2 without bat teries ins
62. 46 5 0 10 0 125 250 Concrete Block 1ct Kem Cati Coat HS Epoxy 10 0 20 0 250 500 Filler Sealer as needed to fill voids and provide a continuous substrate 2cts 646 5 0 10 0 125 250 Atmospheric Steel Shop applied system new construction AWWA D102 03 can also be used at 3 mils minimum dft when used as an intermediate coat as part of a multi coat system 1ct Macropoxy 646 Fast Cure Epoxy 3 0 6 0 75 150 1 2 cts of recommended topcoat Steel 1ct Recoatable Epoxy Primer 4 0 6 0 100 150 2cts 646 5 0 10 0 125 250 Steel 1 ct Macropoxy 646 4 0 6 0 100 150 1 2 cts Acrolon 218 Polyurethane 3 0 6 0 75 150 or Hi Solids Polyurethane 3 0 5 0 75 125 or SherThane 2K Urethane 2 0 4 0 50 100 or Hydrogloss 2 0 4 0 50 100 Steel 2cts 646 5 0 10 0 125 250 1 2 cts Tile Clad HS Epoxy 2 5 4 0 63 100 Steel 1 ct Zinc Clad 1 Plus 3 0 6 0 75 150 1ct Macropoxy 646 3 0 10 0 75 250 1 2 cts Acrolon 218 Polyurethane 3 0 6 0 75 150 Steel 1ct Zinc Clad HS 3 0 5 0 75 125 or Zinc Clad IV 3 0 5 0 75 125 1ct Macropoxy 646 3 0 10 0 75 250 1 2 cts Acrolon 218 Polyurethane 3 0 6 0 75 150 Aluminum 2cts 646 5 0 10 0 125 250 Galvanizing 2cts 646 5 0 10 0 125 250 The systems sted above are representative of the product s use other systems may be appropriate DISCLAIMER
63. 5 Geo Space Corporation 1996 HS 1 LT 4 5Hz 1250 Ohm Horiz Part number 98449 Hopwood T 2008 Personal communication with University of Kentucky researcher Hopwood T and Prine D 1987 Acoustic emission monitoring of in service bridges Tech nical Report UKTRP 87 22 Kentucky Transportation Research Program University of Ken tucky Lexington Kentucky ITW CHEMTRONICS 2009 CircuitWoprks Conductive Pen TDS Num CW2200 Jevtic S Kotowsky M P Dick R P Dinda P A and Dowding C H 2007a Lucid dreaming Reliable analog event detection for energey constrained applications In Proc IPSN SPOTS 2007 Cambridge Massachusetts Association for Computing Machinery In stitute of Electrical and Electronics Engineers Jevtic S Kotowsky M P Dick R P Dinda P A Dowding C H and Mattenson M J 2007b Lucid dreaming Reliable analog event detection for energey constrained applica tions Poster presented during live demonstration 115 Kaman Measuring Systems 2009 Sensor data sheet SMU 9000 http www kamansensors com html products pdf wSMU9000 9200 pdf Kosnik D 2007 Internet enabled geotechnical data exchange In Proc 7th Int l Sympo sium on Field Measurements in Geomechanics Boston Massachusetts American Society of Civil Engineers Kotowsky M P 2010 Wireless sensor networks for monitoring cracks in structures Source code and configuration files Addendum to MS Thesis
64. 5 of the time These anomalous readings can be filtered out in post processing The Shake n Wake hardware design and a software implementation of the Lucid Dreaming strategy for random event detection in energy constrained systems are not 82 uniquely compatible with the MICA2 MDA300CA system described in this chapter they can be ported to any wireless sensor network that allows for direct physical ac cess to the interrupt lines on the control processor and proper access to the low level software Unfortunately many commercially available systems designed for ease of use for novice users do not provide such access thus Shake n Wake Lucid Dreaming integration must be performed at the factory and not by the end user 83 4 Techniques for Wireless Autonomous Crack Propagation Sensing 4 1 Chapter Introduction Autonomous Crack Propagation Sensing ACPS is a measurement technique designed to record the propagation of slow growing structural cracks over long periods of time In contrast to ACM ACPS does not seek to directly correlate crack extension to any other physical phe nomena rather ACPS seeks to record quantitatively repeatably and accurately the extension of cracks in structures specifically to supplement regular inspections of bridges An ACPS system allows structural stakeholders to be alerted to crack extensions with ample time to ensure the safety of the structure and those using it Though ACPS techniq
65. 83 7323 USA CAN www energizer com ENERGIZER E91 Specifications Classification Alkaline nerguzer Chemical System Zinc Manganese Dioxide Zn MnO 3 No added mercury cadmium Designation ANSI 15A IEC LR6 Nominal Voltage 1 5 volts Pi 5 Nominal IR 150 to 300 milliohms fresh Industry Standard Dimensions Operating Temp 18 C to 55 C 0 F to 130 F mm inches Typical Weight 23 0 grams 0 8 02 gt Typical Volume 8 1 cubic centimeters 0 5 cubic inch SN Jacket Plastic Label Shelf Life 7 years at 21 C 80 of initial capacity Terminal Flat Contact a __14 50 0 571 13 50 0 531 For additional information please reference the IR technical white paper 1 00 0 039 d 550 021 oo poas Maximum ot eT Milliamp Hours Capacity Continuous discharge to 0 8 volts at 219C 3000 50 50 1 988 2500 49 50 1 949 1500 4 1000 4 500 AL 0 r 25 100 250 500 0 10 6005 I 7 00 0 276 Typical Minimum Capacity mAh Discharge mA Device Selection Guide Battery Selection Indicator High Drain Photoflash Devices Games CD s MD s Player D Lighting Moderate 4 Drain Devices Toy Remote Control __ Low Drain Devices Clock Important Notice This data sheet contains typical information specific to products manufactured at the time of its publication GEnergizer Holdings Inc
66. A driver software and allow the driver to dictate the interval at which samples are taken Because the available intervals were not long enough to implement Mode 1 recording XMDA300M nc was modified such that it has its own timer that starts and stops the SamplerControl module thereby putting the MDA300CA into its lowest power state when not sampling The main application will start the MDA300CA instruct it to get samples quickly wait for one set of readings to be completed send those readings up the network then completely shut down the MDA300CA until the next sample should be read If the MDA300CA driver itself were responsible for managing the interval timings the mote would never enter its lowest power mode severely limiting the operational lifetime The application was built using the same development tool chain by which the original XMDA300 application was built The software utilizes low power listening mode the second lowest power mode that XMesh is able to provide Crossbow Technology Inc 2007e To facilitate ease of installation when the motes are first turned on the first sixty readings are sent out once per minute This allows the multi hop mesh network to form or fail to form 49 within several minutes so that the installer has time to reconfigure the network if necessary Without this modification several hours would be required to determine whether a network layout would be functional 3 3 5 3 Analysis of Power
67. B sensor output is measured between C and B 100 Photograph of a commercially available bus resistor after Bourns 2006 100 Predicted change in output voltage of custom crack propagation sensor with rungs broken 102 Photograph of an engineer applying a custom crack propagation gage 104 Photograph of coupon with attached custom crack propagation gage 104 Coupon with custom gage after all rungs broken 105 Custom crack gage output versus time a unfiltered and b with 0 1 hertz low pass filter 106 A 2 A 3 A 4 A 5 A 6 A 7 A 8 A 9 xxi Shake n Wake transparency test apparatus 119 Shake n Wake transparency test results for HS 1 geophone 120 Shake n Wake trigger threshold test apparatus 121 Shake n Wake Level 2 trigger threshold test results for HS 1 geophone at 5 hertz 121 Shake 7 Wake Level 2 trigger threshold test results for GS 14 geophone at 5 hertz 122 Summary of Shake n Wake level 2 trigger threshold voltages 123 Summary of Shake n Wake level 2 trigger threshold velocities 125 20 hertz sinusoidal input signal with rise time of 12 5 milliseconds 126 Scope readout indicating the mote can execute user code within 89 us of a signal of interest after Jevtic et al 2007b 128 CHAPTER 1 Introduction Autonomous Crack Monitoring ACM and Autonomous Crack Propagation Sensing ACPS are two autonomous structural health monitoring techniques performed on two different types structur
68. California Reducer R7K111 Airless Spray Pump 30 1 Pressure 2800 3000 psi Hose 1 4 ID Tip 017 023 Filter 60 mesh Reduction As needed up to 10 by volume Conventional Spray Ubi otioso DeVilbiss MBC 510 Fluid Tip E Air Nozzl 704 Atomization Pressure Fluid Pressure Reduction As needed up to 10 by volume Requires oil and moisture separators Brush Brush Nylon Polyester or Natural Bristle Reduction Not recommended Roller Cover 3 8 woven with solvent resistant core Reduction Not recommended If specific application equipment is not listed above equivalent equipment may be substituted www sherwin williams com protective continued on back Protective amp p MACROPOXY 646 FAST CURE EPOXY Marine SHERWIN atin PART B58 600 SERIES WILLIAMS Co gs Part B B58V600 HARDENER APPLICATION BULLETIN 453 APPLICATION PROCEDURES Surface preparation must be completed as indicated Mix contents of each component thoroughly with low speed power agitation Make certain no pigment remains on the bottom of the can Then combine one part by volume of Part A with one part by volume of Part B Thoroughly agitate the mixture with power agitation Allow the material to sweat in as indicated prior to ap plication Re stir before using If reducer solvent is used add only after both components have been th
69. Consumption To calculate the power draw of a mote using the ACM modified version of XMDA300 a sim ple ammeter circuit was implemented by placing a 10 ohm resistor in series with the positive terminal of the battery on the mote By reading the voltage across this resistor the current draw of the mote can be calculated recorded and compared to the total theoretical power capacity of a pair of lithium AA batteries in series 3000 mAh at 3 V DC Energizer Holdings 2010b Appendix B 7 Figure 3 11 shows the current draw profile of a single mote The current readings were recorded at 10 hertz and averaged to determine the average cur rent used by the mote during a period of 18 hours The average current draw when the mote is sampling once per hour is 325 uA Since the total current capacity of the battery pack is 3000 mAh the total estimated lifespan is estimated to be approximately 384 days assuming the first hour of higher frequency sampling is ignored 3 3 5 4 Deployment in Test Structure A deployment test of Version 2 of the MICA2 based wireless ACM system was conducted in a century old historic house near the Northwestern campus The objective of the test was to determine the degree of difficulty of the installation of the system the effectiveness of the XMesh routing layer to create and maintain a low power multi hop network and a projection for the true system deployment lifetime before batteries must be changed 50 Sampling
70. ESB interface cable a customized data inter pretation file for each type of crack propagation sensor was created and stored on the base station These files found in the separate document Kotowsky 2010 need only to be created once by the sensor manufacturer and do not need to be created or maintained by the end user of the ACPS system 93 4 2 2 Proof of Concept Experiment A proof of concept experiment was designed to test both the effectiveness of the crack propa gation gages in measuring fatigue cracking in steel and the eKo motes ability to reliably and accurately read the sensors Three 3 5 in by 3 5 in by 0 5 in ASTM E2472 compact tension test coupons A B and C a schematic of which is shown in Figure 4 10 were fabricated from A36 steel These coupons were placed in a mechanical testing apparatus to apply cyclic tensile forces at their circular attachment points to propagate a crack through the specimens and the gages Before each coupon was instrumented with a crack propagation pattern a fatigue crack was initiated in each one under the assumption that any crack to be instrumented in the field would have begun to grow before the sensor is affixed During the pre cracking procedure the relative displacement of the attachment points was cycled between 0 24 inches and 0 0016 inches at a frequency of 10 hertz until a crack was observed to be growing from the tip of the wire cut notch Approximately 10 000 cycles were required to
71. Figures Chapter 1 Introduction Chapter 2 Fundamentals of the Monitoring of Cracks 2 1 Overview of Autonomous Crack Monitoring 2 2 Crack Width 2 3 A Wired ACM System 2 3 Crack Width Sensors 2 3 2 Velocity Transducers 2 3 2 1 Traditional Buried Geophones 2 3 2 2 Miniature Geophones 2 3 3 Temperature and Humidity Sensors 2 4 Types of Crack Monitoring 2 4 1 Width Change Monitoring 2 4 1 1 Mode 1 Long term vii iii xiii XV 10 13 13 14 15 15 16 17 Vili 2 4 1 2 ACM Mode 2 Dynamic 2 4 2 Crack Extension Monitoring 2 4 2 1 Traditional Crack Propagation Patterns 2 4 2 2 Custom Crack Propagation Patterns 2 5 Examples of the output of an ACM system 2 6 Chapter Conclusion Chapter 3 Techniques for Wireless Autonomous Crack Monitoring 3 1 Chapter Introduction 3 1 1 Wireless Sensor Networks 3 1 1 1 Motes 3 1 1 2 Base Station 3 1 1 3 Wireless Communication 3 1 2 Challenges of Removing the Wires from ACM 3 2 Crack Displacement Sensor of Choice 3 3 WSN Selection 3 3 1 The Mote 3 3 2 Sensor Board Selection 3 3 2 1 Precision Sensor Excitation 3 3 2 2 Precision Differential Channels with 12 bit ADC 3 3 3 Software and Power Management 3 3 4 MICA2 Based Wireless ACM Version 1 3 3 4 1 Hardware 3 3 4 2 Software 17 20 21 21 22 24 42 25 25 26 26 27 27 30 33 34 35 37 37 38 38 38 41 3 3 4 3 3 3 4 4 3 3 4 5 3 3 5 303 94 3
72. Hakemian the tenants of the third floor apartment for allowing me to place a wireless sensor node in their home for several months Professors Peter Dinda and Robert Dick of Northwestern University s Department Electri cal Engineering and Computer Science led a team of engineering undergraduates and gradu ate students faculty and staff in a collective research group funded by the National Science Foundation under award CNS 0721978 They acted in an advisory role to Sasha Jevtic in the Shake n Wake project described in Chapter 3 and provided the funds to purchase the eKo Pro Series WSN described in Chapter 4 Their insightful commentary and advice aided greatly in my software work Sasha Jevtic a graduate student then graduate of Northwestern University s Electrical and Computer Engineering Department was the chief developer of the Shake n Wake board de scribed in Chapter 3 Mr Jevtic brought to the project not only his considerable electronics and engineering expertise but the willingness to spend late nights in the lab with me debugging hardware and software after we had both finished working full days vi Mark Seniw of Northwestern University s Department of Materials Science and Engineer ing was crucial in performing the experiments described in Chapter 4 With his extensive expe rience in mechanical testing Mr Seniw guided me through every step of the process of creating then destroying compact test specimens and dedicated a
73. NORTHWESTERN UNIVERSITY Wireless Sensor Networks for Monitoring Cracks in Structures A THESIS SUBMITTED TO THE GRADUATE SCHOOL IN PARTIAL FULFILLMENT OF THE REQUIREMENTS for the degree Master of Science Field of Civil Engineering By Mathew Kotowsky EVANSTON ILLINOIS June 2010 ABSTRACT Autonomous Crack Monitoring ACM and Autonomous Crack Propagation Sensing ACPS are two types of structural health monitoring in which characteristics of cracks are recorded over long periods of time ACM seeks to correlate changes in widths of cosmetic cracks in structures to nearby blasting or construction vibration activity for the purposes of litigation or regulation ACPS seeks to track growth of cracks in steel bridges supplementing regular inspections and alerting stakeholders if a crack has grown Both ACM and ACPS may be implemented using wired data loggers and sensors however the cost of installation and intrusion upon the use of a structure makes the use of these sys tems impractical if not completely impossible This thesis presents the implementation of these systems using wireless sensor networks WSNs and evaluates the effectiveness of each Three wireless ACM test deployments are presented the first a proof of concept the second to show long term functionality and the third to show the effectiveness of a newly invented device for low power event detection Each of these case studies was performed in a residential
74. O 2I6 52 SWHO gest SNIdWYO 5 00 BBE 002 091 ATIA Se inainn VAC NT SAY 148 B 9 HS 1 Geophone Data Sheet SENSING SYSTEMS ENGINEERING PRODUCT CUSTOMER SPECIFICATION FOR HS 1 LT 4 5Hz 1250Q Horizontal Geo Space Corporation 1991 GEO SPACE CORPORATION PROPRIETARY NOTICE Houston Texas U S A DATE DWN This document whether patentable or non patentable 11 14 96 TITLE subject matter embodies proprietary and confidential HS 1 LT 4 5Hz 12500 Horiz information and is the exclusive property of Geo Space Corporation It may not be reproduced used or disclosed CHECK BY to others for any purpose except that for which it is loaned and it shall be returned on demand SHEET OF 3 SPECIFICATION REV S 98449 A 149 PRODUCT CUSTOMER SPECIFICATION GEOPHONE MODEL HS 1 LT DESCRIPTION ORIENTATION NATURAL FREQUENCY F TILT ANGLE MEASURED FROM Horizontal FREQUENCY SHIFT AT TILT ANGLE FREQUENCY TOLERANCE WITH TILT CLEAN BAND PASS SPURIOUS RESPONSE DC RESISTANCE 25 R INTRINSIC VOLTAGE SENSITIVITY G NORMALIZED TRANSDUCTION CONSTANT Coil Resistance R 1240 OPEN CIRCUIT DAMPING MOVING MASS M COIL EXCURSION P P HARMONIC DISTORTION Hz WITH DRIVING VELOCITY OF 7 in sec 1 8 cm sec DAMPING CONSTANT B R OPERATING AND STORAGE TEMPERATURE MAXIMUM OPERATING TEMPERATURE DIMENSIONS
75. States Department of Transportation The ITI Research Engineering Group Daniel R Marron David E Kosnik and the late Daniel J Hogan have been my closest partners during my time at Northwestern From these three gentlemen I have learned more than from any classroom teacher We have travelled the country together from the Everglades to the Pacific Northwest at every destination encountering unique challenges and meeting them as a team From Mr Hogan I learned that befriending a man with a welder can solve more problems than you might think especially when you need to drop the anchor From Mr Marron I learned that any engineering task is possible if you re near enough to a hardware store From Mr Kosnik I learned that I can be as fascinated by a coincidental juxtaposition of municipal and private water towers as by staring upward from inside the construction site at the World Trade Center These and other life lessons learned while part of the Research Engineering Group will stay with me for the rest of my engineering career Without the contributions of undergraduate research assistant Ken Fuller the experiments in Chapter 4 would have been impossible Mr Fuller assisted me by completing almost all of the preparation of the test coupons accompanying me to the industrial paint warehouse and making himself available for long hours in the mechanical testing lab His reliability work ethic attention to detail and camaraderie were invaluabl
76. The information and recommendations set forth in this Product Data Sheet are based upon tests conducted by or on behalf of The Sherwin Williams Company Such information and recommendations set forth herein are subject to change and pertain to the product offered at the time of publication Consult your Sherwin Williams representative to obtain the most recent Product Data Information and Application Bulletin SURFACE PREPARATION Surface must be clean dry and in sound condition Remove all oil dust grease dirt loose rust and other foreign material to ensure adequate adhesion Refer to product Application Bulletin for detailed surface preparation in formation Minimum recommended surface preparation Iron amp Steel Atmospheric SSPC SP2 3 Immersion SSPC SP10 NACE 2 2 3 mil 50 75 micron profile Aluminum SSPC SP1 Galvanizing SSPC SP1 Concrete amp Masonry Atmospheric SSPC SP13 NACE 6 or ICRI 03732 CSP 1 3 Immersion SSPC SP13 NACE 6 4 3 1 or 4 3 2 or ICRI 03732 CSP 1 3 Surface Preparation Standards Condition of 150 8501 1 Swedish Std Surface BS7079 A1 SIS055900 SSPC NACE White Metal 5 SP5 1 Near White Metal 25 Sa 2 5 SP10 2 Commercial Blast Sa2 Sa SP6 3 Paz El Hand Tool Cleaning Bild Rusted 812 555 Power Tool Cleaning Pitted amp Rusted D St 3 BSt3 SP3 TINTING Tint Part A with Maxitoners at 150 strength Five minutes minimum mix ing on a mechanical shake
77. ality of the newly invented hardware first discussed in Chapter 3 Appendix B contains manufacturer data and specification sheets for the commercially avail able sensors wireless sensor networks batteries and electronics mentioned throughout the thesis A separate document Wireless Sensor Networks for Monitoring Cracks in Structures Source Code and Configuration Files Kotowsky 2010 contains all of the source code and configu ration files used to implement the various systems described in the thesis Only code that was modified from the original manufacturer code is included 2 Fundamentals of the Monitoring of Cracks 2 1 Overview of Autonomous Crack Monitoring Autonomous Crack Monitoring ACM systems grew out of increasing public concern that construction and mining activities cause structural damage to nearby residences in the form of cracking of interior wall finishes ACM systems can satisfy the need of mine operators construction managers homeowners and their lawyers to quantify exactly how much if any damage the vibration inducing activity causes to a residence The purpose of ACM systems first described in Siebert 2000 as Autonomous Crack Com parometers is to compare the effects of long term weather induced changes in crack width with changes induced by nearby construction activity blasting activity wind gusts thunder claps or common household activity and publish this comparison to a Web site for
78. also functional but prematurely de bonded from the steel and ceased to function as the experiment progressed Two custom gages were drawn on a painted coupon at room temperature and performed as designed Since elevated temperature curing conditions are difficult to achieve on an in service high way bridge and since the propagation direction of a crack and therefore the proper orientation in which to install a pre manufactured gage may not be known at the time of installation the paint on gage is more practical for field use than either of the pre manufactured gages 5 2 Future Work 5 2 1 Wireless Autonomous Crack Monitoring Autonomous Crack Monitoring will continue to be a useful technique in litigation and regula tion of the mining and construction industries reductions in cost installation time and intru siveness made possible by implementing ACM using a WSN will only make the technique more useful The MICA2 platform is now several years old and is not a focus of active hard ware development therefore future wireless ACM work should be implemented on a different WSN platform such as the Microstrain V Link the Crossbow Imote or the Moteware Irene platforms The Shake n Wake design can be modified to work with any WSN platform that allows for direct physical and software access to the processor s interrupt lines 112 5 2 2 Wireless Autonomous Crack Propagation Sensing Autonomous Crack Propagation Sensing has been prov
79. and basic drivers A variety of useful applications and development tools are also provided Processor Board Daughter Card 3 50 37 1955 E Qu 020 j la 2135 2 49 T 2 290 E oo 020 _ 340 Le E 1800 __ 10 1800 10 330 200 408 965 3300 408 324 4840 E mail fo xbow com The Stargate processor module is compatible with Crossbow s IRIS MICAZ MICA2 family of wireless sensor networking products and the public domain software from Intel s Open Source Robotics initiative The Stargate processor module is also an ideal solution for standalone Linux based Single Board Computer SBC applications With its strong communications capability and Crossbow s ongoing commitment to its open source archi tecture the Stargate platform offers tremendous flexibility The SPB400CB Processor Board has both Compact Flash and PCMCIA connectors as well as optional installable headers for 2 serial ports and an I2C port The SDC400CA Daughter Card supports a variety of additional interfaces including RS 232 Serial 10 100 Ethernet USB Host Finally the standard Mote connector on the SPB400CB Processor Board provides support for synchronous serial port SSP UART and other GPIO connec
80. arameters Data 5 6 7 8 Stop Bits 1 1 5 2 Parity None Even Odd Space Mark Flow Control RTS CTS XON XOFF ADDC automatic data direction control for RS 485 Baudrate 50 bps to 921 6 Kbps supports non standard baudrates see user s manual for details Serial Signals RS 232 TxD RxD DTR DSR RTS CTS DCD GND RS 422 TxD TxD RxD RxD GND RS 485 4w TxD TxD RxD RxD GND RS 485 2w Data Data GND LEDs System OS Ready Console TxD RxD LAN 10M 100M x 2 Serial TxD x 8 RxD x 8 UC 7408 7410 7420 UC 7408 7410 7420 Plus only Physical Characteristics Housing SECC sheet metal 1 mm Weight UC 7410 810 g UC 7420 875 g Dimensions 197 x 44 x 125 mm 7 76 x 1 73 x 4 92 in Mounting DIN Rail wall Environmental Limits Operating Temperature 10 to 60 C 14 to 14096 Operating Humidity 5 to 95 RH Storage Temperature 20 to 80 C 4 to 176 F Anti vibration 1 g IEC 68 2 6 sine wave resonance search 5 500 Hz 1 Oct min 1 cycle 13 min 17 sec per axis Anti Shock 5 g IEC 68 2 27 half sine wave 30 ms Power Requirements Input Voltage 12 to 48 Power Consumption UC 7410 10 W 415 24 VDC 830 mA 12 VDC UC 7420 11 W 450 mA 24 VDC 890 mA 12 VDC Regulatory Approvals EMC CE EN55022 Class A EN61000 3 2 Class A EN61000 3 3 EN55024 FCC Part 15 Subpart B CISPR 22 Class A Safety UL cUL UL60950 1 CSA C22
81. ateway IRIS MICAz MICA2 Connectivity die MIB510 with Mote and Sensor Board Serial Port MIB510 Block Diagram Phone 408 965 3300 Fax 408 324 4840 Crossb w 510 MIB510 allows for the aggrega tion of sensor network data on a PC as well as other standard computer platforms Any IRIS MICAz MICA2 node can function as a base station when mated to the MIB510 serial interface board In addition to data transfer the MIB510 also provides an RS 232 serial programming interface The MIB510 has an onboard processor that programs the Mote processor radio boards The proces sor also monitors the MIB510 power voltage and disables programming if the voltage is not within the required limits Two 51 pin Hirose connectors are available allowing sensor boards to be attached for monitoring or code development The MIB510 is also compatible with the Atmel JTAG pod for code development Specifications RS 232 Interface Connector 9 pin D Baud Rates User defined 57 6k typical Programming 115 2k uisp controlled Mote Interface Connectors 51 pin 2 Indicators Mote LEDs Red Green Yellow Programming Interface Indicators LEDs Power Ok Green Programming in Progress Red Switches On Off switch to disable the Mote serial transmission Temporary switch to reset the programming processor and Mot
82. attributed to the hysteresis of the comparator described in detail in the comparator s product data sheet in Maxim Integrated Products 2003 In order to accurately determine the threshold voltage the Shake n Wake must be calibrated by the user with the desired sensor over the range of desired input frequencies Though Figures A 4 and A 5 do indicate that though the trigger threshold varies with frequency it is predictable in each pe riod of the input waveform the trigger occurs at approximately the same input voltage This 123 satisfies the requirement that the trigger threshold be both predictable and repeatable though sensor and frequency specific calibration is required for precise predictions Trigger threshold vs motion frequency 20 T T T T ae e 4 2 Ne D gt X E t 8 x 5 T 2 E E 4 5 12 5 T a 8 10 4 5 GS 14 measured gt gt HS 1 Geophone measured i Theoretical Trigger Level X 5 10 15 20 motion frequency Hz Figure A 6 Summary of Shake n Wake level 2 trigger threshold voltages A 2 1 Physical Meaning of Trigger Threshold The HS 1 and the GS 14 geophones each have a different characteristic response to vibration phenomena These responses are shown graphically in Appendices B 8 and B 9 respectively Figure A 7 shows the trigger levels derived from the springboard expe
83. break It is important to note that the predicted behavior of the voltage output as the rungs break is non linear This is like in the case of the narrow gage in Section 4 2 2 due to the fact that equivalent resistance of resistors in parallel is equal to the reciprocal of the sum of the reciprocals of all of the resistors values Calculated Output of Custom Gage 2 8 2 6 j 22 Sensor Reading 1 1 1 1 1 li ji 0 1 2 3 4 3 6 7 8 9 Rungs Broken Figure 4 18 Predicted change in output voltage of custom crack propagation sensor with rungs broken 103 The rungs of the crack propagation gage can be any conductive material For the sensor prototype a CircuitWorks Conductive Pen the full technical details of which can be found in Appendix B 12 was used to connect the individual rungs on the two sides of the custom crack propagation sensor The pen draws a highly conductive silver trace which sets and cures in approximately thirty minutes CHEMTRONICS 2009 While the commercially manufactured crack propagation patterns in Section 4 2 2 were designed to be glued to bare steel the custom crack propagation gages must be affixed to a non conductive material for proper functionality In a field deployment of this sensor which would likely be on an in service steel highway bridge the existing bridge paint system would insulate the conductive
84. ccurs because each rung of the wide gage has a resistance specifically de signed such that when it is broken the change in the overall resistance of the sensor is linear not exponential The narrow gage s rungs are all approximately the same width and therefore have the same resistance This behavior becomes significant when signal resolution is considered in Section 4 2 1 a b Figure 4 5 Crack propagation patterns a TK 09 CPA02 005 DP narrow b 09 003 DP wide 4 2 1 Integration with Environmental Sensor Bus The Pro Series WSN is designed to be used with sensors that communicate over Cross bow s Environmental Sensor Bus ESB The ESB protocol Crossbow Technology Inc 2009c 90 5 5 gt 45 Direction of P Propagation 40 p 1 2 Size 30 25 RESISTANCE OHMS WITH 50Q SHUNT RESISTANCE OHMS WITH 500 SHUNT N 0 0 0 5 10 15 20 0 5 10 15 20 STRANDS FRACTURED STRANDS FRACTURED CPA01 amp 2 b Figure 4 6 Crack propagation resistance versus rungs broken for a TK 09 CPA02 005 DP narrow b TK 09 CPC03 003 DP wide after Vishay Intertechnology Inc 2008 describes a specific connector type power supply and digital interface scheme that must be im plemented by the
85. d PC interface or gateway board The MIB510 MIB520 provides a serial USB interface for both programming and data communications Crossbow also offers a stand alone gateway solution the MIB600 for TCP IP based Ethernet networks MIB520 Mote Interface Board Ordering Information Model Descripti WSN START900CA MICA2 Starter Kit 868 916 MHz WSN PROS00CA MICA2 Professional Kit 868 916 MHz MPR400CB 868 916 MHz Processor Radio Board Document Part Number 6020 0042 08 Rev A Crossbow Technology Inc 4145 North First Street San Jose California 95134 2109 134 B 2 String Potentiometer Data Sheet Data Sheet Series 150 Subminiature Position Transducer Firstmark Providing the Ultimate Solutions in Precision Displacement Sensors http www firstmarkcontrols cony s021f htm Order Site Map All Products Support Special Offers Contact Us Data Sheet Series 150 Subminiature Position Transducer World s Smallest Cable Position Transducer Shaded characteristics are verified during production and test All others are for REFERENCE and information Key Features only 1 5 Inch 38 mm Maximum Travel Analog Signal Using Precision Conductive Plastic Potentiometer AccuTrak Grooved Drum for Enhanced Repeatability 1 Small Robust Design Choice of Displacement Cable Pull Direction DirectConnect Sensor To Drum Technology Zero Backlash No Torsion Springs or Clutches
86. d be instructed to start and stop logging change sampling rate and transmit data A single MICA2 mote was programmed with application TOSBase an application provided by the manufacturer and used without modification and inserted into the MIB510CA base station Instead of connecting the base station directly to a PC the base station was connected to a serial to Internet Protocol gateway that was then attached to the test house resident s consumer grade cable modem Using that gateway a PC in the lab could issue commands directly to each mote over the Internet Once the motes were installed and the Internet connection established the user would sim ply use the PC to connect to each mote and instruct it to begin logging at an arbitrary interval e g once per hour To conserve power the MDA300Logger application would instruct the mote to shut down five minutes after it completed taking its data readings This five minute period of full power would give the remote user a window in which he could retrieve a mote s data change a mote s sampling interval or command the mote to stop logging The user had to 42 maintain a careful record of when each mote was started and stopped such that it would known exactly when the motes would be powered on and available to respond to commands An additional piece of software the XSensorMDA300 software package included with the development kit was used to center the string potentiometer An extra MICA2
87. d themselves well to ACPS five month battery lifetime integrated solar panels to extend the battery lifetime to five years a simple web based interface that requires no programming by the user and rugged outdoor rated hous ing Though no sensors have been manufactured to allow the system to perform ACPS monitoring its implementation of the Environmental Sensor Bus ESB allows a third party sensor manufacturer can create a custom interface such that a sensor may be used with any eKo mote Chapter 4 described two types of crack propagation sensors that were made compatible with the ESB and made to function with the motes The first type commercially manufactured resistive crack patterns are designed to be glued directly to steel in which a crack has formed The second type a custom crack propagation gage is designed to be drawn on to a painted section of steel in which a crack has formed 111 Chapter 4 described a series of experiments in which both types of commercially available sensors were integrated with ESB circuitry and attached to steel compact tension specimens The pre manufactured test coupons were functional and performed as designed when affixed to the coupons using elevated temperature curing adhesive but the first several rung breaks of the narrow gage were not recorded by the mote due to their small voltage changes The gages attached to the coupon with room temperature curing adhesive were
88. d uncrimped Nominal Mass 0 5 oz 15 0 g Displacement Cable Tension and Cable Acceleration Nominal Opt 1 1 oz 0 3 N min 6 oz 1 7 N max 29 g max Displacement Cable Tension and Cable Acceleration Nominal Opt 2 3oz 0 8N min 14 oz 3 9 N max 49 g max Environmental Protection IE1E1 ABXHXFDXSAXXXXXXXXXX NEMA 35 IP 54 DO 160D ED 14D Env Cat Model Numbers and Ordering Codes 150 0121 abc position transducer 1 50 inch 38 mm range Example 150 0121 L2N left hand displacement cable pull cable tension 020 no base Variable Value Description L left hand displacement cable pull 3 R right hand displacement cable pull b 1 cable tension 010 2 cable tension 020 N no base e B base L pn 150015 Drawing 135 136 Data Sheet Series 150 Subminiature Position Transducer 57 14 5 2X 2 56 UNC THREADED MNTG HOLES SCREW REMOVED FOR CLARITY PROVIDED WITH FLAT WASHERS AND 2 56 UNC x 1 4 INCH SOCKET HEAD CAP SCREW 5 64 SOCKET http www firstmarkcontrols com s021 f htm LEFT HAND PULL _ DISPLACEMENT CABLE 38 RIGHT HAND PULL DISPLACEMENT CABLE 20 6 1 A 1 52 3 05 060 120 ELECTRICAL CABLE 3 CNDCT FLYING LEAD 30 GAUGE MIN 18 IN 457 MM MIN LENGTH Electrical Connection for Increasing Output with Displacement Cable Extraction Left Hand Pull Right Hand Pul
89. ded for immersion service Use only Mil White and Black for immersion service Insufficient ventilation incomplete mixing miscatalyzation and external heaters may cause premature yellowing Excessive film build poor ventilation and cool temperatures may cause solvent entrapment and premature coating failure Quik Kick Epoxy Accelerator is acceptable for use See data page 4 99 for details Refer to Product Information sheet for additional performance characteristics and properties SAFETY PRECAUTIONS Refer to the MSDS sheet before use Published technical data and instructions are subject to change without notice Contact your Sherwin Williams representative for additional technical data and instructions DISCLAIMER The information and recommendations set forth in this Product Data Sheet are based upon tests conducted by or on behalf of The Sherwin Williams Company Such information and recommendations set forth herein are subject to change and pertain to the product offered at the time of publication Consult your Sherwin Williams representative to obtain the most recent Product Data Information and Application Bulletin WARRANTY The Sherwin Williams Company warrants our products to be free of manufacturing defects in accord with applicable Sherwin Williams quality control procedures Liability for products proven defective if any is limited to replacement of the de fective product or the refund of the
90. derstood but thought to be an issue with the mesh networking protocol Figure 3 31d shows that Mote 4 used Mote 3 as an intermediary which was the only difference between those motes 74 d Figure 3 30 Version 3 wireless ACM nodes located a on the underside of the service stairs b over service stair doorway to kitchen and c on the wall of the main stairway d the base station in the basement Diagnostic logs on the base station showed that Motes 1 and 2 the motes underneath the service staircase with no MDA300CA sensor boards did not reply when the sampling interval workaround was implemented near day 75 The most reasonable explanation for this behavior is that the lack of MDA300CA attached to these motes caused the XMesh power management algorithm to fail causing the batteries to deplete after only two days approximately the same expected lifetime of a MICA2 with no power management Figure 3 31d does show that Mote 1 was functioning as a parent mote for Mote 3 before it failed 75 Temperature vs Days Deployed Humidity vs Days Deployed pe ys Deploy ty vs Days Deploy 30 70 Mote 3 Mote 3 Mote 4 Mote 4 LR M 60 h MI 52 8 3 Ii V Ej IN B E m dr E B ud MER aist Mi
91. dicates that the mote has executed its first line of user code In a real event detection system this first post wakeup instruction would be to immediately begin sampling at a high frequency The power draw of entire system shown in pink begins to increase from its sleep level as soon as the Shake n Wake sends its wakeup signal This timing diagram shows that the interval between the moment the input signal reaches the theoretical trigger threshold and the moment the Shake n Wake signals a wakeup is 58 us and the time interval between when the Shake 7 Wake signals a wakeup and the time the first line of user code is executed on the mote is 31 us Since this 89 us is well within the specified 11 5 millisecond window it follows that the Shake Wake can perform within the timing requirements A 4 Discussion These experiments have served to quantify the abilities of the Shake n Wake hardware rela tive to the requirements of a random event detection scenario The suitability of the geophones is limited on one end by amplitude if the vibration frequency is not high enough the required output amplitude for the Shake n Wake to trigger at its most sensitive setting becomes unreach able On the other end of the frequency range the limit of functionality is the response speed of the Shake Wake hardware Table A 1 summarizes the practical limits of the Shake n Wake with respect to frequency of geophone output 128
92. e Jtag Interface Connector 10 pin male header 2 Power 5V 50mA using external power supply included with unit 3 3 2 7V 50mA using Mote batteries Ordering Information Model 510 Description Serial PC Interface Board E mail info xbow com Document Part Number 6020 0057 03 Rev A Web www xbow com B 5 Stargate Data Sheet STARGATE X SCALE PROCESSOR PLATFORM 400 MHz Intel PXA255 Processor Low Power Consumption 500 mA Embedded Linux BSP Package Source Code Shipped with Kit Small 3 5 x 2 5 Form Factor PCMCIA and Compact Flash Connector 51 pin Expansion Connector for IRIS MICAz MICA2 Motes and other Peripherals Ethernet Serial JTAG USB Connectors via 51 pin Daughter Card Interface Li lon Battery Option Applications Sensor Network Gateway Robotics Controller Card Distributed Computing Platform 139 Crossb w STARGATE The Stargate is a high performance processing platform designed for sensor signal processing control and wireless sensor networking applica tions and is based on Intel s Xscale processor The Stargate processor board is the result of the combined design efforts of several different Ubiquitous Com puting research groups within Intel The completed design is licensed to Crossbow Technology for commercial production The Stargate processor board is preloaded with a Linux distri bution
93. e 2 Version 2 Mote 3 Version 2 Mote 4 2 E E ba EE Miet a wl T 3000 fi 2800 3400 di Prset id 3200 f Battery mV 2600 4 2400 1 2200 4 2000 0 50 100 150 200 250 300 Days Deployed Figure 3 33 Comparison of battery voltage versus time for the Version 2 and Version 3 wireless ACM systems Figure 3 32c shows that the MDA300CA reported what appear to be three different sets of string potentiometer readings each separated by an approximately 1800 pseudo constant offset In post processing it is possible to filter the three sets of data into three regions as shown in Figure 3 34 under the assumption that each region represents the same physical reading with constant 1800 offsets 84 of the data points fall into the region with an absolute value above 760 The high region as outlined Table 3 3 contains the majority of the recorded 78 points Figure 3 35 shows plots of temperature and humidity versus the high region of measured crack width Mote 3 Crack Expansion vs Days Deployed filtered 3000 2000 1000 1000 Crack Expansion microinches 2000 3000 4000 80 90 100 110 120 130 Days Deployed Figure 3 34 Plot of three separate sets of crack width data as recorded by Mote 3 of the Ver sion 3 wireless ACM system Points R
94. e formation of the mesh network and change the triggering threshold of the Shake n Wake devices xlisten the application that allows a PC to read data coming back from the network was modified to understand threshold crossing messages and messages acknowledging receipt of commands This modified software can be found in the separate publication Kotowsky 2010 69 Implementation of Version 3 also required modification of the software that runs on each MICA2 This modification activates an interrupt request channel on the MICA2 and instructs the mote to send back a trigger received message upon activation of that interrupt The mote will also send back its most recent data readings from the MDA300CA upon receiving a Shake Wake trigger Additionally the on mote code was modified to accept the receiving of and responding to commands from a PC This modified software can be found the separate publication Kotowsky 2010 3 3 7 2 Operation The addition of the ability to send commands to the sensor network from the base station sub stantially changes the installation procedure after the mote and sensors have been attached to the structure Rather than using a physically separate calibration mote to center the string poten tiometer an engineer can center the potentiometer using only the Version 3 software Once the motes are powered on the engineer can connects to the base station using any 802 11 capable PC He logs into the UC 7420
95. e to me Melissa Mattenson an old friend and more recently my next door neighbor at the office contributed vastly to my graduate work with a steady stream of gummy stars needless or were they lunch trips to the best Evanston eateries and moral support mere steps from my desk For longer than near decade I have been associated with ITI Autonomous Crack Monitoring ACM has been a research focus of the Institute The published work of several students some of whom I have never met has been essential to the research presented in this thesis I would especially like to thank three of these former students for their individual roles in ACM project Damien R Siebert received his M S in 2000 after publishing his thesis Autonomous Crack Comparometer five months before I first began work at ITI His work heavily referenced in this document provided the basic principles on which I based my research Hasan Ozer who received his M S in 2005 was my partner in ITI s first exploration of wireless sensor networks Mr Ozer and I with our respective undergraduate backgrounds in civil and computer engineering found ourselves learning together and teaching each other how to make wireless sensor networks work for us He was my partner in the project that received third place honors at the Second Annual TinyOS Technology Exchange in 2005 and his contributions to wireless ACM have been invaluable Jeffrey E Meissner research assistant to Profe
96. ecorded Percentage Bounds mV Bounds High 4634 84 gt 1 9mV gt 760 uin Mid 736 13 1 9mV gt gt 2mV 760 uin gt gt 800 uin Low 160 3 lt 2mV lt 800 uin Table 3 3 Results of filtering Version 3 wireless ACM potentiometer readings 79 Mote 3 Crack Expansion and Humidity vs Days Deployed 2200 T T T T 55 Humidity Crack Expansion 2000 J 50 BUM yox ow 1800 pO A i S i em 8 1600 V 5 2 5 5 1400 5 5 3 135 B m 1200F i 9 4 1000 800 15 600 1 1 1 L L L L 20 80 90 100 110 120 130 140 150 Days Deployed a Mote 3 Crack Expansion and Temperature vs Days Deployed 2200 T T T T T 24 Temperature Crack Expansion 4 22 2000 1 ory L 4 20 1800 ui T i 4 18 E 1600 2 8 416 9 2 B 3 o 5 1400 414 B 2 5 E E 1200 5 4 10 1000 I Js 800 600 1 1 1 1 1 1 1 4 80 90 100 110 120 130 140 150 Days Deployed b Figure 3 35 Plots of a humidity and b temperature versus filtered crack displacement recorded by the Version 3 wireless ACM system over the 75 day period of in terest 80 3 3 8 Wireless ACM Conclusions This chapter has described three versions of a wireless ACM system built on the MICA2 plat form Version 1 was a
97. ed on a bridge e ACPS using a wireless sensor network may not require special software or program ming skills 87 4 1 3 The Wireless Sensor Network The Pro Series Wireless Sensor Network WSN shown in Figure 4 3 commercially pro duced by Crossbow Technology Inc is specifically designed for environmental and agricultural monitoring Each Ko mote is water and dust resistant capable of operating in wide tempera ture and humidity ranges and will operate for over five years with sufficient sunlight Crossbow Technology Inc 2009a The base station which must be connected to 110 V AC power and a network connection can transmit e mail alerts when sensor readings cross programmable thresholds The eKo WSN s robust design makes it an attractive platform for deployment in the harsh operating environment of an in service highway bridge It is equally important to note that an mote end user need not manually program the system to function properly which is attractive to bridge engineers The eKo motes record data every thirty seconds for the first hour after activation Thereafter they record once every fifteen minutes a b Figure 4 3 a eKo Pro Series WSN including base station after Crossbow Technology Inc 20092 b Individual eKo mote with a 12 inch ruler for scale 88 4 2 ACPS Using Commercially Available Sensors Direct measurement of the elongation of a crack can be measured with a c
98. ederal Highway Administration 2006 86 The tracking of crack growth by visual inspection has several drawbacks the most obvious of which is that documentation of the conditions of cracks can only be updated during inspec tions which may occur as infrequently as once every two years Less obviously photographic records of crack length tend not to be repeatable due to changes in photography angle ambient light photographic equipment and inspector 4 1 2 Other Crack Propagation Detection Techniques Several other techniques exist for the detection classification and monitoring of fatigue crack ing in structures Acoustic emission monitoring as described in Hopwood and Prine 1987 can be used to determine whether a crack is actively growing or has extinguished itself Stolze et al 2009 describe a method to detect and monitor the progression of cracks using guided waves ACPS with wireless sensor networks has several distinct advantages over these structural health monitoring techniques when applied to in service bridges e ACPS is designed to be deployed for months or years on an actively utilized structure The other techniques are not designed to be used in the field for more than a few days e ACPS using commercially available wireless sensor networks is an order of magnitude less expensive than acoustic emission or guided wave equipment e ACPS sensors on a wireless network do not require power or signal cables to be in stall
99. en in the lab and now must be qualified in the field The custom crack propagation patterns must be tested for overall field durability over long periods of time Additional experiments may be necessary to determine the best method of physical protection of the circuitry and the painted traces of the custom crack propagation gage 113 References Baillot R 2004 Crack response of a historic structure to weather effects and construction vibrations Master s thesis Northwestern University Evanston Illinois Bourns I 2006 4600X Series Thick Film Conformal SIPs Crossbow Technology Inc 20073 MDA300CA Data Acquisition Board http www xbow com Products Product_pdf_files Wireless_pdf MDA300CA Datasheet pdf Crossbow Technology Inc 2007b MPR MIB Users Manual http www xbow com u upport Support pdf files MPR MIB Series Users Manual pdf Crossbow Technology Inc 2007c MTS MDA Sensor Board Users Manual http www xbow com Support Support pdf files MTS MDA Series Users Manual paf Crossbow Technology Inc 2007d Stargate Gateway http www xbow com Products Product_pdf_files Wireless_pdf Stargate_Datasheet pdf Crossbow Technology Inc 2007e XMesh Users Manual http www xbow com Support Support pdf files XMesh Users Manual pdf Crossbow Technology Inc 2009a ko pro series data sheet http www xbow com eko pdf eKo pro series Datasheet pdf Crossbow
100. er measuring the expansion and contraction of a plastic donut 54 3 3 5 5 Results Version 2 of the MICA2 based wireless ACM system was deployed in the test structure from March 2006 through November 2006 Figure 3 16 shows a plot of the voltage of the batteries versus days of deployment Mote 2 the mote deployed in the basement depleted its batteries the most quickly after approximately 140 days of deployment Mote 4 the mote deployed on the sun porch fared next best with a lifetime of approximately 210 days After approximately 250 days when the system was removed from the test structure neither Mote 1 nor Mote 3 had depleted its batteries Battery vs Days Deployed 3600 3400 3200 3000 Battery mV 2800 2600 4 2400 4 50 100 150 200 250 300 Days Deployed Figure 3 16 Plot of each mote s battery voltage versus time 55 Figure 3 17 compares the expansion and contraction of the donut with the ambient tempera ture The mote with the donut was placed on the sun porch which was minimally insulated and had no climate control Figures 3 18 and 3 19 compare the ambient temperature and humidity respectively recorded by each mote over the deployment period Motes and 4 were deployed in environments highly influenced by outdoor temperature Motes 2 and 3 were deployed in climate controlled indoor spaces Along with the battery temperature humidity and potentiometer readin
101. ery hour the system will measure ambient indoor and outdoor temperature ambient indoor and outdoor humidity and the current widths of all cracks Though ideally only one sample per sensor per hour is necessary to observe these long term effects it is often common practice to measure average short bursts of high frequency measurements e g sample one thousand samples for one second and average to attempt to filter out any noise or electromagnetic interference that may be introduced due to long cable runs This long term periodic measurement of temperature humidity and crack sensors is known as Mode 1 logging and is the simpler of the two modes in which an ACM system operates It should be noted that readings from geophones are ignored in Mode 1 logging because slow periodic readings from a geophone yield no useful physical information 2 4 1 2 ACM Mode 2 Dynamic Physical phenomenon other than temperature and humidity can have effects on cracks in the walls of structures the very motivation behind the development of ACM systems is to char acterize the effects of construction vibration and blasting on houses These types of events have two characteristics that make them ill suited for recording in Mode 1 First they can occur at any time one cannot assume that even the most organized construction or mining 18 operation will have a precise enough schedule of their daily activities that a system can be programmed to record at
102. es This thesis describes the use of Wireless Sensor Networks WSNs to greatly reduce the cost and installation effort of these systems and to make practical their use in situations where the use of wired versions would be impossible ACM is a structural health monitoring technique that measures and records the changes in widths of cracks and time correlates these changes to causal phenomena in and around the struc ture autonomously making available the data and analyses via a securely accessible Web page Developed as a tool to support regulation and litigation in quarrying mining and construction an ACM system is typically installed for a period of months or years in a residential structure during which time it records continuously and publishes autonomously to the Web changes in the widths of cosmetic cracks in walls ambient environmental conditions ground vibrations air overpressure and internal household activity This data is then used to determine the effect of the blasting or other vibratory activity on cyclical widening and narrowing of cosmetic cracks ACPS is a structural health monitoring technique that measures and records the propagation of existing cracks in structures not only automatically making available the data via a securely accessible Web page but also alerting stakeholders via e mail telephone text message or pager should cracks extend beyond some pre determined length Developed for use on steel bridges ACPS is d
103. esigned to supplement federally mandated crack inspection procedures which suffer from poor repeatability and low frequency of occurrence with precise objective and repeatable information on the condition of cracks This thesis will discuss the challenges of advancing of long term structural health monitor ing systems from the wired to the wireless domain It will describe the design development and deployment of three iterations of a wireless ACM system built on a commercially avail able wireless sensor network WSN platform and examine three case studies in which wireless ACM systems were installed in residential structures It will then discuss the design of an ACPS system based on both commercially available and custom designed sensors and detail laboratory proof of concept experiments to demonstrate the system Chapter 2 describes the fundamentals of the monitoring of cracks It will discuss the motiva tion for ACM and ACPS describe exactly what physical phenomena they measure and provide an example of the output of a traditional wired ACM system It will consider the various types of sensors and address their suitability for monitoring cracks using both wired and wireless sys tems Finally Chapter 2 will discuss the different recording modes used by crack monitoring systems These modes specify sampling rates and conditions that must be implemented by the data logger on which the monitoring system is built The monitoring systems uti
104. f each MDA300CA so that the entire mote could be affixed to the ceiling using hook and loop fastener as shown in Figure 3 7b instead of epoxy A nylon cable tie secured each MICA2 to the MDA300CA because the motes were not designed to be inverted and the 51 pin connector 39 could not support the weight of MICA2 and two AA batteries The string potentiometer and its cable clamp were affixed to the ceiling using the quick setting epoxy used by Siebert 2000 The MIB510CA with another MICA2 mote installed were located only a few feet away in a nearby closet and attached directly to the Internet via a commercially available serial to Internet Protocol gateway 40 b Figure 3 7 Photographs of Version 1 of the MICA2 based wireless ACM system after Ozer 2005 a base station in closet b node on ceiling monitoring crack 41 3 3 4 2 Software The application software written for Version 1 of the MICA2 based wireless ACM system was known as MDA300Logger The application itself and the utility applications and libraries re quired to make it operational are based on the example application SenseLightToLog included with the MICA2 development kit from Crossbow The separate publication Kotowsky 2010 contains all of the modified source code that was used to change SenseLightToLog 3 3 4 3 Operation The MDA300Logger application directed each mote onto which it was installed to act as an independent data logger that coul
105. f plane Figure 2 5 Different directions of crack response after Waldron 2006 Ease of installation and removal also plays a role in sensor selection the crack sensor must be rigidly i e with minimal creep due to gravity and robustly i e able to last for the entire duration of the monitoring activity attached to the wall at the location of a crack This dictates 12 the use of quick setting epoxy as described in Siebert 2000 The larger the area that needs to be glued the more difficult and destructive sensor removal will be Design of a wired ACM system typically does not need to take into account the power draw of a given sensor type the system has a power source typically household 110 V AC service so large that power considerations are usually ignored in sensor selection In a wireless system however power is a much greater concern as discussed in Chapter 3 and Chapter 4 Table 2 1 shows the various factors to consider when selecting a sensor for an ACM system LVDT Eddy Current Potentiometer Model DC 750 050 SMU 9000 Series 150 Approximate Cost 250 1700 400 Measuring Range 0 05 in 0 05 in 1 5 in Out of plane capable no yes minimally Physically bridges crack yes no yes Footprint large small small Power Requirements 15 V DC 25mA 7 15 DC 15 mA 7mAat35 V DC Warm up time 2 minutes 30 minutes none The string potentiometer is not designed to measure motions in d
106. frastructure Technology Institute ITI This unusual employment ar rangement blossomed into a summer internship at ITI employment after graduation and even tually entrance into graduate school Instead of moving to California to write software for a large company in Silicon Valley I have spent the last several years of my life travelling the country and applying my computer and civil engineering education to exciting instrumentation projects Professor Corr only recently joined the ITI team but his industry experience and expertise in structural engineering immediately strengthened my work at ITI and gave me a fresh per spective on all of my efforts Both in the classroom and in the field Professor Corr reinforced my understanding of structural engineering concepts that were newer to me than to my class mates and gave me the confidence to go forward with my experiments in custom designed crack propagation sensors The late Professor David F Schulz founding director of ITI brought together a team of engineers that have turned my college job into a viable career path Professor Schulz and current ITI Director Joseph L Schofer have made available to me a world of engineering ex periences that I could not have imagined as an undergraduate To these gentlemen I am deeply iv indebted Nearly all of the research described in this thesis was funded by ITI via its grant from the Research and Innovative Technology Administration of the United
107. gh Drain Performance 50mA Continuous 21 C 1000mA Continuous 21 C AA Lithium Alkaline AA Lithium AA Alkaline 1 6 1 6 14 14 o g 1 2 5 12 5 5 S10 810 S S gt o8 gt 0 15 30 45 60 75 0 0 0 5 1 0 1 5 2 0 2 5 3 0 Service hours Service hours Constant Power Performance Constant Current Performance Typical Characteristics to 1 0 Volts 21 C Typical Characteristics to 1 0 Volts 21 C AA Lithium AA Lithium 1000 v 5 100 2 o 9 5 10 5 o 1 10 100 1000 10 100 1000 Discharge mW Discharge mA Application Tests 21 C Application Tests 21 C REMOTE RADIO CD GAMES DIGITAL AUDIO 24 ohm 15 sec min 8 hrs day 43 ohm 4 hrs day 250 mA 1 hr day 100 mA 1 hr day 16 1 6 8 14 B 14 12 12 8 10 REMOTE RADIO 5 CD GAMES TAPE PLAYER 10 0 8 0 8 0 20 40 60 80 100 0 7 14 21 28 35 Service hours Service hours Application Tests 21 C Industry Standard Tests 21 C TOOTHBRUSH PORTABLE LIGHTING TOY PHOTOFLASH DIGITAL CAMERA 500 mA 1 13 min 24 hrs day 3 3 ohm LIF 3 9 ohm 1 hr day 1K mA 10 sec min 1 hr day 1 5 65K mW 2 1 27 9s 10X 5 1 6 16 g 14 8 14 DIGITAL CAMERA 12 8 12 3 1 0 5 1 0 0 Tov oo PHOTO m 0 8 0 8 0 2 4 6 8 10 0 100 200 300 400 Service hours Service minutes Important Notice This datasheet contains typical information specific to products manufactured at the time of its publication GEnergizer Holdings Inc Contents herein do not constitu
108. great deal of his time to the often slow and laborious process of test setup Steve Albertson of Northwestern University s Department of Civil and Environmental Engi neering made himself and his lab available to me to do last minute mechanical testing when my intended machine suddenly broke down Without Mr Albertson s assistance the custom crack propagation gages described in Chapter 4 would not have been tested in time for the publication of this thesis This thesis was typeset using the nuthesis class for 2 developed by Miguel A Lerma of Northwestern s Department of Mathematics and amended by David E Kosnik of Northwestern University s Infrastructure Technology Institute To my parents Janet and Arnold Kotowsky and to my grandmother Anne Horwitz and my late grandfather Lawrence Horwitz I give thanks for their constant support through the times that I have struggled and instilling in me the work ethic and stubborn insistence on perfection that have come to define my attitude toward all my endeavors Finally to Kristen Pappacena who came into my life only a few short years ago I must give thanks for her inspirational example as she completed her Ph D in front of my eyes Her attitude and accomplishments served as an example for me as I worked toward my degree and her kind and caring ways have time and again seen me through the difficult times Table of Contents ABSTRACT Acknowledgements List of Tables List of
109. greater than 20 hertz be fore a 0 05 inch per second velocity can be detected by the Shake n Wake at level 2 However if the amplitude of motion is great enough the GS 14 can produce sufficient amplitude at low frequencies For the HS 1 geophone the frequency of motion can be as low as 2 hertz and still provide a large enough amplitude to trigger the Shake n Wake at level 2 no matter what the amplitude of the motion input velocity gt lips 0 05 GS 14 2 230H 20 23082 HS 1 2 2308 2 23082 Table A 1 Summary of functional ranges for Shake n Wake event detection at level 2 A 5 Appendix Conclusion The above experiments verify that the Shake n Wake e does not contaminate the sensor output e provides a predictable and repeatable threshold voltage e responds quickly enough to allow the mote to wake up in time to digitally record the signal of interest 130 can used with a GS 14 geophone to detect motions with a frequency 20 hertz and 230 hertz at amplitudes of 0 05 ips down to 2 hertz if amplitude is sufficiently large can be used with an HS 1 geophone to detect motions with a frequency between 2 hertz and 230 hertz regardless of amplitude 131 APPENDIX Data Sheets and Specifications The following pages contain specification and data sheets for all relevant commercially manu factured equipment described in this thesis All documents
110. gs it takes period ically each mote also sends back the identity of its parent mote in the XMesh routing tree at the time the data point is taken The first ACM packet i e a packet that contains sensor data rather than XMesh status data of the monitoring period came from Mote 2 at 12 00 AM on March 23 2006 Between that time and the time that the last data packet was received from Mote 2 the first mote to deplete its batteries at 11 42 PM on August 4 2006 37 268 ACM packets were received by the base station Of these packets 71 8 were received directly from the mote that recorded the data the packet hopped only once Mote 1 the mote in the garage sent most of its data back via either Mote 3 or Mote 4 however it transmitted 16 9 of its packets directly to the base station Table 3 1 shows the detailed listing of motes parents between the start of monitoring and the depletion of the first mote s batteries 3 3 5 6 Discussion Figure 3 17 indicates that Mote 4 recorded expansion and contraction of the plastic donut that correlated closely with temperature changes This demonstrates that the XMesh based ACM software can perform Mode 1 recording 56 Donut Expansion vs Temperature Seasonal Change 45 40 0 8 p Donut Temperature 4500 4000 sououro1orJA
111. he adhesive holding the gage to the steel coupon has released and allowed air to fill the gap between the coupon and the substrate of the crack propagation gage Once the brittle substrate of the gage separates from the surface on which it is mounted the gage will not only fail to reflect accurately the position of the crack tip beneath it but it will become extremely fragile and likely to fail due to some other physical phenomenon than crack propagation 4 3 Custom Crack Propagation Gage An implicit assumption made in the use of crack propagation gages such as those described in Section 4 2 2 is that the engineer has a priori knowledge at the time of sensor installation of 99 the direction in which the crack is going to propagate In cases where such knowledge does not exist several of these mass produced gages would be necessary to track the crack in all of its possible propagation directions Additionally the results of the experiment on Coupon C in Section 4 2 2 indicated that for the best results an impractical installation method involving elevated temperature cured adhesive must be employed to utilize these gages A solution to both of these problems is a so called custom crack propagation gage This type of gage is drawn rather than glued near the crack to be monitored using commercially available conductive material This material combined with a more sophisticated network of signal conditioning resistors creates a gage that
112. idation of Version 1 of the MICA2 based wireless ACM system the WSN manufacturer released to the public a set of software libraries XMesh designed to simplify power and network management of their WSNs WSN application software written using these software libraries automatically has the ability to create and maintain a self healing multi hop mesh network of motes The XMesh libraries also provide advanced power manage ment of the sensor network as a whole to maximize system longevity The manufacturer also supplied a sample application XMDA300 and a set of drivers for the to demonstrate its functionality This example software and the supplied hardware drivers were modified to implement Mode 1 recording Full source of all modified files can be 48 found in the separate publication Kotowsky 2010 It should be noted that the mote attached to the base station ran the same software as did all of the remote motes The XMDA300 software when installed on a mote with an identification number of zero will automatically function as a base station mote The original XMDA300 application was obtained from the manufacturer s publicly accessi ble Concurrent Versions System repository in April of 2005 The majority of the modifications took place in the main application control code XMDA300M nc as the general strategy of the application was changed As written the application would start the SamplerControl module part of the MDA300C
113. imized while ensuring that the current draw of the sensor never exceeds 8 mA the maximum current output of the mote s precision excitation voltage Table 4 1 shows for each possible combination of available bus resistor and current sense resistor the analog digital conversion steps for the first rung break Ohm s Law indicates that the fully intact resistance of the gage would need to be less than 3750 before the sensor would draw more than 8 mA at 3 V None of the resistor combinations listed in Table 4 1 can combine to form gage with an intact resistance of 3750 or less Bus Resistor Value 1 10KO 100KO 220KO 470 49 90 17 2 0 0 0 3 3740 29 14 2 1 0 5 1KQ 19 25 5 2 1 gluko 2 18 26 17 10 20KQ 1 11 30 24 16 49 9KQ 1 2 26 30 26 Table 4 1 Change ADC steps for first rung break for each combination of bus resistor and current sense resistor values 102 Table 4 1 shows that two resistor combinations yield the largest possible analog to digital step change for breakage of the first rung The larger resistor combination the 220 bus resistors and the 49 9 current sense resistor were chosen because the larger resistors will draw less current from the same voltage supply Full specifications of the 220 bus resistor can be found in Appendix B 11 Figure 4 18 shows the theoretical change in sensor output voltage as each of its nine rungs
114. ination of bus resistor and current sense resistor values 101 Summary of functional ranges for Shake n Wake event detection at level 2 129 XV List of Figures 2 1 Flow of data from sensors to users after Kosnik 2007 7 2 2 Sketch of a view of a crack to illustrate the difference between crack width and crack displacement change in crack width redrawn after Siebert 2000 7 2 3 Plan view of an ACM system installed in a residence after Waldron 2006 9 2 4 Photographs of three types of crack width sensors a LVDT after McKenna 2002 b eddy current sensor after Waldron 2006 c string potentiometer after Ozer 2005 10 2 5 Different directions of crack response after Waldron 2006 11 2 6 Photograph of a triaxial geophone with quarter for scale 13 2 7 Layout of miniature geophones such that wall strains can be measured after McKenna 2002 14 2 8 Photographs of a indoor and b outdoor temperature and humidity sensors after Waldron 2006 15 2 9 Resistance measured between points A and B decreases as crack propagates 20 2 10 Two types of commercially available crack propagation patterns shown with a quarter for scale 22 xvi 2 11 Screen shots of a long term correlation of crack width and humidity from Mode 1 recording b crack displacement waveforms from Mode 2 recording 3 1 Example of a multi hop network green lines represent reliable radio links between motes after Crossbow Technology Inc 20
115. ing the responses of the geophones connected to Shake n Wake boards and com paring them to the responses of the control geophones it can be determined whether or not the Shake n Wake circuitry will contaminate the waveform Figure A 2 clearly indicates that the positive portion of the output of a test geophone follows the positive portion of the output of its equivalent control geophone The negative portion of the output of the test geophone is 119 Figure A 1 Shake n Wake transparency test apparatus clipped at a value of 200 millivolts The negative portion of the output of a geophone attached to a Shake n Wake is clipped by reverse current limiting diodes that prevent voltage of inap propriate polarity from damaging the board s internal electronics When the same geophone is attached to the opposite connector on the Shake n Wake similar clipping of the positive por tion of the waveform can be observed These results show that the Shake n Wake satisfies the requirement of not corrupting the output of the geophone A 2 Verification of Trigger Threshold Idealized analysis of the Shake n Wake s adjustable trigger circuit pictured in Figure 3 24 indicates that for any trigger setting the threshold at which the Shake n Wake will bring the mote out of its low power sleep state is 3 558mV x To verify the validity of this idealized analysis the output of an HS 1 geophone is recorded on the same time scale as the
116. invented crack propagation gage for ACPS It has also examined the potential of the Crossbow Pro Series Wireless Sensor Network for use in ACPS The following conclusions can be drawn e The eKo Pro Series Wireless Sensor Network is suitable for use in ACPS provided is taken to accommodate its limited on board analog to digital conversion hardware e Both types of the evaluated commercially available crack propagation pattern may be used for ACPS however each has its disadvantages The TK 09 CPA02 005 DP can track crack tip position with a finer resolution however its non linear output causes the first 40 50 of its rung breaks to be undetectable by an mote The remaining 50 60 of its rung breaks however are easily detected The TK 09 CPC03 003 DP conversely is a larger gage with coarser resolution for crack to position This gage s linear output characteristics enable each of its individual rung breaks to be detected by the eKo mote e When applied to bare steel using the manufacturer specified elevated temperature cured adhesive both types of traditional crack propagation patterns are capable of functioning as ACPS sensors using motes When applied with a more field practical room temperature cured adhesive the adhesive has been shown to fail before the gage can break These gages are therefore only usable in field conditions where elevated temperature curing adhesive can be employed e Customized crack pr
117. ion flexibility and it even seems to draw less current than the LVDT Closer inspection of the sensor characteristics however reveals that the string potentiometer emerges as the clear choice for a wireless ACM application 31 The string potentiometer s maximum power draw is 7 mA at 35 DC However since the potentiometer is a purely resistive ratiometric device any voltage up to the manufacturer specified maximum of 35 V DC Firstmark Controls 2010 may be used to excite the sensor Thus by using a lower voltage to power the device the power consumption of the device can be lowered significantly below that of the LVDT or the eddy current sensor Even if one concedes that since ACM only measures the width of a crack once per hour or even for a fifteen second dynamic window the sensor will be powered off most of the time and thus not have a significant impact on overall power draw one must consider the warm up time of each device The LVDT and eddy current gages both use complex and temperature dependant signal conditioning electronics to achieve their specified precision This means that immediately after the sensors are powered on one must wait a certain amount of time before an accurate reading can be taken For the LVDT this time is an average of 2 minutes Puccio 2010 while the eddy current sensor can take up to 30 minutes Speckman 2010 to achieve its specified precision Though the measurement of crack width takes only a f
118. ion adds significantly to the time effort and manpower required to install an ACM system The existence of cables within an occupied structure also increases the chance of intentional and unintentional damage to the cabling by the structure s occupants indoor Basement Crack b Basement Level Figure 2 3 Plan view of an ACM system installed in a residence after Waldron 2006 10 2 3 1 Crack Width Sensors ACM systems utilize three different types of sensors to measure changes in widths of cracks Each of these sensors meets the precision and dynamic response characteristics required for ACM Siebert 2000 Ozer 2005 Figure 2 4 shows the three different types of crack width sensors used for ACM Linear variable differential transformers LVDTs eddy current dis placement gages and string potentiometers Table 2 1 compares the attributes of each type of crack width sensor and can suggest which sensor should be chosen for a given measurement scenario b Figure 2 4 Photographs of three types of crack width sensors a LVDT after McKenna 2002 b eddy current sensor after Waldron 2006 c string potentiometer after Ozer 2005 These three crack sensors that meet the requirements of precision and dynamic response uti lize significantly different physical mechanisms to measure the width of a crack Some sensors physically bridge the crack such that the movement of the crack can have an effect on the func tionalit
119. ion pattern configured to measure the growth of a crack resistance is measured between points A and B 88 4 5 Crack propagation patterns a TK 09 CPA02 005 DP narrow b TK 09 CPC03 003 DP wide 89 4 6 Crack propagation resistance versus rungs broken for a TK 09 CPA02 005 DP narrow b TK 09 CPC03 003 DP wide after Vishay Intertechnology Inc 2008 90 4 7 Schematic of the EEPROM mounted in the watertight connector assembly after Crossbow Technology Inc 2009c 91 4 8 Watertight ESB compatible cable assembly after Switchcraft Inc 2004 91 4 9 Diagram of sensor readout circuit adapted from Vishay Intertechnology Inc 2008 92 XX 4 10 4 11 4 12 4 13 4 14 4 15 4 16 4 17 4 18 4 19 4 20 4 21 4 22 Schematic of compact test specimen W 3 5 in B 0 5 in after for Testing and Materials 2006 94 Test coupon with a narrow gage and b wide gage installed 94 Photograph of experiment configuration for pre manufactured crack propagation gages 95 Test coupons with crack propagated through a narrow gage and b wide gage affixed with elevated temperature cured adhesive 96 Photograph of glue failure on wide gage affixed with room temperature cured adhesive the indicated region shows the glue failed before the gage 96 Data recorded by mote during tests of Coupons A and B 97 Schematic of a custom crack propagation gage crack grows to the right 3 V DC is applied between A and
120. irections other than along the length of the string but experience suggests that incidental motion of this type will not damage the sensor The sensor itself is smaller than either of the other two types of sensors however the eddy current displace ment sensor requires signal conditioning electronics to be placed on the wall near the sensor The enclosure for the electronics does not however need to be fastened as securely i e with epoxy as the sensor itself so removal of the sensor and its accompanying electronics will likely do less damage to paint and plaster than the other two displacement sensors The power draw of the string potentiometer is directly proportional to its input voltage the total resistance of the string potentiometer is 5000 Table 2 1 Comparison of the attributes of three types of crack width sensors 13 2 3 2 Velocity Transducers ACM systems make use of velocity transducers to measure two different physical phenomena particle velocity in the soil on which the structure is built and the motion of the structure itself 2 3 2 1 Traditional Buried Geophones Particle velocity in the soil the traditional mechanism by which mining industry regulators restrict the effect of blasting vibration at locations away from the blast site Dowding 1996 is measured using a large triaxial geophone shown in Figure 2 6 buried in the ground near a structure of interest When a blast wave propagates through the soi
121. is 117 APPENDIX A Experimental Verification of Shake n Wake This appendix describes experiments detailing experimental verification of the design criteria of the Shake n Wake board 118 The design criteria of the Shake Wake board are as follows 1 It must not significantly increase the power consumption of a mote 2 Its trigger threshold must be predictable and repeatable 3 It must not contaminate the output signal of its attached sensor 4 It must wake up the mote such that the mote has time to record during the peak of the motion of interest Criterion 1 is addressed in Section 3 3 7 3 Verification of the rest of the design critera are described in the following sections A 1 Transparency Because Shake n Wake is intended to be attached in parallel an analog to digital conver sion unit on the mote the output of the geophone must not be affected by the presence of the Shake n Wake To determine whether the Shake n Wake hardware meets this design criterion the output of the test geophones attached to Shake n Wake boards were compared to control geophones while subjected to identical physical excitation Figure 1 shows the experimen tal setup on which all four geophones an HS 1 test geophone an HS 1 control geophone a GS 14 test geophone and a GS 14 control geophone were placed on the end of a cantilevered aluminum springboard at an identical distance from the fulcrum By measur
122. is available If site conditions change such that radio communication between the base station and the mote is no longer possible that mote s data is no longer available More sophisticated WSNs make use of multi hop or mesh networking with self healing capabilities In this scenario each mote has the capability of transmitting and receiving data to and from any mote within its radio range This ability not only extends the physical range of the network i e motes can be deployed beyond the transmission distance to the base station but provides alternate paths for the data to travel should an intermediary mote become damaged or deplete its energy source Figure 3 1 shows an example of a WSN with multi hop capabilities This chapter examines both simple and sophisticated base stations rudimentary and ad vanced power management strategies and single and multi hop network topologies 3 1 2 Challenges of Removing the Wires from ACM The first and most obvious challenge to the creation of a wireless ACM system is power more specifically the fact that each mote is powered by a battery pack sometimes supplemented with a solar panel and not by direct connection to household power lines Because a main motivator in the transition from wired to wireless ACM is to minimize disruption to the resident of the in strumented structure frequent visits to change batteries or the use of large high capacity battery packs are unacceptable strategies
123. l the geophone generates a sinusoidal output that is observed by the ACM system at 1000 samples per second The ACM data logger will use this sensor s output to trigger high frequency recording of all relevant sensors in the system Figure 2 6 Photograph of a triaxial geophone with quarter for scale 14 2 3 2 2 Miniature Geophones In wired ACM systems smaller geophones can be used to measure the actual motion of the structure These smaller geophones are single axis devices and are therefore smaller than the geophone in Figure 2 6 These transducers measure velocity versus time which can then be integrated to reveal displacement versus time If the transducers are installed at the top and bottom of a wall section as shown in Figure 2 7 the recorded velocity measurements can be used to calculate the strains in the walls 5 51 CLUSTER Figure 2 7 Layout of miniature geophones such that wall strains be measured after McKenna 2002 In a wireless ACM system these same miniature geophones can serve the purpose of pro viding signal by which to alert wireless nodes to the occurrence of a significant vibratory event 15 Instead of relying on centrally installed geophone buried in the soil near the structure wire less system can utilize a geophone at every node to measure local vibration 2 3 3 Temperature and Humidity Sensors Indoor and outdoor temperature and humidity sensor
124. l Signal black red input white white output signal 5 red black ground common V S For crimping of hardware to displacement cable consider the 160001 01 installation kit Need something not shown Complete a Custom Solution Request All dimensions are REFERENCE and are in inches mm Data Sheet Series 150 Rev Privacy PolicyPrivacy Policy Firstmark Controls info Firstmarkcontrols com 1509001 2000 59100 Company 1176 Telecom Drive Creedmoor 27522 USA Phone 1 919 956 4203 Fax 919 682 3786 Toll Free 1 866 912 6232 Business hours Mon Fri 8 00am to 5 00pm Eastern time All specifications subject to change without notice 1996 2010 Firstmark Controls All rights reserved Newsletter gt News Representatives Request Literature CAD Models 3of3 Calculators B 3 MDA300CA Data Sheet MDA300 DATA ACQUISITION BOARD e Multi Function Data Acquisition Board with Temp Humidity Sensor Compatible with MoteView Driver Support Upto 11 Channels of 12 bit Analog Input Onboard Sensor Excitation and High Speed Counter Convenient Micro Terminal Screw Connections Applications Environmental Data Collection Agricultural and Habitat Monitoring Viticulture and Nursery Management HVAC Instrumentation and Control General Data Collection and
125. lization of one or both of the recording modes will directly constrain the choice of WSN platform on which to build the system Chapter 3 describes in detail hardware and software techniques employed to move an ACM system from the wired to the wireless domain Challenges regarding power consumption and sampling mode will be examined Chapter 3 will discuss the selection of the optimal sensors and WSN hardware to implement wireless ACM It will then discuss three versions of the wireless ACM system examining each system s design criteria hardware and software advancements and performance in test deployments Discussion focuses on issues of battery life multi hop mesh networking practicalities of system installation and the invention of a new device to allow commercially available hardware to better perform ACM functionality Chapter 4 will describe the design and development of an ACPS system using a WSN adapted from the agriculture industry Special attention is given to commercially available and newly invented crack propagation sensors to make more practical the use of ACPS on bridges Also described is the integration of sensors with the existing WSN system Finally Chapter 4 will summarize several laboratory experiments in which the WSN the commercially available sensors and the newly invented sensor were tested Chapter 5 presents conclusions and recommends future work Appendix A describes a set of experiments to verify the function
126. mote would be programmed with this calibration software and inserted into the MDA300CA already mounted near the crack When activated this calibration mote would transmit its readings several times per second so a PC plugged into the base station could view the real time output of the string potentiometer With this live display in hand the user could then center the string potentiometer in the middle of its range tighten down the screws and replace the calibration mote with a mote programmed with MDA300Logger 3 3 4 4 Deployment in Test Structure Ozer 2005 performed detailed analysis of the data that was collected using Version 1 of the wireless ACM system His work concluded that for during its entire operational period lasting from November 18 2004 through January 16 2005 the wireless ACM system based on MDA300Logger performed similarly to a wired ACM system monitoring the same crack over the same time period Figure 3 8 shows that both systems measured the same general trends in temperature and crack displacement over the two month period 43 6002 1920 Joye porred puou omy 1591 545 WOY pue Aq sjuourognseour juourooe dsrp xoe1o pue 1976 aun mu 50 21 80 10 80 1 50 17 90 1 02 08 or luin suetusoed si 7 9 10 1
127. mous Crack Monitoring 111 5 2 2 Wireless Autonomous Crack Propagation Sensing 112 References 113 Appendix A Experimental Verification of Shake n Wake 117 Transparency 118 A 2 Verification of Trigger Threshold A 2 1 Physical Meaning of Trigger Threshold A 3 Speed A 4 Discussion A 4 1 Upper Frequency Limit Shake n Wake Response Time A 4 2 Lower Frequency Limit Geophone Output Amplitude A 5 Appendix Conclusion Appendix B Data Sheets and Specifications MICA2 Data Sheet B 2 String Potentiometer Data Sheet B 3 Data Sheet B 4 MIBSIOCA Data Sheet B 5 Stargate Data Sheet B 6 Alkaline Battery Data Sheet B 7 Lithium Battery Data Sheet B 8 GS 14 Geophone Data Sheet B 9 HS 1 Geophone Data Sheet B 10 UC 7420 Data Sheet B 11 Bus Resistor Data Sheet B 12 Conductive Pen Data Sheet B 13 Bridge Paint Data Sheet xi 119 123 124 127 128 129 129 131 132 134 137 138 139 141 143 145 148 151 154 156 158 2 1 3 1 3 2 3 3 4 1 A 1 xiii List of Tables Comparison of the attributes of three types of crack width sensors 12 Distribution of MICA2 based wireless ACM Version 2 packets over the parents to which they were sent 58 ACM related commands added to xcmd by Version 3 of the MICA2 based wireless ACM software 70 Results of filtering Version 3 wireless ACM potentiometer readings 78 Change in eKo ADC steps for first rung break for each comb
128. n Wake board does not have the ability to digitally record the readings from the sensor to which it is attached It is therefore crucial to the operation of a system perform ing Mode 2 recording that the mote to which the Shake n Wake is attached begins to operate and execute user code as quickly as possible as it will be the user code that is responsible for 125 Trigger threshold vs motion frequency GS 14 0 5 T T T T s i 4 g 3 069 t me 069 ips 5 3 1 955 ips 5 x 02 F 4 s 5 5 5 i gt 01 F 4 x i measured theoretical 0 1 1 1 1 5 10 15 20 motion frequency Hz Trigger threshold vs motion frequency HS 1 0 016 T T T 0 014 4 i 4 n a 2 5 0 01 F 4 E 0 008 4 2 A 8 0006 X 4 3 gt 0 004 T 4 measured i 442 i i theoretical AX 5 10 15 20 motion frequency Hz Figure 7 Summary of Shake n Wake level 2 trigger threshold velocities recording the event If a wireless ACM system were deployed to measure dynamic response of a residential structure the highest frequency input signal to which the Shake n Wake must respond is 20 hertz this is the highest expected frequency of motion of an instrumented wall 126 Figure 8 shows that a 20 hertz zero centered sinusoidal input signal will reach its peak abso lute amplitude after 12 5 millisec
129. ng Support for wireless remote reprogramming Wide range of sensor boards and data acquisition add on boards MoteWorks enables the development of custom sensor applications and is specifically optimized for low power battery operated networks MoteWorks is based on the open source TinyOS operating system and provides reliable ad hoc mesh networking over the air programming capabilities cross development tools server middleware for enterprise network integration and client user interface for analysis and configuration E mail info xbow com Processor and Radio Platform MPR400 The MPR400 is based on the Atmel ATmega128L The ATmega128L is a low power microcontroller which runs MoteWorks from its internal flash memory A single processor board MPR400 can be configured to run your sensor application pro cessing and the network radio communications stack simultane ously The MICA2 51 pin expansion connector supports Analog Inputs Digital I O I2C SPI and UART inter faces These interfaces make it easy to connect to a wide variety of exter nal peripherals Sensor Boards Crossbow offers a variety of sensor and data acquisition boards for the MICA2 Mote All of these boards con nect to the MICA2 via the standard 51 pin expansion connector Custom sensor and data acquisition boards are also available Please contact Cross bow for additional information Document Part Number 6020 0042 08 Rev A Web www
130. ng Annex Specifications are subject to change without notice Customers should verify actual device performance in their specific applications For information on specific applications download Bourns application notes DRAM Applications Dual Terminator Resistor Networks R 2R Ladder Networks SCSI Applications 4600X Series Th Isolated Resistors 102 Circuit Model 4600X 102 RC 4 6 8 10 12 14 Pin These models incorporate 2 to 7 isolated thick film resistors of equal value each connected between two pins Resistance Tolerance sati ohm 2 96 5 96 10 ohms to 49 ohms 50 ohms to 5 megohms Above 5 megohms Power Rating per Resistor BET 0 30 Power Temperature Derating Curve WATTS 0 25 15 AMBIENT TEMPERATURE C ck Film Conformal SIPs Bussed Resistors 101 Circuit Model 4600X 101 RC UT uh These models incorporate 3 to 13 thick film resistors of equal value each connected between a common bus pin 1 and a separate pin Resistance Tolerance 10 ohms to 49 ohms 50 ohms to 5 megohms Above 5 5 1 ohm 2 96 th 96 Power Rating per Resistor At 70 C 0 20 watt Power Temperature Derating Curve 80 50 40 30 WATTS 20 10
131. nicians and manufacturers will find that Max Temperature 400 F 205 C the CircuitWorks Conductive Pen speeds Tack Free Time 25 C 3 to 5 Minutes project completion and cuts rework time Cure Time 25 C 20 to 30 Minutes Solder Wetting 2 to 3 Seconds Single component system Electrical Conductivity Excellent High electrical conductivity Adhesion Excellent Fast drying Flexibility Good Highly adherent to circuit boards Chemical Resistance Good Operating temperature to 400 F 205 C Tip Diameters MTP 0 8 mm 0 03 inches STP 1 2 mm 0 05 inches TYPICAL APPLICATIONS Shelflife 12 months CircuitWorks Conductive Pen may be used for electronics applications including COMPATIBILITY Circuit Trace Repair Solderless Linking of Components EMI Shielding Solderable Terminations Quick Prototype Modifications CircuitWorks Conductive Pen material has excellent compatibility with materials used in printed circuit board fabrication As with any chemical system compatibility with the substrate must be determined on a non critical area prior to use USAGE INSTRUCTIONS Read MSDS carefully prior to use Cleaning For best adhesion clean board with one of Chemtronics Electro Wash or Pow R Wash solvents in order to remove surface contamination which may prevent adequate material contact Mixing Although this system has been formulated to resist hard packing it should be shaken vigorously for 30 second
132. onds c first peak at quarter of the period Singal amplitude period 0 05 L L 0 0 0125 0 025 0 0375 0 05 Time sec Figure A 8 20 hertz sinusoidal input signal with rise time of 12 5 milliseconds If it is assumed that the mote must be awake for at least one full sample length before the peak of interest and that it will be sampling at 1000 hertz then it follows that the time from Shake n Wake event detection to the execution of user code by the mote must be less than 11 5 milliseconds Output from an oscilloscope connected to various components of a wireless ACM node shown in Figure A 9 illustrates signal propagation delay from the geophone through the com ponents of the Shake n Wake and finally into the mote s processor At time t 605 the out put voltage of the geophone shown in yellow crosses the threshold V which corresponds to the software programmable threshold residing in the Shake n Wake s memory 58 8 later at time t2 the Shake n Wake s hardware interrupt request line IRQ shown in green changes to logic low This change in state of the IRQ is the wakeup signal passing from the Shake n Wake to 127 the mote The mote which is asleep until t2 has already been programmed by the user with an instruction to turn on an LED The LED active low hardware line shown in purple activates at 1 318 after the signal from the Shake n Wake is sent to the mote The activation of the LED in
133. opagation gages made from conductive ink and commercially available bus resistor networks can track crack propagation and conform to the eKo 108 motes strict analog specifications These gages can be applied at room temperature without adversely affecting sensor functionality Customized crack propagation gages allow for a single gage to track the propagation of a crack whose direction of propaga tion might be unknown or difficult to characterize 109 5 Conclusion 5 1 Conclusion The preceding chapters have described the fundamentals of two wireless systems of au tonomous monitoring of cracks Autonomous Crack Monitoring ACM and Autonomous Crack Propagation Sensing ACPS ACM systems correlate the changes in the widths of cosmetic cracks in residential structures with nearby vibration and with environmental effects to deter mine causal relationships ACPS systems use crack propagation sensors affixed to steel bridge members to track the propagation of existing cracks alerting stakeholders to any growth Wired versions of these systems are expensive to install and intrusive to the users of the structures they monitor As wireless sensor networks WSNs decrease in size and cost and increase in capa bility and longevity migrating ACM and ACPS systems from the wired to the wireless domain will drastically decrease the time and cost of system installation as well as the disruption to the users of instrumented structu
134. oroughly mixed after sweat i Apply paint at the recommended film thickness and spreading rate as indicated below Recommended Spreading Rate per coat M um Maximum Wet mils microns 7 0 175 13 5 338 Dry mils microns 5 0 125 10 0 250 sq ft gal m L 116 2 8 232 5 7 Theoretical coverage sq ft gal m 1 mil 28 microns at 1152 28 2 May be applied at 3 0 10 0 mils dft as an intermediate coat Refer to Recommended Systems page 2 NOTE Brush or roll application may require multiple coats to achieve maximum film thickness and uniformity of appearance Drying Schedule 7 0 mils wet 175 microns 35 F 1 77C 25 100 F 38 C 50 RH To touch 4 5 hours 2 hours 1 5 hours To handle 48 hours 8 hours 4 5 hours To recoat mi um 48 hours 8 hours 4 5 hours maximum 1 year 1 year 1 year To cure Service 10 days 7 days 4 days Immersion 14 days 7 days 4 days If maximum recoat time is exceeded abrade surface before recoating Drying time is temperature humidity and film thickness dependent Paint temperature must be at least 40 F 4 5 C minimum Pot Life 10 hours 4 hours 2 hours Sweat in time 30 minutes 30 minutes 15 minutes When used as an intermediate coat as part of a multi coat system Drying Schedule 5 0 mils wet 125 microns 35 F 1 7 C 77 F 25 C 100 F 38 C 50 RH To touch 3 hours 1 hour 1 hour To handle 48 hours 4 hours
135. pagation does not require as sophisticated a data logger as does the monitoring of crack width changes with respect to vibration though it does require specialized crack propagation patterns Regardless of the chosen sensor and the makeup of a crack measurement system the instal lation of any wired system is labor intensive and expensive high quality instrument wires must be run through the monitored structure typically an occupied residence in the case of ACM and an active highway bridge in the case of ACPS The need to minimize installation time cut down on the cost and labor of installing wires and minimize intrusiveness to the user s of a structure over the course of the monitoring project clearly demonstrates the utility of wireless monitoring systems Chapters 3 and 4 will examine the construction of such systems 25 3 Techniques for Wireless Autonomous Crack Monitoring 3 1 Chapter Introduction The ever decreasing size and increasing performance of computer technology suggest that an expensive labor intensive and residentially intrusive wired Autonomous Crack Monitoring ACM system may be replaced by a similarly capable easier to install yet less expensive and intrusive wireless ACM system based on existing commercially available wireless sensor networks The implementation of a wireless ACM system with all the functions of a standard ACM system i e Mode 1 and Mode 2 recording capability no requirement fo
136. prior to coating Solvent Clean per SSPC SP1 recommended solvent is VM amp P Naphtha When weathering is not possible or the surface has been treated with chro mates or silicates first Solvent Clean per SSPC SP1 and apply a test patch Allow paint to dry at least one week before testing adhesion If adhesion is poor brush blasting per SSPC SP7 is necessary to remove these treatments Rusty galvanizing requires a minimum of Hand Tool Cleaning per SSPC SP2 prime the area the same day as cleaned Concrete and Masonry For surface preparation refer to SSPC SP13 NACE 6 or ICRI 03732 CSP 1 3 Surfaces should be thoroughly clean and dry Concrete and mortar must be cured at least 28 days 75 F 24 C Remove all loose mortar and foreign material Surface must be free of laitance concrete dust dirt form release agents moisture curing membranes loose cement and hardeners Fill bug holes air pockets and other voids with Steel Seam FT910 Concrete Immersion Service For surface preparation refer to SSPC SP13 NACE 6 Section 4 3 1 or 1 3 2 or ICRI 03732 CSP 1 3 Always follow the standard methods listed below ASTM D4258 Standard Practice for Cleaning Concrete ASTM D4259 Standard Practice for Abrading Concrete ASTM 04260 Standard Practice for Etching Concrete ASTM F1869 Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete SSPC SP 13 Nace 6 Surface Preparation of Concrete ICRI 03732 Concrete Surface Preparation P
137. proof of concept designed to demonstrate the viability of a MICA2 based implementation of ACM by implementing Mode 1 recording Version 2 incorporated new wire less mesh networking and power management libraries to implement Mode 1 recording with more reliability and system longevity Version 3 incorporated the design and manufacture of a new sensor board the Shake n Wake to allow data to be taken at random times rather than scheduled times without sacrificing system longevity The following conclusions can be drawn e The MICA2 WSN platform combined with MDA300CA sensor boards and string po tentiometers is capable of performing Mode 1 recording for approximately 30 days The MDA300CA is essential as the internal ADC on the MICA2 does not have suffi cient resolution or front end gain for the expected potentiometer output e Intelligent power management software based on the XMesh routing layer can be used with the MICA2 MDA300CA potentiometer system to operate a fully functional Mode 1 system for six to twelve months e Battery longevity is is dependant on the ambient temperature and humidity of the de ployment environment e A robust industrially rated and fully enclosed GNU Linux embedded computer can be combined with an MIB510CA board to create a reliable and secure Internet accessible base station that can continue to collect data even while the Internet connection might be off line Such a base station can also be used to modify the WSN
138. r an on site personal computer for system operation a small enough footprint such that it will not disturb the resident of the instrumented structure a sensor suite that can be operated with minimal power use and system operation for at least six months without a battery change or any other human intervention is fraught obvious and non obvious challenges 3 1 1 Wireless Sensor Networks Wireless sensor networks WSNs consist of a network of nodes or motes that communicate with one or more base stations via radio links Most WSNs transmit in the low power license free ISM industrial scientific and medical band typically between 420 and 450 megahertz In general motes are designed to be low cost relatively interchangeable and in many cases redundantly deployed 26 3 1 1 1 Motes Each mote is made up of a processing unit a radio transceiver a power unit and a sensing unit The two main components within the sensing unit are an analog digital converter ADC and software switchable power sources to activate and deactivate sensors The sensors ADCs and switchable power supplies are either integral to the mote itself or added by means of an external sensor board that is physically attached to the mote In none of the WSNs described in this thesis does any data processing occur on the motes themselves all data is transmitted back to the base station before any data processing might occur For more detail on motes and
139. r is required for complete mixing of color Tinting is not recommended for immersion service APPLICATION CONDITIONS 35 F 1 7 C minimum 120 F 49 C maximum air and surface 40 F 4 5 C minimum 120 F 49 C maximum material At least 5 F 2 8 C above dew point Relative humidity 85 maximum Refer to product Application Bulletin for detailed application information Temperature ORDERING INFORMATION Packaging PartA 1 gallon 3 78L and 5 gallon 18 9L containers Part B 1 gallon 3 78L and 5 gallon 18 9L containers Weight 12 9 0 2 Ib gal 1 55 mixed may vary by color SAFETY PRECAUTIONS Refer to the MSDS sheet before use Published technical data and instructions are subject to change without notice Contact your Sherwin Williams representative for additional technical data and instructions WARRANTY The Sherwin Williams Company warrants our products to be free of manufactur ing defects in accord with applicable Sherwin Williams quality control procedures Liability for products proven defective if any is limited to replacement of the defec tive product or the refund of the purchase price paid for the defective product as determined by Sherwin Williams NO OTHER WARRANTY OR GUARANTEE OF ANY KIND IS MADE BY SHERWIN WILLIAMS EXPRESSED OR IMPLIED STATUTORY BY OPERATION OF LAW OR OTHERWISE INCLUDING MER CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE www
140. r transferring files to and from remote computer systems over a network Web Server httpd WinCE IIS including ASP ISAPI Secure Socket Layer support SSL 2 SSL 3 and Transport Layer Security TLS SSL 3 1 public key based protocols and Web Administration ISAPI Extensions Dial up Networking Service RAS client API and PPP supporting Extensible Authentication Protocol EAP and RAS scripting Application Development Software Moxa WinCE 5 0 SDK C Libraries and Run times Component Services COM and DCOM Microsoft Foundation Classes MFC Microsoft NET Compact Framework 2 0 SP2 XML including DOM XQL XPATH XSLT SAX2 SOAP Toolkit Winsock 2 2 n n B Mj Roady O um p 3 Console E 6 9 9 69 t HER l pua ge i 197 mm 7 767 Ordering Information Available Models r Package Checklist UC 7410 LX Plus RISC based IXP425 embedded computer with 8 serial ports dual LANs 1UC 7410 or UC 7420 computer Linux 2 6 Wall mounting kit UC 7410 CE RISC based 422 embedded computer with 8 serial ports dual LANs WinCE DIN Rail mounting kit 5 0 UC 7420 LX Plus RISC based IXP425 embedded computer with 8 serial ports dual LANs USB PCMCIA CompactFlash Linux 2 6 UC 7420 CE RISC based IXP422 embedded computer with 8 serial port
141. rack propagation pattern a brittle paper thin coupon on which a ladder like pattern of electrically conductive material is printed This coupon is glued to the surface of the material at the tip of the crack as shown in Figure 4 4 When the crack elongates and breaks the rungs of the pattern the electrical resistance between the sensor s two terminals will change This resistance is be read using an eKo mote to record the distance the crack has propagated A crack direction of propagation Figure 4 4 Cartoon of a crack propagation pattern configured to measure the growth of a crack resistance is measured between points A and B B Vishay Intertechnology Inc manufactures commercially a series of these crack propaga tion patterns Two of these sensors were chosen for use in an ACPS system the TK 09 CPA02 005 DP or narrow gage shown in Figure 4 5a and the TK 09 CPC03 003 DP or wide gage shown in Figure 4 5b Both sensors allow for the measurement of twenty distinct crack lengths 89 with their twenty breakable grid lines The narrow gage s grid lines spaced 0 02 inches apart while the wide gage s grid lines are spaced 0 08 inches apart Additionally the narrow gage s resistance varies non linearly with the number of rungs broken as shown in Figure 4 6a while the wide gage s resistance varies linearly with number of rungs broken as shown in Figure 4 6b This linear behavior o
142. raction of a second the warm up times of the LVDT and eddy current sensors would draw several orders of magnitude more power than would a string potentiometer that requires no warm up time to take a precise measurement Thus the string potentiometer is the clear choice for measurements of crack width in wireless ACM applications The string potentiometer pictured in Figure 3 2 is a three wire ratiometeric displacement measurement sensor with a stroke length of 1 5 inches At a position of zero inches i e when the potentiometer cable is fully retracted into its housing the resistance measured between the white output lead and black ground lead is 00 and the resistance measured between the white output lead and red DC input lead is 500022 At any cable position between fully retracted and 32 fully extended the resistance measured between the white and black leads is proportional to the distance the cable has been pulled out of its housing To operate the sensor a known DC voltage is placed across the red and black leads and the voltage between the white and black leads is measured The distance of cable extension is the ratio of output voltage to the input voltage times 1 5 inches Technical specifications of the string potentiometer may be found in Appendix B 2 Figure 3 2 Photograph of a string potentiometer with quarter for scale after Jevtic et al 2007b Installation of the string potentiometer is accomplished using two simpl
143. reases as crack propagates This type of sensor has advantages and disadvantages over the crack width measurement strategy of measuring crack activity The obvious advantage of such a crack propagation sensor is that it will directly measure the crack behavior in which a homeowner is interested the exten sion of a crack A traditional crack propagation sensor is also typically an order of magnitude less costly than a typical crack width measurement sensor described in Section 2 3 1 above 21 2 4 2 1 Traditional Crack Propagation Patterns Traditional crack propagation gages are designed to be chemically bonded to a substrate that has crack or is predicted to crack The gages shown in Figure 2 10 are made up of a high endurance K alloy foil grid backed by a glass fiber reinforced epoxy matrix Vishay Intertechnology Inc 2008 Though these gages are proven to be useful in the measurement of cracking in mate rials such as steel or ceramic their usefulness for measuring cracks in residential structures is diminished due to the fact that the glass fiber reinforced epoxy backing is much stronger than the drywall or plaster to which it would be affixed as part of an ACM system Marron 2010 Additionally it is not difficult to imagine that a propagating crack may alter its direction be fore breaking the rungs of the crack propagation gage which would render the gage ineffective Chapter 4 describes a method in which these sensors can be applied
144. reference and a 1 precision resister Jevtic et al 2007 Figure 3 24 shows a simplified diagram of the voltage comparison circuitry Vomp the reference voltage to which the geophone output is compared is directly determined by the position of the wiper x which is an integer between 0 and 31 inclusive Thus the threshold voltage to which the input voltage is compared is Veomp 3 558 where Veomp is the threshold voltage in millivolts and z is the setting 0 31 of the potentiome ter 65 pel R2 ANW x 32 100K Vcomp w e u x 5 o 5 S N N AGND Figure 3 24 Simplified Shake n Wake reference circuit diagram 3 3 7 Hardware Like Versions 1 and 2 Version 3 consisted of several MICA2 motes equipped with MDA300CA sensor boards string potentiometers and two AA batteries Version 3 nodes also included a single Shake n Wake board and a geophone Figure 3 25 shows a photograph of a fully assembled Version 3 node The base station was significantly changed from the base station used with Version 2 First the Stargate was replaced with a commercially available Moxa UC 7420 RISC based GNU Linux embedded computer The Stargate was found to be too physically fragile for prac tical use without the creation of a fully customized enclosure The UC 7420 ships from the factory in a rugged metal enclosure designed for industrial use
145. res Chapter 2 described the sensors and components that make up ACM and ACPS systems Chapter 3 described the challenges associated with moving an ACM system from the wired to the wireless domain sensor optimization minimization of power consumption and dynamic event detection Chapter 3 introduced the commercially available MICA2 WSN platform and described three versions of a wireless ACM system built upon it each with its own test deploy ment case study 110 The three test deployments in Chapter 3 showed that with the proper power and network management software components the MICA2 based wireless ACM system is well suited to Mode 1 recording periodic single point measurements taken from all sensors in a structure over a period of six to twelve months before a battery change is necessary The test deploy ments showed that with the invention of the Shake n Wake hardware expansion board for the MICA2 WSN platform Mode 2 recording high frequency recording whenever an event of in terest is detected can be partially implemented without sacrificing battery longevity Though Shake Wake made possible low power event detection limitations in the existing software drivers for the data acquisition board in the MICA2 based system prohibited triggered high frequency sampling of all sensors Chapter 4 introduced the Pro Series WSN a commercially available product designed for the agriculture industry but with capabilities that len
146. reviously Painted Surfaces If in sound condition clean the surface of all foreign material Smooth hard or glossy coatings and surfaces should be dulled by abrading the surface Apply a test area allowing paint to dry one week before testing adhesion If adhesion is poor or if this product attacks the previous finish removal of the previous coating may be necessary If paint is peeling or badly weathered clean surface to sound substrate and treat as a new surface as above Surface Preparation Standards Condition of 150 8501 1 Swedish Std Surface 57079 1 515055900 SSPC NACE White Metal 5 5 SP5 1 Near White Metal a 2 5 a 2 5 P io 2 Commercial Biast 8a2 8a2 6 3 Brush Of ai ai 8B 4 ing Ruste h Hand Tool Cleaning Rusted 532 53 i uster t t Power Tool Cleaning Pitted amp Rusted D St 3 553 Temperature 35 F 1 7 C minimum 120 F 49 C maximum air and surface 40 F 4 5 C minimum 120 F 49 C maximum material At least 5 F 2 8 C above dew point Relative humidity 85 maximum APPLICATION EQUIPMENT The following is a guide Changes in pressures and tip sizes may be needed for proper spray characteristics Always purge spray equipment before use with listed reducer Any reduction must be compliant with existing VOC regulations and compatible with the existing environmental and application conditions Reducer Clean Up Reducer R7K15 In
147. riment translated into terms of particle velocity Over the frequency range of interest the response of an undamped HS 1 geophone can be determined using the factory calibration sheet included in Appendix B 9 The GS 14 geophone however is not typically used for detection of low frequency motion so 124 the relationship between its voltage and frequency has not been included in the factory calibra tion curve in Appendix B 8 Its low frequency response can be extrapolated from the factory provided curve using a power law formula as follows The cantilever vibration displacement 6 can be held constant during the experiment by ap plying identical tip displacement Its velocity is then equal to 2r f Even with a constant the velocity increases linearly for the portion of the GS 14 s response curve where frequency 1s less than 20 hertz Therefore the portion of the GS 14 s response curve can be described with the following power law formula v 2 where is the frequency of motion is a constant that depends on the damping of the geophone n is the slope of the response curve on a logarithmic plot and v is the voltage per inch per second of geophone output at frequency f For the undamped response curve A used in this experiment to provide the largest signal to noise ratio to the Shake Wake board this portion of the response curve can be approximated as 2 455 x 1075 81 A 3 Speed The Shake
148. rities This wiring ensures that both the positive and negative portions of the geophone output will be considered in determining whether the triggering threshold is crossed CN3 passes its input signal directly to a comparator that compares the positive portion of the input waveform to the user specified threshold while ignoring the negative portion CN4 passes the inversely polarized input signal to a second identical comparator which compares the negative portion of the input waveform to the threshold while ignoring the positive portion The same user supplied threshold is applied to both signals Either connector can be disabled using the jumper switches and J2 Jumper J3 provides the ability to select the interrupt controller address on the MICA2 s processor over which the Shake n Wake can communicate the occurrence of a threshold crossing thus ensuring compatibility with other sensor boards that might also need to interrupt the mote s processor Jevtic et al 2007 The voltage input threshold at which the Shake Wake board will wake up the mote s main control processor can be set in software by the user both before and after deployment of the mote The variability of the trigger threshold is achieved by using a programmable potentiometer with a 32 position electronically reprogrammable wiper which is placed in series 64 Figure 3 23 The Shake Wake sensor board after Jevtic et al 2007a with a precision 1 263 V DC
149. roperties Shelf Life 36 months unopened Store indoors at 40 F 4 5 C to 100 F 38 C 91 F 33 C TCC mixed Reducer R7K15 Flash Point Reducer Clean Up RECOMMENDED USES CHARACTERISTICS Finish Semi Gloss Color Mill White Black and a wide range of colors available through tinting Volume Solids 72 2 mixed Mill White Weight Solids 85 2 mixed Mill White VOC EPA Method 24 Unreduced 250 g L 2 08 Ib gal mixed Reduced 10 300 g L 2 50 Ib gal Mix Ratio 1 1 by volume Recommended Spreading Rate per coa Minimum Maximum Wet mils microns 7 0 175 13 5 338 Dry mils microns 5 0 125 10 0 250 Coverage sq m L 116 2 8 232 5 7 Theoretical coverage sq ft gal mL mil 28 microns git 1152 28 2 May be applied at 3 0 10 0 mils dft as an intermediate coat Refer to Recommended Systems page 2 NOTE Brush or roll application may require multiple coats to achieve maximum film thickness and uniformity of appearance Drying Schedule 7 0 mils wet 175 microns 35 1 7 77 25 100 38 50 RH To touch 4 5 hours 2 hours 1 5 hours To handle 48 hours 8 hours 4 5 hours To recoat minimum 48 hours 8 hours 4 5 hours maximum 1 year 1 year 1 year To cure Service 10 days 7 days 4 days Immersion 14 days 7 days 4 days If maximum recoat time is exceeded abrade surface before recoating Drying time i
150. rsion 3 wireless ACM nodes located a on the underside of the service stairs b over service stair doorway to kitchen and c on the wall of the main stairway d the base station in the basement Plots of a temperature b humidity c battery voltage and d parent mote address recorded by Version 3 of the wireless ACM system over the entire deployment period Plots of a temperature b humidity c crack displacement and d Shake n Wake triggers recorded by the Version 3 of the wireless ACM system over the 75 day period of interest Comparison of battery voltage versus time for the Version 2 and Version 3 wireless ACM systems Plot of three separate sets of crack width data as recorded by Mote 3 of the Version 3 wireless ACM system 67 68 TI 72 74 75 76 77 78 3 35 Plots of a humidity and b temperature versus filtered crack displacement recorded by the Version 3 wireless ACM system over the 75 day period of interest 79 4 1 Fatigue crack at coped top flange of riveted connection after United States Department of Transportation Federal Highway Administration 2006 85 4 2 Fatigue crack marked as per the BIRM after United States Department of Transportation Federal Highway Administration 2006 85 4 3 a eKo Pro Series WSN including base station after Crossbow Technology Inc 20092 b Individual eKo mote with 12 inch ruler for scale 87 4 4 Cartoon of a crack propagat
151. s dual LANs USB PCMCIA CompactFlash WinCE 5 0 Ethernet cable RJ45 to RJ45 cross over cable 100 cm CBL RJ45F9 150 8 pin RJ45 to 089 female console port cable 150 cm CBL RJ45M9 150 8 RJ45 to 089 male serial port cable 150 cm Universal power adaptor Document and Software CD Quick Installation Guide printed Product Warranty Statement printed Moxa Inc All Rights Reserved Updated Mar 17 2010 Specifications subject to change without notice Please visit our website for the most up to date product information 153 B 11 Bus Resistor Data Sheet BOURNS Product Characteristics Resistance Range 10 ohms to 10 megohms Maximum Operating Voltage 100 V Temperature Coefficient of Resistance 50 Q to 2 2 100 below 50 above 2 2 TCR Tracking 50 maximum equal values Resistor Tolerance See circuits Insulation Resistance 10 000 megohms minimum ithstanding Voltage Dielectric Operating Temperature nt 55 C to 125 C Environmental Characteristics TESTS PER MIL STD 202 Short Time Overload Load Life Moisture Resistance Resistance to Soldering Terminal Strength Thermal Shock Physical Characteristics Flammability Conforms to UL94V 0 Body Material Epoxy resin Standard Packaging Bulk Ammo pak available How To Order
152. s such as those shown in Figure 2 8 are utilized to record long term trends in temperature and humidity both inside and outside an instrumented structure The outdoor gage supplies useful information about the passage of weather fronts and seasonal weather trends The indoor gage supplies relevant information about the activity of the furnace or air conditioning system in the house Both data streams can be correlated to crack response as discussed in section 2 4 1 1 a b Figure 2 8 Photographs of a indoor and b outdoor temperature and humidity sensors after Waldron 2006 2 4 Types of Crack Monitoring Crack behavior in response to vibration or environmental effects can manifest itself through a number of different physical changes in the crack The crack can elongate open i e widen 16 and close see direction A in Figure 2 5 shear along the axis of the crack see direction B in Figure 2 5 or move out of plane see direction C in Figure 2 5 Measurement of each of these types of motion can lend insight into their causes 2 4 1 Width Change Monitoring ACM systems are largely concerned with measurements of changes in crack widths Though the most serious crack activity to a homeowner might be extension or propagation of the crack rather than opening or closing of the crack it is reasonable to assume the driving force behind any elongation will in fact be the same driving force behind widening and contracting
153. s batteries faster than the other motes Because alkaline batteries powered the motes motes at lower temperatures would likely have less battery longevity than motes at higher temperatures Figure 3 18 shows ambient tem peratures recorded by each mote over the total deployment period It is clear that the ambient temperatures recorded by Mote 2 were not higher or lower than the temperatures recorded by the other three motes so it is unlikely that temperature played a role in the early battery depletion The only physical quantity that has any correlation with the early depletion of the batteries attached to Mote 3 is ambient relative humidity Figure 3 19 shows that the ambient relative humidity measured in the basement of the main structure is significantly higher in the period between days 100 and 150 than that measured by the other motes This increased humidity may have led to corrosion of the battery or the mote s battery terminals which would have adversely affected battery life In future deployments any negative effect of increased relative humidity could be negated by placing the motes in sealed enclosures and applying silicone to the battery terminals 60 3 3 6 MICA2 Based Wireless ACM Version 3 Shake n Wake Mode 2 recording requires an ACM system to have the ability to determine whether a vibratory event has occurred and is of sufficient magnitude to be deemed an event of interest Tradi tional wired ACM systems make this de
154. s temperature humidity and film thickness dependent Paint temperature must be at least 40 F 4 5 C minimum Pot Life 10 hours 4 hours 2 hours Sweat in time 30 minutes 30 minutes 15 minutes When used as an intermediate coat as part of a multi coat system Drying Schedule 5 0 mils wet 125 microns 35 1 7 Q9 77 25 100 38 50 RH To touch 3 hours 1 hour 1 hour To handle 48 hours 4 hours 2 hours To recoat minimum 16 hours 4 hours 2 hours maximum 1 year 1 year 1 year Marine applications Fabrication shops Refineries Pulp and paper mills Chemical plants Power plants Tank exteriors Offshore platforms Water treatment plants Mill White and Black are acceptable for immersion use for salt water and fresh water not acceptable for potable water Suitable for use in USDA inspected facilities Conforms to AWWA D102 03 OCS 5 Conforms to MPI 108 PERFORMANCE CHARACTERISTICS Substrate Steel Surface Preparation SSPC SP10 NACE 2 System Tested 1 ct Macropoxy 646 Fast Cure 6 0 mils 150 microns dft unless otherwise noted below Test Name Test Method Results ASTM D4060 517 wheel 84 mg loss 1000 cycles 1 kg load Accelerated ASTM D4587 QUV A Weathering QUV 12 000 hours Adhesion ASTM D4541 1 037 psi Rating 10 per ASTM 0714 for blistering Rating 9 per Abrasion Resistance Passes Corrosion Weathering D5894 36 cycles 1
155. s to insure the proper dispersion of the silver flakes If pen has been allowed to sit idle for a long period of time the mixing ball may seize in the barrel To free the ball use force to tap the barrel end of the pen until the ball begins to move inside the pen Application The conductive ink is dispensed through the CircuitWorks Conductive Pen Squeezing the pen body while pressing down on the surface will allow the material to flow enabling the trace to be drawn Practice with the pen before attempting detail work The bulk form of this material may be applied by brushing banding or automatic dispensing equipment Thinning The conductive ink has been optimized for the CircuitWorks Conductive Pen and thinning is not normally necessary However Butyl Acetate may be added with thorough mixing to make slight adjustments for ease of application in the bulk form Clean up Removal The conductive ink may be cleaned or removed using a strong organic solvent such as Chemtronics Electro Wash PX Curing Tack free in 3 to 5 minutes at room temperature Achieves electrical conductivity within 30 minutes Heat cure for 5 minutes at 250 to 300 F 120 to 150 C for maximum conductivity durability and chemical resistance 157 Soldering Low temperature soldering is possible to the heat cured silver conductive traces if done at 350 F 177 C for lt 5 seconds AVAILABILITY CW2200STP 8 5 g 0 3 oz Standard 1 2 mm tip CW
156. ssor Dowding took on the arduous task of an alyzing data collected by one of the systems in Chapter 3 several years after it was archived Mr Meissner worked diligently with this unfamiliar data and in extremely short order produced information that I used to further my analysis Martin Turon Director of Software Engineering at Crossbow Technology was not only responsible for the development of all of the software which I later modified to implement the systems described in Chapter 3 but he made himself available to me for personal consultation after I met him at Crossbow s headquarters in 2005 Mr Turon s patience and helpful insights as I struggled to understand the vastness of the Crossbow code library were invaluable Mohammad Rahimi of the Center for Embedded Networked Sensing at the University of California Los Angeles designed and developed the MDA300CA sensor board which was integral to all of the work described in Chapter 3 Dr Rahimi provided me with technical support and guidance in my efforts to adapt the MDA300CA to wireless ACM The experiments in Chapter 3 would not have been possible without the University Lutheran Church at Northwestern Reverend Lloyd R Kittlaus provided me with virtually unlimited ac cess to the property to deploy and test the wireless sensor hardware in a real occupied envi ronment to which I could walk from my office in no more than five minutes I would also like to thank Aaron Miller and Amanda
157. st not contaminate the output signal of its attached sensor 3 Its trigger threshold must be predictable and repeatable 4 It must wake up the mote in time to record the highest amplitudes of the motion of interest Each of these criteria were proven to have been met by the Shake n Wake design The results of the experiment to verify criterion 1 are detailed in Section 3 3 7 3 The rest of the results of the experimental verification are detailed in Appendix A 3 3 6 1 Geophone Selection Though the Shake n Wake will operate with any type of sensor that produces a voltage output a passive or self powered sensor is necessary to realize practical power savings A geophone a passive sensor that produces output voltage using energy imparted to it by the very motion that it measures is an ideal sensor to pair with the Shake n Wake Two geophones were experimen tally tested with the Shake n Wake a GeoSpace GS 14 L3 28 Hz 5700 geophone pictured in Figure 3 22a and a GeoSpace HS 1 LT 4 5 Hz 1250 geophone pictured in Figure 3 22b Response spectra for these geophones are supplied as Appendices B 8 and B 9 respectively 62 To maximize the signal to noise ratio of the output of the geophones shunt resistors were not installed at the geophone output terminals a b Figure 3 22 a GeoSpace GS 14 L3 geophone b GeoSpace HS 1 LT 4 5 Hz geophone McKenna 2002 showed that the dominant frequencies of the walls and
158. tallation on mechanical equipment so installation was made easier through the fabrication of an aluminum bracket that could accept the protrusion and provide a flat surface for the epoxy wall interface Figure 3 27 shows a Version 3 wireless ACM node installed on a wall with a string potentiometer over a crack and an HS 1 geophone in a mounting bracket 3 3 7 1 Software The software portion of Version 3 of the MICA2 based wireless ACM system is an extension of the software of Version 2 with two significant additions the ability to allow a hardware interrupt from an external device to bring the mote out of low power sleep mode and the ability for each mote to receive and relay commands broadcast from the base station These two new features 68 Figure 3 27 Photograph of a Version 3 wireless ACM node with string potentiometer and 5 1 geophone with mounting bracket installed on a wall allow a MICA2 mote to interact with the Shake n Wake hardware and for a user to change the Shake 7 Wake triggering threshold node sampling rates and node identification numbers while the system is deployed Implementation of Version 3 required modification and cross compilation for the UC 7420 of the xlisten and xcmd applications provided with the Crossbow MICA2 system xcmd the application that allows a PC to send commands to the wireless sensor network was modified to allow the sending of ACM related commands to modify sampling rates accelerate th
159. talled after Ozer 2005 3 3 2 Sensor Board Selection Though the MICA2 mote itself features an internal 10 bit ADC it has no ability to measure tem perature or humidity nor does it have a convenient way to physically wire a sensor into its ADC 36 note that Figure 3 4 shows screw terminals ADC connectors of any kind Additionally the use of a 10 bit ADC on a sensor with a 1 5 inch full scale range yields a maximum resolution of 1465 far too coarse for the expected crack width changes outlined in Section 2 2 The MDA300CA sensor board solves all of these problems The MDA300CA pictured in Figure 3 6 is a general purpose measurement device that can be integrated with a MICA2 mote It is designed to be used in applications that re quire low frequency measurements for agricultural monitoring and environmental controls The MDA300CA adds significant sensor functionality to the MICA2 board such as a higher reso lution ADC and precision sensor excitation Figure 3 6 Photograph of a Crossbow MDA300 with quarter for scale after Dowding et al 2007 In addition to its ability to measure ambient temperature and humidity without any addi tional hardware the MDA300CA provides two additional capabilities 37 3 3 2 1 Precision Sensor Excitation Because the string potentiometer is a ratiometric sensor its output is linearly proportional to its input at any given instant In order to record a precise and acc
160. te a warranty Form No EBC 4201P Page 2 of 2 145 8 GS 14 Data Sheet SENSING SYSTEMS ENGINEERING PRODUCT CUSTOMER SPECIFICATIONS FOR GS 14 L3 28 HZ 570 OHMS 0 180 P N 146 146 GEOPHONE SPECIFICATIONS mover 99714 13 Bz ORIENTATION OPERATES IN ANY POS PART NUMBER __ 41065 570 DESCRIPTION _ SPECIFICATION _ TOLERANCE NATURAL FREQUENCY Fn 28 Hz t sg TILT ANGLE MEASURED FROM Degrees FREQUENCY TOLERANCE WITH TILT Hz COIL RESISTANCE 25 C Rc 570 0 5 vs MiRINSIC VOLTAGE SENSITIVITY G 29 V in sec 215 z 11 _v cm sec 215 NORMALIZED TRANSDUCTION CONSTANT V IN SEC 02 Rc OPEN CIRCUIT DAMPING Bo 18 30 1 DAMPING CONSTANT B R 172 MOVING MASS g 5 COIL EXCURSION _ 09 in 223 OPERATING TEMPERATURE 40 4158 40 470 c STORAGE TEMPERATURE 2160 1850 p 51 485 DIMENSIONS case HEIGHT 68 in 1 73 HEIGHT WITH TERMINALS NUN INNEREN CIC m DIAMETER 66 1 68 WEIGHT 67 oz 19 g EEUSPAEE e o s 147 2001 008 009 TVJILINJ JO X gp9NIdWVd LINIYID 33S NI N B2 ALIAILISNSS JISNIMINI 3 LY SHHU grg 3JNViSISSN 3 d H gg _ IYYNLYN oi2313 1 59 SdAL AINANDAYNA SA LNdLNO HANNS 35504534 0193130 JIWSISS BE SWH
161. ted a in the basement b on the sun porch c in the apartment and d over the garage 52 A typical mote in a plastic container 22 string potentiometer measuring the expansion and contraction of plastic donut 53 Plot of each mote s battery voltage versus time 54 Plot of temperature versus donut expansion over a period of a 200 days and b one week 56 Plot of each Version 2 wireless ACM mote s temperature versus time 57 Plot of each Version 2 wireless ACM mote s humidity versus time 57 Plot of each Version 2 wireless ACM mote s parent versus time 58 Traditional wired ACM system s determination of threshold crossing 60 a GeoSpace GS 14 L3 geophone b GeoSpace HS 1 LT 4 5 Hz geophone 62 The Shake n Wake sensor board after Jevtic et al 2007a 64 Simplified Shake n Wake reference circuit diagram 65 Photograph of a Version 3 wireless ACM node 66 xvili 3 26 3 27 3 28 3 29 3 30 3 31 3 32 3 99 3 34 Photograph of the base station of Version 3 of the wireless ACM system including UC 7420 MIB510CA cellular router power distributor and industrially rated housing Photograph of a Version 3 wireless ACM node with string potentiometer and HS 1 geophone with mounting bracket installed on a wall Current draw of a wireless ACM Version 2 mote with no Shake n Wake after Dowding et al 2007 b Version 3 mote with Shake n Wake Layout of nodes in Version 3 test deployment Ve
162. termination by sampling continuously the output of a geophone at a high frequency typically one thousand times per second and comparing the sampled value to a predetermined threshold value Should the sampled value exceed the trig ger threshold the ACM system begins recording at one thousand samples per second from the geophone and all crack displacement sensors Figure 3 21 shows this process Threshold Not Exceeded Threshold Exceeded Figure 3 21 Traditional wired ACM system s determination of threshold crossing This process of continuous digital comparison while possible to implement using a wire less sensor network is not practical if the system is to operate for months without replacing or recharging its batteries The continuous process of sampling converting the signal to a digital value and comparing that signal with a stored threshold value requires constant attention from 61 the control processor signal conditioners and analog to digital conversion circuitry Imple mentation of Mode 2 recording with a WSN therefore required the design and fabrication of a new hardware device to process the input from a geophone and determine whether or not it has detected an event of interest all without overtaxing the limited energy supply of a typical mote This new hardware device Shake n Wake was conceived with the following design criteria 1 It must not significantly increase the power consumption of a mote 2 It mu
163. tes over 20 feet in length must be inspected at least once every two years by specially trained bridge inspectors This inspection frequency can be increased based on the design past performance or age of the bridge A key part of these routine bridge inspections is identification of fatigue cracks or cracks due to cyclic loading in steel bridge members These cracks tend to grow slowly over time depending on the volume of truck traffic load history weld quality and ambient temperature United States Department of Transportation Federal Highway Administration 2006 Fatigue cracks are commonly cataloged by recording the method by which they were dis covered date of discovery crack dimensions current weather conditions presence of corrosion and other factors that may contribute to the form or behavior of the crack The BIRM indicates that the inspector should Label the member using paint or other permanent markings mark the ends of the crack the date compare to any previous markings be sensitive to aesthetics at prominent areas Photograph and sketch the member and the defect Figure 4 2 shows an example from the BIRM of how a fatigue crack should be marked 85 Figure 4 1 Fatigue crack at coped top flange of riveted connection after United States Depart ment of Transportation Federal Highway Administration 2006 Figure 4 2 Fatigue crack marked as per the BIRM after United States Department of Trans portation F
164. this reason remote reconfiguration of the triggering threshold is critical for any ACM system The best practice is to set the threshold relatively low during system installation and testing Should that threshold prove to generate too much data or record events of little interest the threshold is then slowly raised until an adequate balance is reached 19 This high frequency randomly occurring remotely configurable monitoring of both geo phones and crack sensors is known as Mode 2 logging and is more complex to implement than Mode 1 It should be noted that readings from temperature and humidity gages are ignored in Mode 2 as high frequency sampling of their data yields no useful physical information 20 2 4 2 Crack Extension Monitoring Though ACM systems focus on measuring changes in the width of the cracks under the assump tion that crack extension cannot occur without crack widening crack propagation sensors allow for direct measurement of the extension of a crack Crack propagation sensors are generally made up of a series of metallic traces of known electrical resistance A sensor can be affixed to the tip of a crack such that if the crack propagates one or more of the metallic traces will break which will change the resistance measured across the terminals of the sensor Figure 2 9 shows how such a sensor might function e of propageton B Figure 2 9 Resistance measured between points A and B dec
165. tion to wireless ACM is quality of the sensor excitation and analog to digital conversion capabilities of the motes In a state of the art wired ACM system power is supplied to the sensors by an independent 15 V DC regulated power supply capable of supplying 0 3 A of regulated current and powered by standard 110 V AC SOLA HD 2009 Analog to digital conversion in the state of the art wired ACM system is performed by a 16 bit analog to digital converter ADC with software configurable gain to allow for maximum use of the 16 bit resolution over the expected output range of the sensor SoMat Inc 2010 The wireless ACM systems examined in this chapter have far less sophisticated power supplies and ADC units extra effort is required to achieve the repeatable high precision high frequency measurements required by ACM In some cases a single WSN cannot meet all of these requirements in addition to the requirement of a six month operational lifetime with no human interaction Additionally physical robustness of a wireless ACM system is not guaranteed it depends completely on the manufacturer and model of the WSN upon which the wireless ACM system is built In the case of certain types of WSNs the end user is responsible for fabricating an enclosure to protect the delicate electronics of the system components Finally and perhaps most importantly few commercially available WSNs are designed for end user deployment especially end users who
166. tions Document Part Number 6020 0049 05 Rev A Web www xbow com 140 Specifications Remarks STARGATE Processor Board Intel PXA255 Xscale Intel SA1111 StrongARM Memory 64 MB SDRAM 32 MB FLASH Communications PCMCIA Slot Compact Flash Slot 51 pin GPIO Optional I2C Port Optional Serial Port 2 General Processor Board Top Li lon Battery Option Watch Dog Timer WDT Battery Gas Gauge LED and User Application Switch Power Switch STARGATE Daughter Card Communications 10 Base T Ethernet Port RS 232 Serial Port JTAG Debug Port USB Host Port Daughter Card General Power Adaptor Reset Button Real Time Clock Physical Processor Board in cm Weight gt Daughter Card in Stargate Block Diagram cm Weight oz 9 Environmental Stargate Kit Contents Operating Temperature Specifications subject to change without notice CD ROM Contents Ordering Information Model Description SPB400CB Stargate Processor Board Document Part Number 6020 0049 05 Rev A Crossbow Technology Inc 4145 North First Street San Jose California 95134 141 B 6 Alkaline Battery Data Sheet PRODUCT DATASHEET Energizer 1 800 3
167. to extend system longevity Instead the design of a wireless 28 Figure 3 1 Example of a multi hop network green lines represent reliable radio links between motes after Crossbow Technology Inc 2009b ACM system s hardware and software must prioritize minimization of size but maximization of system longevity using an energy source no larger than 2 3 standard AA batteries The second and relatively obvious challenge is that due to the fact that motes run on batter ies it is impractical to continuously buffer data in order to monitor the readings from sensors before a significant sensor reading triggers the system to record at a high frequency Since there is no way to know in advance when such a sensor reading will be needed it becomes necessary to continuously check the data against a known threshold This continuous sample compare buffer discard cycle utilized by traditional ACM systems is impractical for any system based 29 on a WSN since WSNs achieve their longevity by sleeping or operating in an extremely low power mode for the large majority of their deployed life In this sleeping mode sensors cannot be read radio signals cannot be sent or received and each mote is powered off with the exception of a low power timer that instructs it when to wake up or resume a fully functional operating state in order to take its next scheduled reading The third and somewhat less obvious challenge inherent to the transi
168. to steel bridges to track progression of existing cracks 2 4 2 2 Custom Crack Propagation Patterns To overcome the two main difficulties inherent in using a commercially available crack propa gation sensor for either an ACM system or a system designed to measure cracks in steel a new type of crack propagation sensor is proposed in this thesis a custom crack propagation pattern This pattern detailed in Chapter 4 can be made in whatever shape is necessary for capturing any possible direction of crack growth It also uses the wall or steel to which it is mounted as its substrate so the problem of mismatched material strengths between the substrate and the sensor backing is eliminated 22 Figure 2 10 Two types of commercially available crack propagation patterns shown with a quarter for scale 2 5 Examples of the output of an ACM system The following images are taken from the live Web interface of an ACM system Figure 2 shows the long term correlation between humidity and crack displacement as captured with Mode 1 recording Figure 2 11b shows typically recorded crack displacement waveforms during a dynamically triggered event as captured with Mode 2 recording Outdoor Humidity RH 1005 904 804 NE nF gt FE 604 2 gt 504 7 404 wet s 304 Eo cT 204 DH 104 41 4 2 AG 44 45 46 4 Exterior Crack icroinches 403007 35 0004 30 000
169. traces from the conductive steel substrate Sherwin Williams MACROPOXY 646 Fast Cure Epoxy paint was chosen to most closely simulate existing bridge paint Hopwood 2008 Industrially rated quick setting epoxy adhesive was used to affix the bus resistors to the steel before application of the conductive traces Sensor application was performed at room temperature Figure 4 19 shows an engineer applying the gage to a test coupon 4 3 3 Proof of Concept Experiment A single A36 steel coupon identical to the coupons used in the experiments in Section 4 2 2 was painted with the simulated bridge paint Two custom crack propagation sensors were then affixed to the coupon one on either side Figure 4 20 shows the test coupon with a custom crack propagation gage installed Because of the small size of the coupon relative to the size of the sensor not all pairs of terminals were connected with conductive paint As such it was expected that the output of the sensor would behave as though it started with several rungs broken 104 Figure 4 19 Photograph of an engineer applying a custom crack propagation gage Figure 4 20 Photograph of coupon with attached custom crack propagation gage 105 The experimental procedure to test the custom crack propagation gage was also identical to the one detailed in Section 4 2 2 The coupon was fatigued with no sensors or paint until the crack propagation was initiated Then cyclic tension between 0 07 kip
170. ttings for mesh formation are used set quick X If X is 1 the motes will transmit mesh formation information much more quickly allowing a mesh to me be formed quickly X is an integer 1 31 set pot X X 1 15 the most sensitive Table 3 2 ACM related commands added to xcmd by Version 3 of the MICA2 based wireless ACM software 3 3 7 3 Analysis of Power Consumption To analyze the power consumption of a Shake n Wake enabled mote the simple ammeter circuit and calculations described in Section 3 3 5 3 were utilized Figure 3 28 shows the current draw of a mote with Shake n Wake installed as compared with a Version 2 mote Figure 3 28b clearly indicates that during the crucial sleep state of the mote the current draw varies between 0 03 and 0 05 milliamps very similar to the sleep mode current draw of the Version 2 wireless 71 ACM system without Shake n Wake shown in Figure 3 28a Thus it can be concluded that the Shake n Wake does not draw a significant amount of additional power 1 Sampling Listening and or transmission 5 e E ROI N gt i500 Time seca a Sampling and 7 Radio Transmission gt 9 15m A Radio Receive for Mesh Maintenance 2 6 Heartbeat Low Power Sleep 1 2mA 0 030 0 050 Current mA 0 Li L uL AU I UE 200 220 240 260 280 300 Time seconds b
171. ues can be applied to any structure that exhibits cracking over time the primary motivation in the development of this technique is to supplement the in service inspection of fatigue cracks in steel bridges Fatigue cracks in steel such as those shown in Figure 4 1 tend to grow slowly over time and when found during routine inspection of steel bridges are cataloged according to procedures laid out in the Bridge Inspector s Reference Manual or BIRM United States Department of Transportation Federal Highway Administra tion 2006 These cracks are then re examined at the next inspection and compared to records to determine whether the crack has grown ACPS especially on bridges is an ideal application for a wireless sensor network Run ning wires across bridges between different points of interest is usually cost prohibitive and is 84 often impossible due to superstructure configuration and access restrictions Since access can be difficult and expensive it is desirable to minimize installation time and maximize time be tween maintenance visits so long lasting solar powered nodes are ideal Furthermore power management strategies implemented by the manufacturers of existing wireless sensor networks are well suited to the low sampling rate required by ACPS 4 1 1 Visual Inspection Visual inspection is the most common mechanism by which the growth of cracks is recorded quantitatively By federal law every bridge in the United Sta
172. urate reading from such a sensor the data logger must either record simultaneously the input to and the output from the potentiometer or provide as an input to the potentiometer a precisely regulated voltage that is guaranteed to be constant at a known value whenever the sensor is read The MDA300CA does the latter by providing a 2 5 V DC regulated excitation voltage to the potentiometer 3 3 2 2 Precision Differential Channels with 12 bit ADC The MDA300CA has several different channels with which it can read analog signals with 12 bit resolution four times more resolution than the MICA2 s internal ADC Four of the MDA300CA s channels are precision differential channels with a sensor front end gain of 100 which yields an input range of 12 5 mV with a constant programmable offset such that a sensor with a minimum output of 0 V DC can still take advantage of the full 25 mV range With a 2 5 volt precision excitation and the front end gain the MDA300CA is capable of resolving 0 0061 millivolts or approximately 3 7 of displacement using the string potentiometer This is within the specification laid out in Section 2 2 The active sensor range of the potentiometer in the 25 mV window is 15 000 30 of the range of the eddy current gages used in the traditional wired ACM systems see Table 2 1 but still acceptable for ACM Ozer 2005 It is important to note that although the MDA300CA is theoretically capable of resolving 3 7 pin of
173. using secure shell and issues a command to the network to enter quick mesh mode in which the rate of packet transmission is significantly increased such that a mesh network forms in under one minute instead of in 30 40 minutes The engineer uses the xlisten program on the UC 7420 to monitor the network output until he sees that all sensors have acknowledged receipt of the quick mesh command then he issues another command to disable quick mesh mode He then chooses a mote issues a command to that mote to sample once per second and uses the increased sampling rate and his computer to center the string potentiometer in the middle of its active range He then decreases the sample rate of that mote and moves on to the next node until all potentiometers are centered 70 When the motes are first powered on the trigger threshold on each Shake n Wake is set by default to 31 the least sensitive setting By issuing a command from the base station either at install time or at any later time by connecting to the base station over the Internet the trigger threshold may be adjusted to suit the needs of the site Table 3 2 details the ACM related commands that are made available with Version 3 of the MICA2 based wireless ACM software X is an integer 1 30 set X specifies frequency in seconds of ticks X is an integer 1 200 set ticks X A sample is taken every X ticks X is either O or 1 If X is 0 the default se
174. ve Paint TX 5 lt gt x ox SO x 2 LXXX X OX OX TERS gt 5 gt 27 x e 5 6 0600 0 Resistors of Known Value Figure 4 16 Schematic of a custom crack propagation gage crack grows to the right 3 V DC is applied between A and B sensor output is measured between C and B the common pin The measured resistance between each of the other nine pins and the common pin is always identical regardless of what is connected or not connected to any of the other pins This resistor configuration is ideal to simplify fabrication and deployment of a custom crack propagation sensor Figure 4 17 Photograph of a commercially available bus resistor after Bourns 2006 101 The values of the bus resistors and the current sense resistor must be selected such that each rung break my be reliably detected by an mote s 10 bit analog to digital converter and 3 V DC precision excitation voltage Because the combined resistance of resistors wired in parallel is equal to the reciprocal of the sum of the reciprocals of each resistors value the change in resistance of the entire sensor will be smallest for the first rung break and increase non linearly for each subsequent rung break The change in resistance and therefore voltage output for the first rung break must be max
175. y 30 i Y n 20 5 1 1 1 1 10 1 1 1 0 20 40 60 80 100 120 140 160 0 20 40 60 80 100 120 140 160 Days Deployed Days Deployed Battery vs Days Deployed Parent vs Days Deployed tery vs Days Deploy ys Deploy 3500 Mote 3 Mote 3 Mote 4 Mote 4 1 n 3000 Y 7 2500 H gh m a Pc 15004 1000 H 4 1 f 500 H 2 0 1 1 1 1 1 1 1 1 1 1 0 20 40 60 80 100 120 140 160 0 20 60 80 100 120 140 160 Days Deployed Days Deployed Figure 3 31 Plots of a temperature b humidity c battery voltage and d parent mote ad dress recorded by Version 3 of the wireless ACM system over the entire deploy ment period Figure 3 32 shows the data recorded over the period from day 75 when the base station workarund was implemented through the time the system was removed from the test structure Figure 3 32d shows when a Shake n Wake trigger signal was received at Motes 3 or 4 76 Temperature vs Days Deployed Humidity vs Days Deployed 30 55 Mole 3 Mote 4 50 25 45 40 S FEE 5 R E E 3 E E 3H 5 15 b 5 25 20 10 15 5 1 1 1 1 1 10 1 1 1 1 1 80 90 100 120 130 140 150 80 90 100 110 120 130 140 150 Days Deployed Days Deployed Motes 3 and 4 Crack Expansion vs Days Deployed Impacts vs Days Deployed 3000 Mote 3 Mote 3 Mote 4 Mote 4 2000 4 AR
176. y fabricated alu minum mounting accessories The first a square aluminum plate with countersunk holes is screwed into the bottom of the string potentiometer then glued to a wall on one side of a crack The plate prevents epoxy from entering the housing of the potentiometer It also provides a 33 uniform gluing surface to ensure robust installation The second part of the mounting fixture a small aluminum block with two drilled and tapped holes to accept a very thin aluminum plate with two corresponding holes is glued to the opposite side of the crack from the potentiometer and grasps the measurement string The block is sized such that the string remains parallel to the wall This type of fixture is preferable to a hook or a post because there is no possibility for the string to slip or turn Figure 3 3 shows a fully mounted string potentiometer SG LOCO NS LO 051 Figure 3 3 Photograph of a fully mounted string potentiometer after Ozer 2005 3 3 WSN Selection The WSN platform selected for the initial migration of ACM to the wireless domain was the MICA2 wireless sensor network manufactured and sold by by Crossbow Technology Inc and powered by TinyOS 1 x software The MICA2 system s small size flexible software ability to operate without a PC on site large user base relatively low cost and a catalog of add on sensor 34 boards made it the ideal choice to begin to develop wireless ACM system Figure 3
177. y of the sensor or the existence of the crack sensor might actually affect the movement of the crack Other sensors do not physically bridge the crack Sensor size the need for signal conditioning electronics and cost all play a role in determining the optimal sensor for an ACM system 11 The ACM strategy of measuring the changes in the widths of cracks to characterize crack response to weather and vibration makes the assumption that the crack moves with a single degree of freedom opening and closing along a line perpendicular to the crack i e along direction A in Figure 2 5 Experience reveals however that cracks will respond to excitation not only by opening and closing but also by their individual sides moving relative to each other in a directional normal to the plane of the wall in which the crack exists This motion known as out of plane movement and shown as direction C in Figure 2 5 is generally not significant in the characterization of crack response Waldron 2006 but can have a significant impact on the proper functionality of crack width displacement sensors For example should significant motion occur in directions B or C in a crack that is monitored by the core of the LVDT may be forced into the side of the sensor casing causing stick slip behavior or even complete sensor failure This danger can be circumvented using an eddy current gage A in plane parallel B in plane perpendicular C out o

Wireless Sensor Networks for Monitoring Cracks in Structures

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