cio-exp-bridge16 - OMEGA Engineering
Contents
1. 12 5 3 1 Selecting the Power Source for the Board 12 5 3 2 Selecting the Power Source for the Excitation Voltage 12 5 3 3 Selecting the Excitation Voltage 2i eio tex ibn preme oor ces e ders 13 5 4 Determining the Appropriate Gain 14 RR TTA the ETT TTT 14 K Serene Board TTT SOE abet ok ew iab LR pet 14 5 3 2 Setting Channel GaN oes ui eee edo caca e ace dp e eae tem aa dR Z 15 5 6 Configuring the Bridge ero E RE CUR E 16 5 6 1 Bridge Completion Resistors ssl sente nanas ne items 16 5 6 2 Nulling Potentiometers amp Arm Resistor 17 5 6 3 Strain Gauge Bridge Configuration Examples 17 GSPECIEICATIONS 5 N Sa e o Re RO Rh cec Rl GE RR TREE es 21 TAPPENDIX roii Me BOREL er BRE ONERE VERE OP Rt ANAT ey EOE Rate Me gode 23 KON About SCAM GAUGES L2 cce Saa Mead WW EVER ERR EP Oma bea ke es ingre 23 PALIN hat Are tran Gauges in Le A ne ln he ult ddeRd 23 7 1 2 Specification of Strain Gauges i465 64445 einen HORE VENE uen ee 23 7 2 Reference Material for Application of Strain Gauges 23 1 INTRODUCTION The CIO EXP BRIDGE16 is a signal conditioning accessory designed for use with the DASOS and DAS16 family of data acquisition boards The CIO EXP BRIDGE16 contains circuitry to condition strain gauge sensors on a per channel basis2. gt gt Figure 5 2 shows the switch and the excitation power source jumper set for the factory defaults Excitation is set for 10V ON Power source must be set to 12V as shown in Figure 5 1 or PEXT S17 Do not select an excitation voltage at the switch that exceeds the excitation power supply voltage AOI un Q o E T Figure 5 2 Excitation Voltage Select Switches 13 5 4 Determining the Appropriate Gain To accurately measure a voltage the full scale of the signal should be matched to the full range of the input circuit Most DAS boards have an input range of 5V which is the native range of the analog to digital converter at the heart of the board Some DAS boards include amplification on the input circuit to allow the signal to be amplified to make better use of the resolution of the A D For example an input signal which varies between O and 1 volt would only be using 1 10th of a 5V A D converter s resolution By switching the input signal of the DAS board to unipolar no negative voltage and amplifying the sign wave signal by 5 the entire range of the A D converter is used and a higher resolution measurement may be made By adding this gain and selecting this range the resolution on a 12 bit A D improves from 2 4 millivolts per bit to 0 24 millivolts per bit If you needed to measure a change of 1 millivolt you would need an amplification of 10 In order to match your signals with the inpu
3. When all are low CURT M e ED aap the mux is set to Input 0 The lines are binary Mure URS W e D coded where MUXADDRI is the LSB and MA EM we MUXADDRA is the MSB UU 5 MEM MUX ADDR 1 o A jumper CH SEL selects which output channel c 56 e is read by the DASO8 or DASI6 board nc 5 e OBS e i o e 21 NC NC 2 e x 1 e J 20 NC 1 z Pp Figure 3 4 37 Pin Output Connector Pinout 3 5 Powering The CIO EXP BRIDGE16 The CIO EXP BRIDGE16 can be powered through the 37 pin cable the power screw terminal or the Molex connector The power that can be carried through the 37 pin connector is limited so we recommend using this source only when a single CIO EXP BRIDGE16 is used The power required to run a CIO EXP BRIDGE16 is dependent on the board configuration Remember that additional power will be drawn when the CIO EXP BRIDGEI16 is configured for resistance measurement bridge configuration due to the current required for each bridge 3 5 1 Power Source Switch One of the switches on the eight position DIP switch S17 X near the output channel jumpers controls the source of the 5V power to the CIO EXP BRIDGE16 Shown in Figure EE Z M Og u HTI LX IN398 3 5 itis the 3rd switch from the left When positioned down ON 5 COMP 5V power is drawn from the personal computer through the signal cable When positioned up OFF REM 5V power is taken from the optional external 5V power connector the
4. 15V external source 10 VEXC Miscellaneous Environmental Operating temperature range Storage temperature range Humidity OP07 1 10V 5 mA 25 mA indefinite DC 100 Ohms max Output jumper selectable for one of 16 channels P1 amp P2 Output to Output 15 HI508A multiplexer 2N2222 transistor inverter 4 digital inputs for selecting multiplexer channel 0 8V max AV absolute min 1 0V max 4V absolute min 2 4V min 9V absolute max 1 27V min 9V absolute max 10V 4V 2V 1V 0 5V 5V from PC 5V from MOLEX 12V from PC external PEXT screw terminal 333mA 833mA 1333mA Output jumper selectable for one of 16 channels P1 amp P2 Output to Output 15 Voltage adjustable for zero error 0 to 60 C 40 to 100 C 0 to 90 non condensing 22 7 APPENDIX 7 1 About Strain Gauges 7 1 1 What Are Strain Gauges A Strain Gauge is a variable resistance device whose resistance changes in proportion to the amount it is stretched or compressed Physically it is an etched metal foil in a grid pattern that is glued to any surface which undergoes strain The output is a dimensionless quantity defined as change in length and whose symbol is A micro strain of 1 means that length of the surface of interest has changed by ppm The ratio of resistance change to strain change is known as the Gauge Factor GF Typical metal foil strain gauges have Gauge Factors of 2 to 2 1 This means that the resistance will
5. CIO EXP BRIDGE16 Boards 6 3 7 Connecting a Test Voltage 4 socios Ace he ad RERO NU REY RE RE REN 6 3 8 Verifying The Installation 6 4 CONFIGURATION FOR VOLTAGE MEASUREMENT 7 4 1 Channel Selection 1555 exo aX a Cea Neg codo a dela a e erage ats 7 4 2 Powering the CIO EXP BRIDGEIG6 7 4 3 Determining The Appropriate Gain 7 Semma the Gait 5 seb bes gp AR N Pistes Ae S saei ue RR a 8 Al Setung Bodrd GAN genta pa EXE TRA bee ORI m RATRE lad A Ay 8 4 4 2 Setting Channel Gain 5 en ee X Rh aE e SUR E REX STA RE RE RAS 9 4 5 Aftenuatiol osos rente MENORES Eau Rae MGV SR NOS Radek COR tant 10 4 6 Connecting Voltage Signals 10 AG Single L oon nt ci bes er el bIREREARIA PRA EEEUMRRAE ENDLIM EIE ee ee Eke 11 4 6 2 Floating Differential 45 sce er RR ERR RU ERR ORE VER SUE d ER VAR 11 4 6 3 Eully Differential 5 4 m Lebe rs doe SR d o ie Pis Lo ade a e d a 11 4 7 Verifying the Installation 11 5 CONFIGURATION FOR RESISTANCE MEASUREMENT 12 5 4 Channel Select 4 etes epe b RO Id T E end ERU A Re As 12 5 2 VEXC Jumper Select o en Bes BS Ete REQUE We RAS C ELE eR bae 12 5 3 Powering The CIO EXP BRIDGE16
6. OTHERS TO BE OFF UP Figure 4 2 Input Channel Gain Select Switch Typ Table 4 1 Resistor Positions for User Selected Gains Channel Resistor Position Channel Resistor Position 0 RX100 8 RX108 1 RX101 9 RX109 2 RX102 10 RX110 3 RX103 11 RXIII 4 RX104 12 RX112 5 RX105 13 RX113 6 RX106 14 RX114 7 RX107 15 RX115 Gain Resistor Value 100 364 Ohms 200 161 Ohms 500 40 Ohms 700 17 Ohms 800 10 Ohms The equation for selecting the USER gain resistor is Ruser 40000 Gain 1 40 Amplifying a signal on one channel will not affect readings on another channel 4 5 Attenuation If your signal is in a range greater than the full scale range of the A D you must either set the A D for a higher full scale range if available or divide attenuate the signal until the result is less than or equal to the A D s full scale range This section describes signal attenuation INPUT A voltage divider is constructed from a pair of il precision resistors selected according to the Ra equation Volts In L OUT Attenuation A Ra Rb Rb See Figure 4 3 at right for the schematic of a Rb je Divided voltage divider v PC GROUND PC GROUND Figure 4 3 Voltage Divider For example if your signal is 0 to 10V it must be attenuated to 5V max for an attenuation of 2 1 or simply 2 Using 10k resistors 2 10K 10K 10K For any attenuation pick a s
7. and convert the sensor s output to a voltage suitable for conversion by a DASOS or other analog to digital conversion board This manual is organized into sections that explain the CIO EXP BRIDGE 06 as follows Software Installation All users should review this section regardless of the application General Configuration All users should review this section regardless of the application Configuration for Voltage Measurement Users interested in voltage measurement applications should review this section Configuration for Resistance Measurement Users interested in resistance or strain gauge measurement applications should review this section Please read the manual carefully There are many optional resistors jumpers and other connections to be made on the CIO EXP BRIDGE16 Failure to set up the channels correctly will frustrate you with inaccurate measurements 2 SOFTWARE INSTALLATION Software is not included with the CIO EXP BRIDGE16 but each of the data acquisition boards with which it is intended to be used includes software called InstaCal that may be used to aid installation verify operation and perform calibration of the CIO EXP BRIDGE16 The disk or CD labeled InstaCal contains this software package If you ordered the Universal Library you should load nstaCal from that CD or disk set The board has a variety of switches and jumpers to set before installing the board in your computer InstaCal will show you all avai
8. bridge voltage is Vor 10V 350 700 350 350 350 0V After a downward force is applied Vor 10V 350 700 350 350 350 175 Vor 1 25mV 18 Choosing an amplifier gain of X1000 results in 1 25V maximum presented to the DAS board Choosing an additional X2 5 overall output gain results in a total gain of 2500 thus sending 3 125V maximum to the DAS board This makes an optimum use of the 5V unipolar range A Half Bridge Example For a 4 bridge circuit Figure 5 7 the strain gauge has two resistive elements which are connected across two legs of the bridge The two legs would always be A amp C or B amp D The other two legs of the bridge must be populated with the precision 350 ohm completion resistors EXCITATION VOLTS A SENSE LOW EXCITATION VOLTS EXCITATION VOLAGE Null Pot SENSE HIGH TO CHANNEL MULTIPLEXOR Pass Filter Figure 5 7 42 Bridge Circuit Simplified Schematic Half Bridge Calculations The 42 bridge implementation consists of two strain gauges one on the top of the beam as in the 4 bridge example and one on the bottom of the beam The strain gauge on the bottom of the beam replaces completion resistor C in the 4 bridge implementation Two active strain gauge elements one in tension and one in compression result in twice the sensitivity of the 4 bridge One element increases resistance while the second element decreases resistan
9. effect of this switch is multiplicative with respect to the individual channel gains For example if you have set an input channel gain to X100 and the board output gain to X2 5 the signal is amplified by 250 before it reaches the A D board 14 5 5 Setting Channel Gain There is a gain switch for each channel Figure 5 4 Set the input channel gain to match the expected voltage output of the bridge you are measuring to the input range of the A D board as described above Channel Gain Switch Select a gain higher than unity by moving the switch for that gain down All other switches should be left in the UP position A custom gain may be selected on the CIO EXP BRIDGE16 by installing a precision resistor and setting the switch marked U User in the down position See Table 5 1 below for positions and some sample gain values CHO G x ox o coo oc c GAIN SWITCHES FOR CHANNEL 0 SET FOR A GAIN OF 10 PUSH SLIDER TO ON DOWN TO SELECT GAIN ALL OTHERS TO BE OFF UP Figure 5 4 Input Channel Gain Switches Table 5 1 User Specified Gain Resistor Positions Channel Resistor Position Channel Resistor Position 0 RX100 8 RX108 1 RX101 9 RX109 2 RX102 10 RX110 3 RX103 11 RXIII 4 RX104 12 RX112 5 RX105 13 RX113 6 RX106 14 RX114 7 RX107 15 RX115 Gain Resistor Value 100 364 Ohms 200 161 Ohms 300 130 Ohms 500 40 Ohms 700 17 Ohm
10. measure the signal EXAMPLE A laboratory instrument with its own wall plug Sometimes there is a voltage between wall outlet grounds 4 7 Verifying the Installation To verify the installation use the InstaCal program installed on your computer This software came with your A D board if you bought the board from the same manufacturer as the CIO EXP BRIDGE16 If your A D board is not from the same manufacturer but is compatible please call technical support and request a copy of InstaCal Use InstaCal s TEST option to verify that a signal present at one of the CIO EXP BRIDGE16 inputs can be read When using an AC signal source keep the frequency below 70Hz to avoid attenuation by the low pass filter 11 5 CONFIGURATION FOR RESISTANCE MEASUREMENT Resistance measurements are made using the CIO EXP BRIDGEI6 by constructing a resistor bridge containing known resistor values that are to be compared to the resistor value to be measured This is known as a Wheatstone Bridge The typical application is a strain gauge Strain gauge sensors are variable resistance devices When installed in one leg of the resistor bridge as the unknown resistor their value can be measured The Wheatstone Bridge circuit is extremely sensitive to changes in resistance in one leg relative to the others There are various types of bridge sensors but the descriptions and examples here are for strain gauges 5 1 Channel Select The General Configurati
11. the bottom Their resistance decreases under the resultant compression but bridge voltage increases Gauge resistors D and A are on the top of the beam Their resistance increases under the resultant tension and bridge voltage likewise increases equal in magnitude to the changes in D and A Vor 10V 350 0 175 350 0 175 350 0 175 350 0 175 350 0 175 350 0 175 Vor 10V 350 0 175 700 349 825 700 Vir 5 00mV Choosing a gain of X1000 presents 5V to the DAS board covering its entire 5V unipolar range An excitation voltage of 4V could be been used in combination with a gain of 2500 X1000 on the input channel and X2 5 on the output This would also result in 5V to the DAS board The advantage to using a lower excitation voltage is that it causes less power dissipation on the strain gauge element itself reducing thermal expansion from self heating 20 Power consumption 5V excludes any power to bridges Analog input section Input amplifier type Number of channels Gains Gain Error Gain 1 2 5 Gain 10 25 Gain 100 250 Gain 1000 2500 Linearity Gain 1 2 5 Gain 10 25 Gain 100 250 Gain 1000 2500 Input Offset Gain TC Gain Gain 100 Gain 1000 Input Offset TC Gain 1 2 5 Gain 10 25 Gain 100 250 Gain 1000 2500 Common Mode Range CMRR 6 SPECIFICATIONS 250mA typical 350mA maximum INA102 16 di
12. verifying the installation and operation of the CIO EXP BRIDGEI6 with your data acquisition board Configure your boards as described in that section before continuing with this section 4 3 Determining The Appropriate Gain To accurately measure a voltage the full scale of the signal should be matched to the full range of the input circuit Most DAS boards have an input range of 5V which is the native range of the analog to digital converter at the heart of the board Some DAS boards include amplification on the input circuit to allow the signal to be amplified to make better use of the resolution of the A D For example an input signal which varies between 0 and 1 volt would only be using 1 10th of a 5V A D converter s resolution By switching the input signal of the DAS board to unipolar no negative voltage and amplifying the input signal by 5 the entire range of the A D converter is used and a higher resolution measurement may be made By adding this gain and selecting this range the resolution on a 12 bit A D improves from 2 4 millivolts per bit to 0 24 millivolts per bit If you needed to measure a change of 1 millivolt you would need an amplification of 10 In order to match your signals with the input range of the A D board you should do a similar calculation and set switches on the CIO EXP BRIDGE16 for the required gain Remember to make sure that the settings in InstaCal match the switches on the DAS and CIO EXP BRIDGE16 boards
13. 1000 A user specified gain may be set by supplying a precision resistor at position RX and setting the U option on switch CH to ON 4 4 1 Setting Board Gain There is a switch on DIP switch block S17 labeled X1 and X2 5 Sliding this switch down amplifies the output of the multiplexers by 2 5 The factory default position up has a gain of 1 unity Refer to Figure 4 1 The X2 5 gain switch is useful in some voltage and bridge measurements If you desire a voltage gain of 2 5 25 250 or 2500 set this switch down Figure 4 1 Board Output Gain Switch Location For voltage measurements a gain of 2500 is very high and will reduce your signal to noise ratio The effect of this switch is multiplicative with respect to the individual channel gains For example if you have set an input channel gain to X100 and the board output gain to X2 5 the signal is amplified by 250 before it reaches the A D board 4 4 2 Setting Channel Gain Select a gain higher than unity by moving the switch for that gain down All other switches should be left in the UP position A custom gain may be selected on the CIO EXP BRIDGE16 by installing a precision resistor and setting the switch marked U User in the down position See Table 4 1 following for board positions and some sample gain values CHO C x e e o 5 000IX GAIN SWITCHES FOR CHANNEL 0 SET FOR A GAIN OF 10 PUSH SLIDER TO ON DOWN TO SELECT GAIN ALL
14. CIO EXP BRIDGE16 User s Manual Revision 2 January 2001 O Copyright 2001 OMEGA ENGINEERING INC Table of Contents LINTRODUCTION endete bor b bi be Pick ia e ps rem etia Db aoi on 1 2 SOFTWARE INSTALLATION ooo 1 3 GENERAL CONFIGURATION 2 3 1 A D Board Type Select Jumper 2 3 2 Setting The Output Channel 2 3 3 Configuring the A D Board 3 35301 DASOS Family Setup oes eedem Rb dTa ence Wo REER Ra Ra reed gata 3 3 22 DAS16 Family Setup s visae er ER ee s g HEA EE NS ee 3 3 9 9 ANAD Boards 104 etse b Ee eR ebd bte flm Mer eoe d deles 3 3 4 CONNECTING THE CIO EXP BRIDGE16 TO THE A D BOARD 4 3 4 1 Connecting to a DASOS Series A D Board 4 3 4 2 Connecting to a DAS16 Series A D Board 4 33 Other A D Boas 1c p x ea Ne RE ER ERR obe XE RR pee 4 3 5 Powering The CIO EXP BRIDGE16 4 2 2 1 Power Source SWE serant a fee bt Exp weed ente eater aera Let 5 3 5 2 Powering with the 37 pin Connector 5 3 5 3 Powering with the Molex Connector 5 3 5 4 Powering Through the Power Screw Terminals 5 3 6 Daisy Chaining
15. For more information on excitation voltages refer to the section on bridge sensors 5V Excitation Voltage Source If your choice for the excitation voltage source is 5V you may choose a 0 5V IV 2V or 4V excitation voltage for your bridge sensors The 5V option is always available since 5V is required to power the CIO EXP BRIDGE16 12V Excitation Voltage Source If your choice for the excitation voltage source is 12V PC power you have the choice of 0 5 1 2 4 or 10 volt excitation for your bridge sensors The option to power from the PC 12 volt supply exists only with DASOS family boards except that 12V is not valid with the CIO DAS08 AO or PGA PEXT Excitation Voltage Source An external power supply can be used If you choose a separate power supply it must be a floating or isolated supply one with three terminals Do not tie the GND and V terminal together Output voltage must not exceed 15V If your power supply is not floating it is likely that you will create a ground loop current flow in the ground lines A ground loop will induce an error in your reading Connect the power supply to the CIO EXP BRIDGE16 at the terminals labeled PEXT and PEXT on the screw terminal block located adjacent to the 37 pin connector P2 5 3 3 Selecting the Excitation Voltage DIP switch S17 has five switches to select bridge excitation voltage Only set one ON All others must be OFF X Ta Z Wat gt
16. If you are measuring signals greater than the maximum full scale range of the A D see the section on attenuation To choose a switch selectable amplification here are the calculations you need to perform Divide the full range selected for the A D board by the full range of the signal to be measured to determine the maximum gain of the CIO EXP board For best resolution use the highest gain possible up to the calculated maximum gain For example if the A D board is to be used at a range of 5V the full range of the board is 10 If your signal ranges between 0 5 volts and 0 5 volts the full range of the signal is 1 volt Divide 10 by 1 fora result of 10 That is the maximum gain you can use If your signal is unipolar and ranges less than 0 to 5V you would likely choose the 5V unipolar range for the A D board if available Given an input signal ranging from 0 to 0 5 volts the full range of the signal is 1 2 volt Divide 5 the full range of the A D by 0 5 the full range of the signal for a result of 10 That is the maximum gain you can use 4 4 Setting the Gain Gain amplification allows you to boost your signal to take full advantage of the resolution of the A D converter However when amplifying a signal any noise is amplified as well Amplification for ALL channels board output gain is switch selectable S17 for X1 or X2 5 Input amplification for EACH CHANNEL is switch selectable CHO through CH15 for X1 X10 X100 or X
17. Molex connector labeled P19 or the 5V screw terminal connection S17 AOI AT AT Al AS 0 un a lt YO Figure 3 5 Power Source Switch amp Jumper 3 5 2 Powering with the 37 pin Connector You can power the CIO EXP BRIDGE16 via the 37 pin cable No more than one CIO EXP BRIDGE16 should be powered using the 37 pin cable This option is not available when using some A D boards If the A D board you are using supplies 5V at pin 29 or at pin 1 when using the C EXP2DAS16 signal cable you can power the CIO EXP BRIDGE16 through the 37 pin connector by setting the power select switch on S17 to 5 COMP 3 5 3 Powering with the Molex Connector The CIO EXP BRIDGE16 can be powered off the PC s power supply by connecting the optional external 5V power connector the Molex connector labeled P19 to the PC s power supply through a C MOLEX 10 cable This cable has the same Molex connector that is used inside the PC and so can be connected directly to the PC s power supply through one of the spare connectors The cable is keyed so it should not be forced When inserted properly it will slide easily and snap in place 3 5 4 Powering Through the Power Screw Terminals A set of screw terminals labeled 5V and GND are located next to the 37 pin connector P2 You can power the CIO EXP BRIDGE16 from a 5V 5 power supply capable of at least 400 mA For this option set the power select switch on S17 to REM CAUTION Th
18. The measured voltage will increase 5 6 1 Bridge Completion Resistors You will likely have to install bridge completion resistors in the CIO EXP BRIDGE16 to match the resistance of the external gauge If you are using a 4 bridge you will need to install three precision resistors to complete the bridge If you are using a 4 bridge you will need to install two resistors to complete the bridge If you are using a full bridge there are no resistors to install 16 Referring back to Figure 5 5 the legs of the bridge are labeled A B C and D Table 5 3 below matches the legs of the bridge to the resistor number nomenclature that appears on the CIO EXP BRIDGE16 Table 5 3 Bridge Resistor Identities 0 RXI RX RX3 RX4 RX5 R6 1 RX7 RX8 RX9 RXIO RXII RD 2 RXI RXi4 RXI5 RXI6 RXI7 RI8 3 RXI9 RX20 RX21 RX22 RX23 RM 4 RX25 RX26 RX27 RX28 RX29 R30 5 RX32 RX2 RX3 RX34 RX35 R36 6 RX37 RX38 RX39 RX40 0 RX41 R2 8 RX49 RXSO RX5 RXS2 RX53 R54 9 RXSS RX56 RXS7 RX58 RX5 R to RX61 RXG RX63 RX64 RX6S R66 14 RX85 RX86 RX87 RX8S8 RX89 R90 15 RX91 RX92 RX93 RXo4 RX95 R Some values of precision resistors are available from OMEGA Engineeering Note Positions marked D1 through D64 are empty and are not used 5 6 2 Nulling Potentiometers amp Arm Re
19. ce simultaneously When the beam is forced down 250ye change the resistance in C decreases by 0 175 ohm and resistance A increases by 0 175 ohm as shown in the 4 bridge example above The bridge voltage Vu is then Vor 10V 350 700 350 0 175 350 0 175 350 0 175 Vor 10V 350 700 349 825 700 Voir 2 500mV 19 Choosing Gain X1000 would result in 2 5 Y being applied to the DAS board Choosing Gain X 2500 X1000 on the input channel and X2 5 on the output could result in an amplified voltage that s out of the DAS board s range In this case the excitation voltage could be reduced to 4V reducing the bridge voltage to 1 00mV A gain selection of 2500 would then present a maximum voltage of 2 5V to the DAS board Full Bridge Example Full bridge strain gauges consist of all four bridge resistors Figure 5 8 Obviously no bridge completion resistors are installed on the board when using this configuration EXCITATION VOLAGE EXCITATION VOLTS SENSE LOW Null Pot EXCITATION VOLTS SENSE HIGH TO CHANNEL 80Hz Low MULTIPLEXOR Pass Filter Figure 5 8 Full Bridge Simplified Schematic Full bridge calculations With four active strain gauge elements these are four times more sensitive than a 1 4 bridge All four resistors are strain gauges and are attached to the beam in the following configuration Gauge resistors C and B are on
20. change twice as much as the strain does A change of 1 micro strain means that the resistance of the strain gauge has changed by 2 ppm or 0002 0001 x 2 For a 350 ohm strain gauge with GF 2 a lue change results in a resistance change of Resistance change SG Resistance x change in length x Gauge Factor 350 ohm x 000001 x 2 0 0007 ohm 7 1 2 Specification of Strain Gauges Metal Foil gauges are available in 120 350 and 1000 ohms Semiconductor strain gauges exist and have resistance of up to 10000 ohms They can readily be used with the CIO EXP BRIDGE16 but may not be as linear as metal foil gauges Maximum strain allowed is 3 to 5 depending on type and thickness of strain gauge material This means a limit of 30 000 to 50 000UE or a maximum resistance change of 6 to 10 Strain Gauges are typically used to calculate a change in strain that is the difference between the unstrained and the strained state 7 2 Reference Material for Application of Strain Gauges The Bonded Electrical Resistance Strain Gage First Edition by William M Murray and William R Miller 1992 424 pages ISBN 0 19 507209 X Available from Society for Experimental Mechanics order OX 2 Strain Gage Users Handbook First Edition 1992 424 pages ISBN 0 912053 36 4 Published by Society for Experimental Mechanics order ELS 017 23 The Art of Practical and Precise Stain Based Measurement by James Pierson 1992 400 page
21. d for DAS boards The inputs are suitable for connecting a voltage to the DAS board so it can be measured The CIO EXP BRIDGE16 is a one of sixteen multiplexer which means that for every channel in your DAS board you can multiplex sixteen different signals to it You can expand the number of inputs of your DAS board by sixteen for every CIO EXP BRIDGE16 board up to the number of inputs on the DAS board For example a DASOS has eight inputs Eight times sixteen is one hundred and twenty eight Thus by using sixteen CIO EXP BRIDGE16 boards you could bring 128 inputs into a PC with only one DASOS in one PC slot Using a DAS16 up to 256 inputs could be accommodated It is unlikely that you purchased a CIO EXP BRIDGE16 to measure only voltages The board was designed for bridge sensors For voltage only measurements a CIO EXP16 or CIO EXP32 would be less expensive and would do the same job However if you have only one or two voltages to measure in addition to bridge sensors you can use the CIO EXP BRIDGE16 4 1 Channel Selection The General Configuration section describes the channel selection setting the jumper and verifying the installation and operation of the CIO EXP BRIDGE16 with your data acquisition board Configure your boards as described in that section before continuing with this section 4 2 Powering the CIO EXP BRIDGE16 The General Configuration section describes the power selection options setting the power select switch and
22. e ground of the power supply and the ground of the personal computer should be tied together through a heavy gauge wire If you do not strap the two grounds together a voltage difference between theses grounds will affect measurements If the potential exceeds the protection range of the input circuits the board may be damaged At this time ignore the other screw terminals located next to the power and ground terminals They are needed only with certain sensors and will be explained in those sections 3 6 Daisy Chaining CIO EXP BRIDGE16 Boards Connect one CIO EXP BRIDGE16 to another using a C37FF ribbon cable Connect from P2 on the upstream board to P1 on the downstream board Make sure each of the boards in the chain have a unique channel selected CH SEL jumper is set to a different number on each board 3 7 Connecting a Test Voltage Make your initial test of the CIO EXP BRIDGE16 with a voltage signal of between 5 and 5V If you use an AC signal source keep the frequency below 70Hz to avoid attenuation by the CIO EXP BRIDGE16 s low pass filter Each bridge input circuit has four screw terminals These terminals are shown in Figure 3 6 below To connect a voltage signal to the input circuit connect the voltage to the screw terminals as follows Jo d SENSE Connect to voltage UE T r SENSE Jumper this to P Z 7 tr tr P Connect to ground P No connection CHO Figure 3 6 Inpu
23. fferential Each channel individually switch selectable for X1 X10 X100 or custom and board gain switch selectable for X1 or X2 5 0 01 typical 0 15 maximum 0 02 typical 0 35 maximum 0 05 typical 0 40 maximum 0 20 typical 0 90 maximum 0 045 typical 0 045 typical 0 075 typical 0 1596 typical Each channel adjustable to zero 10ppm C typical 15ppm C typical 20ppm C typical 20uV Ctypical 6uV C typical 5 1uV C typical S IuV C typical 10V Gain 10 25 100 250 1000 2500 100dB typical Gain 1 2 5 Channel to channel settling time SV step to 01 Absolute maximum input voltage Miscellaneous 94dB typical 250us 15V Each input channel has a 79Hz low pass filter X2 5 gain is adjustable for zero error Jumper selects compatibility with DASO8 or DAS 16 series Locations provided for bridge completion resistors for each channel Locations provided for bridge nulling pots and resistors for each channel 21 Analog Output Output Amplifier type Number of channels Maximum Output Range Current Drive Output short circuit duration Output coupling Output impedance Miscellaneous Digital Input Output Digital type DIn 0 through 2 DIn 3 Configuration Input low voltage DIn 0 through 2 DIn 3 Input high voltage DIn 0 through 2 DIn 3 Voltage Excitation Section Excitation voltages Sources for excitation voltage Current 5V source 4V VEXC 12V source 10V VEXC
24. lable options how to configure the various switches and jumpers to match your application requirements and will create a configuration file that your application software and the Universal Library will refer to so the software you use will automatically have access to the exact configuration of the board Please refer to the Software Installation Manual regarding the installation and operation of InstaCal Use InstaCal along with the following hard copy information to set the hardware configuration of the board 3 GENERAL CONFIGURATION 3 1 A D Board Type Select Jumper The CIO EXP BRIDGE16 may be used with either DASO8 or DAS16 family boards because the signal assignments of the 37 pin connectors match those of the DASOS and may be adapted to those of the DAS16 with a C EXP2DAS16 10 cable Select the A D board type via the JB10 jumper Jumper JB10 on the CIO EXP BRIDGE16 located near the 37 pin connector selects the A D board family as DASOS8 or DAS16 j E Figure 3 1 shows the jumper set to use the CIO EXP BRIDGE16 with a CIO DASOS family board DASO8 DAS16 Figure 3 1 DAS08 16 Select 3 2 Setting The Output Channel Jumpers labeled CH SEL located near the 37 pin connector select the A D board channel that the output from the active sensor will be connected to There are 16 jumper positions for outputs each corresponding to one of the 16 output pins on the 37 pin connectors When the board is connected to a DASOS o
25. mum strain to be measured will be 250ue 250 micro strain Knowing the amount of force required and the size of the beam is not necessary since strain relates to the change in length of the surface of interest The Strain Gauge will be a metal foil type 350 ohms resistance Gauge Factor 2 Refer to the Appendix for information on these specifications A Quarter Bridge Example For 4 bridge circuits the strain gauge has a single resistive element that is connected as one leg of the bridge The other three legs must be populated with the precision completion resistors EXCITATION VOLTS SENSE LOW EXCITATION VOLTS EXCITATION VOLAGE Null Pot SENSE HIGH TO CHANNEL MULTIPLEXOR 80Hz Low Pass Filter Figure 5 6 4 Bridge Circuit Simplified Quarter Bridge Calculations The strain gauge is applied to the top of the beam This strain gauge takes the place of resistor A see Figure 5 6 Three other 350 ohm resistors B C and D complete the bridge circuit These are installed by the user in locations provided on the board or attached to the screw terminals As downward force is applied the strain gauge on the top of the beam is stretched Therefore its resistance increases by Strain Gauge increase 350 ohm x 250 x 10 x 2 0 175 ohm Thus the value of gauge A under tension will be 350 175 ohms when the strain on the beam is 250ue Initially choosing an excitation voltage of 10V the
26. nded mode is selected by installing a jumper between the signal input low CSENSE and ground P The SENSE terminal is then connected to the signal ground and the SENSE terminal is connected to the signal 4 6 2 Floating Differential A floating differential input has two wires from the signal source and a 10K ground reference resistor installed at the CIO EXP BRIDGE16 input The two signals from the signal source are Signal High and Signal Low The reference resistor is connected between the CIO EXP BRIDGE16 SENSE and P pins and the Signal Low is connected to the SENSE terminal The SENSE terminal is connected to the Signal High A floating differential hookup is handy when the signal source is floating with respect to ground such as a battery The floating differential input will reject up to 10V of EMI energy on the signal wires CAUTION Determine that the signal source is actually floating Check it with a voltmeter before risking the CIO EXP BRIDGE16 and PC 4 6 3 Fully Differential A differential signal uses three wires from the signal source The signals are Signal High Signal Low and Signal Ground LLGND Signal High is connected to the SENSE terminal and Signal Low is connected to the SENSE terminal The ground reference must be connected to the P terminal A differential connection allows you to connect to a signal source with a ground that is different than the PC ground but less than 10V difference and still
27. nly the first eight channels labeled 0 7 can be used When the board is connected to a DAS16 any one of the 16 jumper positions can be selected In each case the jumper position corresponds to a channel number on the A D board See Figure 3 2 37 Pin OUTPUT CHANNEL CONNECTOR SELECT JUMPER INPUT 0 INPUT 1 L3 INPUT2 INPUT3 INPUT4 INPUT 5 INPUT 6 INPUT 7 1 2 I 71 1 I I Dr 34 0 9 ve b 4 0 I DN BR 0 D ol e eee wv w wo e i ww 43X31dILINN TANNVHO 8 32 a a 0 3 Qt I I I 1 a 30 Od 1 I I I 1 1 e e N INPUT 9 INPUT 13 C e p e vw d 285 eeeee 6 1 5 Le d p S 43X31dILINN TANNVHO I I I T T D 14 e el b IMUX ADDR 4 MUX ADDR 3 IMUX ADDR 2 A IMUX ADDR 1 Figure 3 2 Output Channel Jumper JB6 CH SEL JB16 Figure 3 3 is a diagram of the Channel Select jumper blocks shown using channel 0 of the A D board LA A AAA 01234567 8 9 101112131415 CHANNEL 0 SELECTED FOR SENSOR OUTPUT Figure 3 3 Output Channel Select Jumpers Place the jumper on the pin which corresponds to the A D board s input channel A second set of jumpers is marked VEXC SEL excitation voltage select This jumper connects the excitation voltage used for the bridge excitation
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29. on section describes the channel selection setting the jumper and verifying the installation and operation of the CIO EXP BRIDGE16 with your data acquisition board Configure your boards as described in that section before continuing with this section 5 2 VEXC Jumper Select There is a set of jumpers near the 37 pin connector labeled VEXC SEL which stands for channel excitation voltage select This jumper will connect the on board excitation voltage to one of the A D board channels so that it may be measured OMEGA Engineeering does not use a measurement of the excitation voltage in any of its software You do not need to set this jumper if you are using the CIO EXP BRIDGE16 with OMEGA Engineeering software or with packages such as Labtech Notebook which use the Universal Library Use this jumper only with software from other manufacturers that specifically require it 5 3 Powering The CIO EXP BRIDGE16 There are two power issues to address The first is the source of the 5 volt power to the board The second is the source of the bridge excitation voltage power 5 3 1 Selecting the Power Source for the Board The General Configuration section describes the power selection options for powering the CIO EXP BRIDGE16 itself Configure your boards as described in Powering the CIO EXP BRIDGEI6 in the General Configuration section before continuing with this section 5 3 2 Selecting the Power Source for the Excitation Voltage Bridge sensors c
30. onsume a lot of power In some cases the bridge sensors consume so much power that if fully populated with 16 sensors the on board excitation circuit would not have adequate power to supply all 16 sensors This is an extreme case but is indicative of the attention you must pay to power requirements when using bridge sensors Also when selecting the power source for the excitation voltage consider the voltage you will use for excitation The options available are 0 5 1 2 4 and 10V In general higher excitation voltages are better because a higher voltage increases the difference between the balance points of the bridge circuit which increases the accuracy of your measurement The excitation voltage must be less than the source 12 Jumper JB11 Figure 5 1 located near the bottom edge of the board selects the source of the bridge excitation voltage The three choices are 5V the same 5V source chosen for board power above 12V from the PC through the 37 pin connector or PEXT an external power supply connected at the P EXT screw terminal JB11 As x im R s ATI LX d Figure 5 1 Output Gain amp Power Select If you choose a separate power supply it must be a floating isolated supply one with three terminals Do not tie the GND and V terminal together It must not exceed 15V The 5V and 12V jumpers are only valid with CIO DASOS family boards The 12V jumper is not valid with the CIO DAS08 AO and PGx
31. polar 5V range would be the best choice If the range on your A D board is fully programmable the software you use for measurement will determine the range 3 4 CONNECTING THE CIO EXP BRIDGE16 TO THE A D BOARD 3 4 1 Connecting to a DAS08 Series A D Board A CIO DASOS series board may be connected directly through a C37FF series cable from the Pl connector on the CIO EXP BRIDGE16 to the A D analog connector The JB10 jumper should be left in the DASOS position as set at the factory 3 4 2 Connecting to a DAS16 Series A D Board Connection to a DAS16 series board requires a special 37 conductor cable C EXP2DAS16 10 since pin relationship of CIO EXP and DAS16 signals is not 1 1 Install the C EXP2DAS16 10 cable connector labeled MUX into the P1 connector of the CIO EXP BRIDGE16 board and the other end into the DAS16 series board s analog connector 3 4 3 Other A D Boards For other boards use this connector diagram Figure 3 4 to construct a cable or call us and f b discuss the possibility of a custom manufactured NC LLGND 5 9 e cable LLGND OUTPUT 8 18 e 37 OUTPUTO 36 OUTPUT 1 The signals from the CIO EXP BRIDGE16 are ouo r 5 OUTPUT voltages from each channel and an analog ground SOIPUPM 5 0 e 34 OUTPUT3 There should be no voltage between analog eure u e 33 OUTPUT4 ground and power ground GUTES 9 e 32 OUTPUTS The MUX address lines control the setting of the OUIPUPIS 12 BS input channel multiplexer s
32. s 800 10 Ohms The equation for selecting the USER gain resistor between X100 and X1000 gain is Ruser 15 40000 Gain 1 40 5 6 Configuring the Bridge As mentioned earlier in this chapter resistance measurements are made by constructing a bridge containing precision resistors with known values against which the unknown resistor is to be compared In strain gauge applications the strain gauge sensor itself may make up a quarter of this bridge half of this bridge or the entire bridge Examples of each of these configurations follow Figure 5 5 is a schematic of the bridge circuit EXCITATION VOLAGE EXCITATION VOLTS SENSE LOW Null Pot EXCITATION VOLTS SENSE HIGH TO CHANNEL 80Hz Low MULTIPLEXOR Pass Filter Figure 5 5 Bridge Circuit Resistance Change vs Sense Voltage Change This table shows how the measurement at the Leg Obms Ohms A D board varies with respect to an increase Volts Volts or decrease of the resistance in one of the legs of the bridge Volts Volts Volts Volts Volts Volts Read the table by selecting the leg you are interested in and looking across that row to the Volts indication under the column heading for the expected change in resistance For example if you are interested in leg A and want to know what the relative change in volts at the A D board will be if the resistance is increased look under Ohms
33. s in 3 ring binder ISBN 1 895976 00 6 Available from Society for Experimental Mechanics order JP 001 Strain Gage and Transducer Techniques 1984 72 pages Published by Published by Society for Experimental Mechanics order S 023 Society for Experimental Mechanics 7 School St Bethel CT 06801 203 790 6373 24 EC Declaration of Conformity CIO EXP BRIDGE16 Bridge inputs for ISA bus Part Number Description to which this declaration relates meets the essential requirements is in conformity with and CE marking has been applied according to the relevant EC Directives listed below using the relevant section of the following EC standards and other normative documents EU EMC Directive 89 336 EEC Essential requirements relating to electromagnetic compatibility EU 55022 Class B Limits and methods of measurements of radio interference characteristics of information technology equipment EN 50082 1 EC generic immunity requirements IEC 801 2 Electrostatic discharge requirements for industrial process measurement and control equipment IEC 801 3 Radiated electromagnetic field requirements for industrial process measurements and control equipment IEC 801 4 Electrically fast transients for industrial process measurement and control equipment Carl Haapaoja Director of Quality Assurance OMEGA Engineering Inc One OMEGA Drive Stamford Connecticut 06801 800 872 9436 Fax 203 359 1660 E mail inf
34. sistor Each circuit has a position for a nulling potentiometer and associated Arm resistor The purpose of the nulling arm is to allow you to zero the reading of strain at a given strain position There is no formula to use to select the nulling potentiometer and arm resistor Bridge resistor values and total gain selected for the CIO EXP BRIDGE16 will affect adjustability for a given nulling circuit An average value for the arm resistor is 10k ohms Start with that and adjust as required 5 6 3 Strain Gauge Bridge Configuration Examples Following are three typical strain gauge bridge configurations They are by no means the only way to connect a strain gauge For example there is no rule that says the A leg must be the strain gauge on a La bridge implementation The examples below show how to translate strain to input voltage for the strain gauge configuration used to measure simple bending strain Other types of stress and strain axial torsion shearing etc are beyond the scope of this description These examples can be used to as a guide for calculating the bridge voltage in your own application and thus help you select the proper amplifier gain and excitation voltage The use of quarter bridge half bridge and full bridge strain gauges are described 17 The Application In these examples imagine a beam extending out from a fixed point on a wall Force is applied to deflect the end of the beam downward We know that the maxi
35. t Screw Terminal Strip The four screw terminals associated with each input circuit are labeled on the CIO EXP BRIDGE16 as follows SENSE High side of input P Excitation voltage return SENSE Low side of input P Excitation voltage The use of the terminals is dependent on the type of sensor you have connected to the input circuit The nomenclature on the terminals has been chosen to be appropriate for bridge sensors 3 8 Verifying The Installation For verification of the installation leave any switches or jumpers not mentioned above in their default positions Each of the gain switches CHO through CH15 and S17 7 should be off toward the upper edge of the board for a gain of X1 unity gain To verify the installation use the InstaCal program installed on your computer This software came with your A D board if you bought the board from the same manufacturer as the CIO EXP BRIDGE16 If your A D board is not from the same manufacturer but is compatible please call technical support and request a copy of InstaCal Use InstaCal s TEST option to verify that a signal present at one of the CIO EXP BRIDGE16 inputs can be read You will not need to set any jumpers other than those previously mentioned and should not set any switches or install any passive components until you have verified the installation 6 4 CONFIGURATION FOR VOLTAGE MEASUREMENT The CIO EXP BRIDGE16 is an amplification signal conditioning and multiplexing front en
36. t range of the A D board you should do a similar calculation and set switches on the CIO EXP BRIDGE16 for the required gain Remember to make sure that the settings in InstaCal match the switches on the DAS and CIO EXP BRIDGE16 boards When using strain gauges the expected output from the sensor should be calculated and the gain of the CIO EXP BRIDGE16 set accordingly There are some examples at the end of this chapter detailing these calculations You may also find it helpful to refer to the Appendix for additional strain gauge information 5 5 Setting the Gain Once you have determined the gain required for your application set the gain of the CIO EXP BRIDGE16 using the following guide Amplification for ALL channels board output gain is switch selectable S17 for X1 or X2 5 Input amplification for EACH CHANNEL is switch selectable CHO through CH15 for X1 X10 X100 or X1000 A user specified gain may be set by supplying a precision resistor at position RX and setting the U option on switch CH to ON 5 5 1 Setting Board Gain There is a switch on DIP switch block S17 Figure 5 3 labeled X1 and X2 5 Sliding this switch down amplifies the output of the multiplexers by 2 5 The factory default position up has a gain of 1 unity The X2 5 gain switch is useful in some voltage and bridge measurements If you desire a NDA voltage gain of 2 5 25 250 or 2500 set this 2 switch down i Figure 5 3 Board Gain The
37. to one of the A D channels for monitoring Installation of this jumper is optional If you decide to monitor excitation voltage make sure you install this jumper on a different channel number than that selected for the CH SEL jumper One individual channel must be selected for each bank of 16 EXP channels For example if you are using several CIO EXP BRIDGE16 boards the jumper setting for each board must be unique If you select channel 0 for the first board do not use this channel for any of the other boards 3 3 Configuring the A D Board 3 3 4 DASO8 Family Setup The input mode of the A D board must be single ended to be compatible with the CIO EXP outputs Some of the boards in the DASOS series have differential inputs that can be converted to single ended inputs See the information shipped with your A D board for conversion to single ended inputs 3 3 2 DAS16 Family Setup The input mode of the A D board must be single ended to be compatible with the CIO EXP outputs Most of the DAS16 series is switch selectable for either 8 differential or 16 single ended inputs When used with the CIO EXP set the switch to 16 channel single ended mode 3 3 3 All A D Boards If you are using an A D board with switch selectable ranges consider the application and determine the best fit for range vs expected voltage For example when measuring resistance such that the output of the EXP board is expected to be in the range of 3 to 4 5 Volts a uni
38. uitable resistor for Rb Then use this formula to calculate Ra Ra A 1 x Rb You will need to construct the voltage divider remote from the CIO EXP BRIDGE16 board 4 6 Connecting Voltage Signals Voltage input signals can be single ended or differential In addition the full scale may have to be matched to the range of the CIO EXP BRIDGE16 and DAS board combination using amplification or attenuation To connect a voltage and make an accurate measurement both of these factors must be considered see section 4 3 After the range has been matched and the signal connected the measurement is made using the DAS board and software You can use InstaCal to display the value read on any channel of the CIO EXP BRIDGE16 Each input circuit has four screw terminals associated with it These terminals are shown in Figure 4 4 To connect a voltage signal to the input circuit you need only use three screw terminals These are Q Q Q S SENSE High side of a differential or single ended voltage signal Fa re aal e SENSE Signal low or CH LO on a DAS board Must be jumpered to P z for single ended a amp P Ground of a differential voltage signal or Low side of a single ended signal CHO Figure 4 4 Input Screw Terminal Strip 10 4 6 1 Single Ended A single ended input has two wires connected to the CIO EXP BRIDGE16 a signal high and a Low Level Ground LLGND The LLGND signal must be the same ground the PC is on Single e
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