Model 8510 PIEZOBALANCE Respirable Aerosol Mass
Contents
1. If the sensor needle does not read in the correct zone of the meter make sure that the sensor cleaning dial is firmly locked in the 12 o clock position If it still does not read properly see Chapter 5 Troubleshooting Figure 17 Checking the precipitator current level 19 20 Step 8 Press the STRT button The sensor frequency is displayed approximately 2 seconds after you press the STRT button To ensure accurate readings this value should be within 1000 Hz of the Basic Frequency The frequency change is displayed every 10 seconds for the 120 second time and every 2 seconds for the 24 second time The PIEZOBALANCE uses the frequency change to calculate the mass concentration of respirable particles The aerosol concentration is displayed after 120 seconds for the 120 second measuring time and after 24 seconds for the 24 second measuring time This reading remains on the screen until you shut off power or make a new measurement If you use the 24 second time you must multiply the displayed concentration by 5 as indicated by the X 5 light on the display panel Figure 18 Figure 18 Concentration of respirable aerosol displayed for 24 second sample Step 9 After the concentration from the test is displayed and recorded press the CHK button or switch off the power This step is important because it stops the instrument from collecting particles on the sensor The PIEZOBALANCE continues to collect particles on the s2. and 3 Then carefully follow the instructions to prepare the instrument for operation Unpacking The following items are included with the PIEZOBALANCE if anything is missing or damaged notify TSI promptly Qty Item Part No 1 Pin vise 1502245 1 Offset Phillips head screwdriver 3012028 1 Vacuum grease 1502249 1 Sponge squeezer 1502260 1 Operation and Service Manual 1980037 2 Small drop bottles 2002007 2 Plastic bottles 2002008 1 Screw cap 2002009 1 O ring EPDM 1 115 2501525 1 O ring EPDM 1 021 2501526 1 O ring EPDM 1 019 2501527 2 O ring EPDM 1 014 2501528 2 O ring EPDM 1 011 2501529 4 Sensor cleaning sponges 1502248 2 Cassette sponge holders 1502235 1 Battery Charger 115V or 8501 Battery Charger 230V 8504 1 Cleaning Solution 2915013 A registration card is located at the front of this manual Please complete it promptly and drop it in the mail This allows TSI to inform you of any product updates Figure 1 PIEZOBALANCE and accessories Parts The following items are included with the PIEZOBALANCE if anything is missing Identification damaged notify TSI promptly RN GUS EOS AL ANCHE RAESSIRABLES A EROS A Data Display HZ Light MG M3 Light X 5 Light NEG Light PWR Pushbutton STRT Pushbutton MEAS Pushbutton AR HABE OT Figure 2 Front of PIEZOBALANCE 9 10 11 12 13 14 15 16 Sensor CHK Pushbutton MEAS TIME Button BATTERY VOLTAGE Indicator PRECIPITATOR CUR
3. record the frequency displayed this is your fq reading Step 7 Continue sampling for a period of 5 to 20 minutes Disregard the concentration that is displayed after 2 minutes The sensor will continue collecting respirable aerosol until you push the STRT button again 21 22 High Concentration Measurements Step 8 When the desired sampling time has been reached push the STRT button After 2 seconds record the frequency that is displayed this is your fy reading Step 9 To calculate the measured concentration use the following equation C 0 333 mg w 1 Where C Aerosol concentration in mg m Sample measurement time in seconds Frequency read at beginning of measurement Hz Frequency read at end of measurement Hz m mh ot N e oil You can make high concentration measurements 10 to 20 mg m by recording frequency changes manually and then performing a simple calculation Ignore displayed mass concentration readings when using this procedure For high concentration measurements the sample aerosol must be sticky such as cigarette smoke to adhere sufficiently to the sensor To make a measurement follow these eight steps Step 1 Clean the sensor Step 2 Press PWR Step 3 Select the 24 second time Step 4 Press the MEAS button You must press the STRT button Step 5 within 12 seconds of pressing the MEAS button Step 5 Press the STRT button The aim is to record five or six frequ
4. Caution As you are making the adjustments do not touch the capacitor shown in Figure 42 with a metal screwdriver This will destroy the circuit To avoid this wrap the metal shaft of your screwdriver with electrical tape Figure 42 Adjusting the flow rate Step4 Continue a sequence of adjustments and flow checks until the flow rate is 1 00 0 05 liters per minute Chapter 4 Chapter 5 Troubleshooting Symptom Sensor frequency is too high compared to Basic Frequency Hz 1000 Basic Frequency Precipitator current is low or unstable Digital readout does not display a number or PIEZOBALANCE fails to complete cycle Precipitator current is low or unstable Vacuum pump sounds loud and erratic Possible Causes Sensor is not thoroughly cleaned Sensor cleaner knob is not returned to lock position The precipitator needle is dirty Logic circuitry has stopped Sensor cleaner knob is not returned to lock position The precipitator needle is dirty Vacuum pump is dirty Solution Rinse sponges thoroughly and rewet Make sure sponges protrude sufficiently from the cassette but do not protrude too far Clean sensor as described by Sensor Cleaning under Maintenance Return sensor cleaner knob to 12 o clock position with a firm quick twist Clean precipitator needle assembly Switch power off then restart Return sensor cleaner knob to 12 o clock position with a firm quick twis
5. The combination of flowing air and the electric field generated by the precipitator needle carries the particles to the electrode surface of the piezoelectric crystal The high adhesive force between the particles and the surface causes the particles to stick firmly to the surface When a quartz crystal or other piezoelectric material is placed in an electric field the crystal becomes mechanically stressed Conversely if a piezoelectric material becomes mechanically stressed electric charges of like polarity appear on certain surfaces of the material When a piezoelectric material is made part of an electrical driving circuit the piezoelectric material vibrates with a precise natural frequency depending on the orientation of the cut of the crystal with respect to the axis of the raw crystal and on the thickness and density of the crystal For a given cut the natural frequency of the crystal depends on the mass of material that sticks to its surface The addition of mass to the surface of a given crystal causes the natural frequency to decrease in direct proportion to this added mass This is similar to the decrease in frequency of a vibrating mechanical spring mass system when more mass is added to the system The piezoelectric crystal sensor used in the PIEZOBALANCE is an AT cut quartz crystal These crystals vibrate in the thickness shear mode In the fundamental thickness shear mode the vibrational node is a plane passing through the center
6. along with the instrument s data readout and function keys are represented in this manual by the typeface called Helvetica Narrow Reference to section titles of the manual are identified by italics Example 1 Press the PWR button from Making a Measurement in Chapter 2 Example 2 See Cleaning the Sensor under Maintenance from Chapter 2 To call your attention to an important note or comment a black four pointed star is used About This Manual Introduction The Model 8510 PIEZOBALANCE Respirable Aerosol Mass Monitor is a reliable easy to use portable instrument for measuring the mass concentration of smoke fumes dust and other airborne particles It offers numerous applications including tuning ventilation systems and performing a quick check of problem areas for OSHA compliance The PIEZOBALANCE uses the piezoelectric technique similar to a microbalance for determining aerosol mass concentrations This technique is based on the inherent stability of a quartz crystal If the crystal experiences mass accumulation its natural frequency changes This frequency is measured by the instrument and related to the mass concentration of the sampled air The value for mass concentration is then displayed in milligrams per cubic meter Introduction Chapter 1 Set Up The PIEZOBALANCE is easy to set up First verify that no components are missing refer to the following parts list and to the labelled photographs Figures 1 2
7. and remove it Figure 10 Removing the sponge compartment door Step 8 Slide the tray into the PIEZOBALANCE with the exposed surface of the sponges face downward Figure 11 Slide in the tray until you hear a click The click means the tray is locked in place Replace the sponge compartment door It may be necessary to hold the sensor cleaning dial in the 12 o clock position as you replace the door Set Up 11 12 Figure 11 Installing the sponge tray The preliminary steps needed before operation of the PIEZOBALANCE should now be completed Chapter 2 Description of Parts and Functions will help you learn more about your instrument Chapter 1 Control Panel Data Display Chapter 2 Description of Parts and Functions The control panel of the PIEZOBALANCE is shown in Figure 12 Its functions are described below The data display has four indicator lights these define what is being displayed HZ Light 1 Figure 12 indicates that a sensor frequency measurement is being displayed MG M3 Light 2 Figure 12 indicates that a mass concentration in milligrams per cubic meter is being displayed X 5 Light 3 Figure 12 indicates that the displayed concentration must be multiplied by a factor of 5 to obtain the correct reading The X 5 light becomes active when you select the 24 second sampling time NEG Light 4 Figure 12 indicates that the displayed concentration is in error specifically the change in freque
8. manually You need a cotton swab and one of the following alcohol detergent or dilute ammonia Step1 Turn the Sensor cleaning dial 10 degrees Figure 25 Figure 25 Sensor cleaning dial turned 10 degrees Step 2 Remove the aerosol inlet panel by pulling up on the center of the nylon locks Step 3 Moisten a cotton swab with detergent alcohol or dilute ammonia Step 4 Depress the vertical spring that lowers the sensor and holder Figure 26 If you cannot easily depress the spring make sure the cleaning knob is turned 10 degrees Chapter 4 Figure 26 Positioning the sensor assembly for cleaning Step5 Clean the sensor with the swab Figure 27 Figure 27 Cleaning the sensor with the fast method Step6 Complete a normal cleaning cycle using the cleaning knob Repeat steps 3 through 6 as needed until the sensor frequency falls within 1000 Hz of the Basic Frequency Maintenance 31 32 Battery To charge the batteries plug the charger unit into the charge port Figure 28 Charging Although the batteries require 15 hours to charge completely the instrument MAY BE USED DURING CHARGING Figure 28 Charging the Battery Pack Removing and An impactor is installed in the sampling inlet to remove particles above 3 5 Greasing the micrometers Each day be sure to clean the impactor and apply a light coat of Impactor Vacuum grease or as needed depending on the operating conditions To remove the impact
9. of your measurements are above 3 0 milligrams per cubic meter it will be easier to use the 24 second time for sampling between 2 0 and 3 0 milligrams per cubic meter If the concentration from the initial test exceeds 10 0 milligrams per cubic meter or falls short of 0 01 milligrams per cubic meter see either Low Concentration Measurements or High Concentration Measurements under Special Applications at the end of this chapter Making a To make a mass concentration measurement with the PIEZOBALANGE follow Measurement these eleven steps Step 1 Select the appropriate measurement time see previous section Step 2 Press the PWR button Step 3 Check the battery voltage indicator It should read in the center of the blue region Figure 14 If not see Charging the battery in Chapter 4 E pa ee tage Figure 15 Checking the battery vol Step 4 Press the CHK button and then the STRT button Step 5 Compare the frequency displayed with the Basic Frequency The BASIC FREQ is posted on the label on the inside of the sponge compartment door Figure 16 If the displayed frequency exceeds the Basic Frequency by 1000 Hz or more you must clean the sensor 18 Chapter 3 Operation Figure 16 Comparing the sensor frequency with the Basic Frequency Step 6 Press the MEAS button Step 7 After a few seconds make sure the precipitator current needle has risen and stabilized in the central black region of the meter Figure 17
10. pass through the impactor while some particles smaller than the cut off diameter impact out At a given cut off diameter 50 percent of the particles of the cut off diameter size impact out while 50 percent pass through Theory of Operation 47 Precipitator The precipitator block of the PIEZOBALANCE is constructed of Teflon an Piezoelectric Microbalance excellent electrical insulator that is inert to most chemicals found in ambient air or mobile exhaust The size and shape of the precipitator chamber is designed to optimize the collection efficiency of the sensor Because the sensitivity of the piezoelectric microbalance depends inversely on the area of the crystal electrode the diameter of chamber is as small as possible The depth of the chamber distance from the precipitator s needle point to the sensor plane is large enough to allow time for particles to become charged and precipitate yet small enough to maintain a stable corona current with reasonable voltages Experimental results for collection efficiency agree well with detailed calibrations based on electrostatic charging and precipitating theory Since the precipitating chamber is made of Teflon its inner surface carries a high surface charge with the same polarity as the particles making deposition on the chamber walls negligible The high voltage power supplied to the precipitator needle operates at constant corona current assuring constant particle collection efficiency
11. rotating the knob counterclockwise until it locks at the 12 o clock position Step 6 Compare the sensor frequency with the Basic Frequency If the displayed frequency is decreasing it is because the sensor is still drying When the frequency stops decreasing compare the frequency with the Basic Frequency If it is still 1000 Hz or more above the Basic Frequency repeat steps 1 through 5 above Stubborn Sometimes the sensor s frequency cannot be reduced to within 1000 Hz of the Deposits Basic Frequency by using the standard cleaning method outlined above When this occurs two options are available the patient method and the fast method of cleaning stubborn deposits from the sensor are both described below Patient Method Most deposits can be removed from the sensor with a single cleaning However some sticky deposits such as tobacco smoke may require a longer soaking time Simply increase the time in the wait position 10 to 50 minutes usually works in step 3 of Cleaning the Sensor For extreme cases an overnight soaking may be necessary Leave the knob at the step 3 position Turn off the power and let the sensor soak overnight Caution Do not however leave the PIEZOBALANCE in this position for an extended period several days The sponges will dry out and damage the sensor Maintenance 29 30 Fast Method To remove stubborn deposits from the sensor quickly follow the six steps listed below for cleaning the sensor
12. tip to crystal electrode charges the particles The electric field causes them to collect on the sensing crystal A pump draws the air through the impactor and precipitator and then out the sensing area 45 Measurement Technique Before Sampling After Sampling 46 The PIEZOBALANCE uses the piezoelectric microbalance technique for determining airborne particle mass concentrations It contains two piezoelectric crystals that are made to oscillate at a highly stable resonant frequency One crystal is used as a reference crystal and the other as the sensing crystal Since the resonant frequency is a function of the mass the resonant frequency decreases in direct proportion as mass is collected on the oscillating region of the sensing crystal A mass concentration measurement is calculated using the change in the two frequencies over a given period of time A simple analogy helps explain the technique With a clean sensing crystal the output of the PIEZOBALANCE is related to the difference between the reference crystal frequency and the sensing crystal frequency This value is fixed for each instrument it is referred to as f nn _ _ ee Figure A 2 Piezoelectric microbalance technique before sampling As particles are charged and precipitate onto the sensing crystal the difference between the frequency of the sensing crystal and the frequency of the reference crystal increases in direct proportion to the ma
13. to read the direct mass concentration of a substance that is in an aerosol to determine the 8 hour average exposure directly or to measure nonstandard aerosols such as cotton dust The mass sensitivity can be changed to read the mass concentration of a specific substance if the percent by weight of the substance is known from chemical analysis or other means In this case the mass sensitivity of the instrument would be reduced to the same percent of the factory calibrated level as the percent of the substance to be measured For example if an environment is determined to contain 20 by weight of lead the mass sensitivity of the instrument could be reduced to 20 of the original sensitivity For a factory calibrated sensitivity of 0 00278 mg m the sensitivity would be changed to 0 00278 x 20 000556 mg The readout of the instrument would now give the concentration of lead only Note that the decimal point will need to be artificially placed with tape on the display one place to the left The PIEZOBALANCE can give readings for 8 hour average exposure levels by changing the mass sensitivity In order to do this the average 8 hour exposure must be predetermined by previous sampling Use the PIEZOBALANCE to take random samples during an 8 hour period and then divide the two values as follows Average 8 hour exposure predetermined Average of PIEZOBALANCE readings The mass sensitivity is then adjusted as follows New mass sensi
14. 0 seconds Dimensions LWH 170 mm Weight 12 3 in x 5 2 in x 6 7 in 310 x 130 x 9 5 Ib 4 5 kg Power batteries Battery life Built in rechargeable Ni Cd 8 hour operation at 50 duty cycle 15 hours Recharge cycle The upper size limit is determined by the 50 cut off size of the impactor 55 56 Appendix C Appendix D Assembly Drawing Appendix D
15. Model 8510 PIEZOBALANCE Respirable Aerosol Mass Monitor Operation and Service Manual Model 8510 PIEZOBALANCE Respirable Aerosol Mass Monitor Operation and Service Manual February 1993 P N 1980037 RevA TSI Incorporated P O Box 64394 500 Cardigan Road St Paul MN 55164 USA Sales 800 876 9874 Customer Service 612 483 4711 w Part number 1980037 Rev A Copyright TSI Incorporated February 1993 All rights reserved Address TSI Incorporated 500 Cardigan Road P O Box 64394 St Paul MN 55164 USA Telex No 6879024 LIMITATION OF WARRANTY AND LIABILITY Seller warrants that this product under normal use and service as described in the operator s manual shall be free from defects in workmanship and material for a period of twelve 12 months from the date of shipment to the customer This limited warranty is subject to the following exclusions Batteries hot wire or hot film sensors and certain other components when indicated in specifications are warranted for a period of 90 days from the date of shipment to the customer With respect to any repair services rendered seller warrants that the parts repaired or replaced will be free from defects in workmanship and material under normal use for a period of 90 days from the date of shipment to the customer Seller does not provide any warranty on finished goods manufactured by others Only the original manufacturer s warranty applies Unless specifically auth
16. P switches with numbers corresponding to values Adjusting Mass Sensitivity 53 54 As you look at the DIP switches the leftmost switch has the value of 0 00001 the next has the value of 0 00002 etc as shown in the diagram above The factory calibrated setting of the DIP switches should be 00278 mg m Hz To obtain this value make the following setting TELON Figure B 3 DIP switches set to On and Off at the factory for a setting of 0 00278 mg m gt Hz setting Study this diagram Note that to obtain 0 00008 the 0 00008 switch is on to obtain 0 0007 the 0 0004 0 0002 and 0 0001 switches are on to obtain the 0 002 the 0 002 switch is on You can see that the buttons are additive and total 0 00278 The maximum sensitivity that can be set using the DIP switches is 0 00399 If a higher sensitivity is needed the two pairs of vertical holes on the right side of the DIP switches can be activated to give 0 004 and 0 008 To activate them connect together the first two holes or the second two holes Figure B 2 Appendix B Appendix C Specifications Mass concentration range 0 01 to 10 mg m Particle size range 0 01 um to 10 um Sample flow range 1 0 L min Sensitivity 0 001 mg m Accuracy 10 of reading or 0 01 mg m Display 4 digits Temperature limits Concentration XX XX mg m Frequency XXXX Hz 41 F to 104 F Measuring time 5 C to 40 C Switch selectable 24 or 12
17. RENT Indicator Sensor cleaning dial Precipitator NEEDLE Aerosol Inlet Sponge Compartment Door Chapter 1 Preparing the Piezobalance for Operation Installing the Impactor Set Up ee Sas Figure 3 Back of PIEZOBALANCE 17 Pull Up Locks 18 Battery Charge Port The following paragraphs give step by step instructions for preparing the PIEZOBALANCE for operation All steps must be completed to ensure proper operation of your instrument An impactor is used on the inlet of the PIEZOBALANCE to remove nonrespirable particles from the air being sampled You must install it before running the instrument To install the impactor follow these five steps Step 1 Locate the impactor assembly in the triangular compartment in the carrying case Figure 4 Figure 4 Impactor assembly Step 2 Remove the aerosol inlet sidepanel of the PIEZOBALANCE by pulling up on the small nylon locks Figure 5 Step 3 To install the impactor push the exit of the impactor into the inlet of the PIEZOBALANCE located right of center Figure 6 The impactor is properly installed when the screw hole on the PIEZOBALANCE coincides with the cutaway area of the impactor assembly Figure 6 Installing the impactor Chapter 1 Filling the Sponge Preparation Bottles Preparing the Sensor Cleaning Sponges Set Up Step 4 With the impactor in place install the mounting thumbscrew Figure 7 Step 5 Attach the sidepanel to th
18. RY VOLTAGE 11 Figure 12 displays the charge level of the batteries When the PWR button is pressed the needle should read well in the center of the blue region PRECIPITATOR CURRENT 12 Figure 12 displays the current level of the precipitator Within a couple seconds of pressing the MEAS button the needle should read well in the center of the black region Sensor cleaning dial 13 Figure 12 controls the placement of the detergent sponge and rinse sponge for cleaning the sensor NEEDLE O S 14 Figure 12 indicates the position of the precipitator needle The precipitator needle should be in the open O position for removal It should be in the shut S position for operation Aerosol Inlet 15 Figure 12 is where the aerosol to be measured is drawn into the PIEZOBALANCE The inlet contains an impactor to eliminate particles above the impactor cut size The instrument is shipped standard with a 3 5 micron impactor Pull Up Locks 16 Figure 13 make it easy to remove the side panel Chapter 2 Sponge Compartment Door 17 Figure 13 can be removed easily to give you access to the sponge tray for cleaning or rewetting the sponges The Basic Frequency and mass sensitivity of the PIEZOBALANCE is posted on the inside of this door Battery Charge Port 18 Figure 13 allows the battery charger to be plugged into the PIEZOBALANCE Figure 13 Parts and functions of PIEZOBALANCE Description of Parts and Functions 15 16 C
19. Stepl Remove the side and end panels of the PIEZOBALANCE that cover the pump Figure 33 Figure 33 Removing the panels Step2 Using the offset screwdriver remove the two screws that connect the pump bracket to the PIEZOBALANCE Figure 34 Figure 34 Removing the screws that connect the bracket to the PIEZOBALANCE Chapter 4 Step 3 Disconnect the pump s intake hose so that the pump and bracket assembly can be removed from the instrument Figure 35 Figure 35 Removing the intake hose Step 4 Remove the three screws on the exhaust side of the pump that connect the pump to the bracket Step 5 Remove the O ring and use the pin vise provided to pull the pump rotor out of the housing Figure 36 The four carbon vanes should fall out of the rotor If this method does not work use the alternate method that follows Maintenance 37 38 Alternate method Remove the screws that attach the motor to the pump Gently push on the center shaft of the pump until the rotor comes out the other end Step 6 Place the rotor and carbon vanes in a beaker of grease solvent Figure 37 Caution Do not put the bearings in the grease solvent This will inhibit the operation of the pump Figure 37 Soaking the rotor and carbon vanes Step 7 After soaking the rotor and vanes dry them thoroughly Step 8 Wipe off the bearings with a soft dry cloth Step 9 Clean the inside of the housing with a cotton swab or s
20. aerosol then reset sensitivity Check calibration by making sure PIEZOBALANCE and filter measure same aerosol then reset sensitivity Ensure only dry particles are being sampled Use longer sample time Clean and thoroughly dry the sensor Allow time for the instrument to equilibriate to ambient temperature Find an area without decreasing humidity Allow sensor to dry Chapter 5 Overall System Appendix A Theory of Operation A schematic of the PIEZOBALANCE is shown in Figure A 1 Aerosol enters through the inlet and passes into the impactor Ideally with the standard 3 5 micrometer impactor particles having aerodynamic diameters greater than 3 5 micrometers strike the impaction surface while particles smaller than 3 5 micrometers exit the impactor and pass through a short transport tube to the precipitator In fact the impactor s cut off range is not perfect and some particles greater than 3 5 micrometers pass through the impactor while some particles smaller than 3 5 micrometers strike the impaction surface At 3 5 micrometers 50 percent of the particles should impact out while 50 percent should pass through inlet Figure A 1 Schematic of the PIEZOBALANCE In the precipitator the aerosol passes axially along the precipitator needle and through a nozzle that forces the particles through the high intensity portion of the corona discharge The negative polarity corona discharge passing from needle
21. ations NOS OIPOMNH PEP WWWWWWWWWWNNNNNNNNNN RRR PRR RR Re NRF CUOANDOWPWNFODOUOANDOUBPWNFOUOANDUTUFPWNF COO A 1 A 2 Troubleshooting Theory of Operation Mass Sensitivity Specifications Assembly Drawing PIEZOBALANCE and accessories Front of PIEZOBALANCE Back of PIEZOBALANCE Impactor assembly Removing the side panel Installing the impactor Installing the thumbscrew Using the Sponge squeezer to remove excess water Sponge tray with sponges Removing the sponge compartment door Installing the sponge tray Parts and functions of the PIEZOBALANCE Parts and functions of PIEZOBALANCE Selecting the Measurement Time Checking the battery voltage Comparing the sensor frequency with the Basic Frequency Checking the precipitator current level Concentration of respirable aerosol displayed for 24 second sample Opening the sponge compartment door Removing the sponge tray Rinse and Detergent sponges Using the sponge squeezer to remove excess water Sensor in the soak position The sensor in the drying position Sensor cleaning dial turned 10 degrees Clean the sensor with the swab Cleaning the sensor with the fast method Charging the Battery Pack Removing the inlet panel Removing the impactor and housing Impactor and housing Removing the precipitator needle assembly Removing the panels Removing the screws that connect the bracket to the PIEZOBALANCE Removing the intake hose Removing the pump rotor and vanes Soaking t
22. d to the concentration displayed is determined in the factory by calibrating the instrument through filter sampling In factory calibration the PIEZOBALANCE measures an aerosol concentration that is also collected by filters and weighed The mass concentration is defined by equation 1 1Df Bee 1 SQ Dt Where C Mass concentration in mg m Df Change in frequency Hz S Sensitivity Hz mg Q Flow rate m sec Dt Time of sample sec A more direct calculation combines part of Equation 1 into a single number P as defined in Equation 2 1 P 2 DtSQ Where P PIEZOBALANCE sensitivity mg m Hz where the frequency in hertz is taken for a 120 second sample The concentration can then be described by Equation 3 C P Df 3 The values of the sensitivities P and S described above must be determined by calibration The mass sensitivity of the PIEZOBALANCE is very stable over a wide range of aerosols and conditions The mass sensitivity S of the PIEZOBALANCE has been determined to be 180 hertz per microgram for general environments such as industrial dusts fumes mists smokes and aerosols Using S 180 Hz ug P is calculated as 0 00278 mg m Hz This is the setting for PIEZOBALANCE sensitivity used at the factory 51 52 Fractional Component Testing 8 Hour Average Exposure Testing Applications The mass sensitivity of the PIEZOBALANCE can be adjusted to meet specific needs It can be adjusted
23. defective instruments are as detrimental to TSI as they are to our customers our service policy is designed to give prompt attention to any problems If any malfunction is discovered please contact your nearest sales office or representative or call TSI s Customer Service department at 612 483 4711 Chapters Contents About this manual Introduction I Set up Unpacking Il HI IV Parts Identification Preparing the Piezobalance for Operation Installing the Impactor Filling the Sponge Preparation Bottles Preparing the Sensor Cleaning Sponges Description of Parts and Functions Control Panel Data Display Operational Pushbuttons Range Selector Operation Monitor Miscellaneous Features Operation Selecting the Measurement Time Making a Measurement Approximate guidelines for Sensor Cleaning Special Applications Low Concentration Measurements High Concentration Measurements Maintenance Maintenance Schedule Cleaning and Rewetting the Sensor Cleaning Sponges Cleaning the Sensor Stubborn Deposits Patient Method Fast Method Battery Charging Removing and Greasing the Impactor Cleaning the Precipitator s Needle Assembly Vacuum Pump Removing and Cleaning the Vacuum Pump Checking for Air Leaks Checking the Flow Rate Adjusting the Flow Rate OONNA UM 13 13 14 14 14 14 17 18 21 21 21 22 25 25 25 28 29 29 30 32 32 34 35 35 40 41 42 lt Appendices uns Illustr
24. detected The sensor frequency is effectively reduced to a more convenient range 1 to 3 kilohertz by electrically mixing the sensor frequency against a reference crystal having a resonant frequency that is 1 to 3 kilohertz higher than the sensor frequency The resulting mixed frequency is equal to the difference between reference crystal and sensor crystal frequencies The mass concentration is then calculated as C f2 f1 StQ 4 Where C Aerosol concentration in mg m t Sample measurement time in seconds f Mixed crystal frequency at time 0 Hz f Mixed crystal frequency at time t Hz Q Volumetric air sampling rate m3 sec S Mass sensitivity of the crystal sensor Hz microgram For the sensor described by Equation 3 with an aerosol flow rate of 1 liter per minute C 0 333 h A t 5 Theory of Operation 49 50 Circuitry Figure A 5 shows the electronic block diagram for both the primary and reference crystals which are driven by separate electronic circuits The frequency signals from the two driving circuits enter a frequency mixer that electrically subtracts the two frequency signals and generates a beat frequency The beat frequency is the output frequency signal of the piezoelectric microbalance Figure A 5 Block diagram of electronic system Appendix A Theory Appendix B Adjusting Mass Sensitivity The mass sensitivity of the PIEZOBALANCE which relates the frequency measure
25. e 40 drops of detergent on the detergent sponge Step 9 Place 5 to 8 drops of clean water on the rinsing sponge Step 10 Slide the sponge tray back into the PIEZOBALANCE until you hear a click The click means the tray is locked in place Replace the sponge compartment door 27 Cleaning the Clean the sensor when the sensor check indicates it is required that is when the Sensor base frequency is more than 1000 Hz higher than the Basic Frequency To clean the sensor follow these six steps Step 1 Step 2 Step 3 Make sure the sponges are clean and suitably damp If needed perform the steps in Cleaning and Rewetting Sensor cleaning Sponges Press the PWR CHK and STRT buttons Slowly rotate the sensor cleaning dial in the clockwise direction until it reaches the first WAIT position 4 o clock Stop at this position for 20 seconds Here the sensor is being soaked by the detergent sponge Figure 23 Caution Never engage the MEAS button while a cleaning cycle is in progress Doing so will damage the precipitator needle Step 4 Figure 23 Sensor in the soak position Continue to rotate the knob clockwise until it stops 10 o clock Now rotate the knob slowly counterclockwise until you reach the second WAIT position 2 o clock Stop at this position for one minute Here the sensor is drying Figure 24 Chapter 4 Figure 24 The sensor in the drying position Step 5 With a firm and rapid twist continue
26. e PIEZOBALANCE The carrying case also contains two small drop bottles Fill one of these with the cleaning solution supplied in the carrying case in a large squeeze bottle and fill the other with distilled water These will be used for sponge cleaning and preparation Label the bottles To make measurements the PIEZOBALANCE collects particles on its sensor These particles must be cleaned from time to time as indicated by the instrument To do so the sensor cleaning sponges must be in the proper condition To ensure that they are ready for cleaning the sensor follow these eight steps Step 1 Locate the plastic sponge cassettes sponges and sponge squeezer in the carrying case Remove one cassette two sponges and the sponge squeezer Step 2 Wash the sponges with lukewarm tap water Step 3 Squeeze out the excess water using the sponge squeezer Figure 8 10 Figure 8 Using the Sponge squeezer to remove excess water Step 4 Place the sponges in the plastic cassette tray Be sure they are flat and fill their compartment see Figure 9 Step 5 Place 40 drops of detergent supplied in the carrying case on the detergent sponge the sponge farthest from the tray handle Figure 9 Figure 9 Sponge tray with sponges Chapter 1 Step 6 Place 5 to 8 drops of distilled water on the rinsing sponge the sponge closest to the tray handle Step 7 Locate the small sponge compartment door on the PIEZOBALANCE Figure 10
27. encies in rapid succession Step 6 After the first frequency is displayed record the frequencies displayed every two seconds except the first which should be near the Basic Frequency Record a total of five or six frequencies Because the 24 second measurement time is being used remember to multiply each reading by 5 Step 7 Check the data you have recorded The frequencies should increase steadily Example 100 Hz 206 Hz 302 Hz 396 Hz 505 Hz etc Chapter 3 Operation Do not include more than 10 seconds of data five readings unless the frequencies are increasing steadily Step 8 To calculate the respirable aerosol mass concentration use the following equation f C 0 333 mg m 2 t Where C Respirable aerosol concentration in mg m3 t Sample measurement time in seconds this is the number of readings x 2 f Highest frequency obtained steadily Hz From the data of the 10 second total sample given above the concentration would be calculated as 505 C 0 333 mg m3 16 8 mg m3 2 10 23 24 Chapter 3 Maintenance Schedule Cleaning and Rewetting the Sensor cleaning Sponges Chapter 4 Maintenance If you follow the maintenance schedule given below the PIEZOBALANCE and its accessories will provide accurate and reliable measurements for years Daily 1 Check the sensor cleaning sponges to ensure that they are clean and suitably damp so that the sens
28. ensor as long as the MEAS button is depressed and the PWR button is on If you leave the MEAS button on between tests you must clean the sensor more often Step 10 To make another measurement push the MEAS button and then the STRT button When you are finished making measurements push the PWR button to switch off the instrument Chapter 3 Approximate Guidelines for Sensor Cleaning The following table gives approximate guidelines for the number of measurements which can be made with various mass concentrations before sensor cleaning is necessary This is only an approximation The sensor should always be cleaned if the base frequency is 1000 hertz or more above the Basic Frequency Continuous Measurements Before Concentration Measuring Time Cleaning using 24 second measurement time Special Applications Low Concentration Measurements Operation The following sections explain how the PIEZOBALANCE can be used for making very low or very high mass concentration measurements for special applications To accurately measure low concentrations from 0 005 to 0 05 mg m an extended measuring time is necessary You will need a stopwatch pencil and paper Carefully follow these nine steps Step 1 Clean the sensor Step 2 Select the 120 second time Step 3 Press the PWR button Step 4 Press the MEAS button Step 5 Simultaneously press the STRT button and start the stopwatch Step 6 After 2 seconds
29. hapter 2 Selecting the Measurement Time Chapter 3 Operation Operation of the PIEZOBALANCE is simple This section explains how to use the PIEZOBALANCE step by step to make mass concentration measurements A standard measurement consists of 1 ensuring that the sensor s base frequency is within 1000 Hz of the Basic Frequency and cleaning the sensor if necessary and 2 taking the measurement To select the measurement sample time press the MEAS TIME button on the front panel to the desired position out for 120 seconds and in for 24 seconds Figure 14 Figure 14 Selecting the Measurement Time Use the 120 second time to measure particle concentrations from 0 01 to 3 0 milligrams per cubic meter Use the 24 second time to measure particle concentrations from 2 to 10 milligrams per cubic meter The advantage of the shorter time is that it reduces the frequency of sensor cleaning by reducing mass build up on the sensor If you are unsure of the concentration being measured start with the 120 second time and use this initial measurement to determine which time to use If the resultant measurement of mass concentration is greater than 3 0 and less than 10 0 milligrams per cubic meter use the 24 second time if the measurement is between 2 and 3 milligrams per cubic meter select either time 17 After several more measurements are made you may want to change your choice to coincide with the range you use most often If most
30. he rotor and carbon vanes Cleaning the inside of the pump housing Exploded drawing of the pump Leak checking the PIEZOBALANCE Using a bubble flow meter Adjusting the flow rate Schematic of the PIEZOBALANCE Piezoelectric microbalance technique before sampling A 3 A 4 A 5 B 1 B 2 B 3 Piezoelectric microbalance technique after sampling Schematic of the impactor Block diagram of electronic system Location of DIP switches Schematic of DIP switches with numbers corresponding to values DIP switches set to On and Off at the factory for a setting of 0 000278 mg m gt Hz setting 46 47 50 53 53 54 iii iv About This Manual The PIEZOBALANCE Operation and Service Manual tells you how to operate and maintain the PIEZOBALANCE Read it thoroughly before using the instrument Chapter 1 explains how to set up the PIEZOBALANCE Chapter 2 describes the parts of the PIEZOBALANCE and how they work Chapter 3 explains how to operate the PIEZOBALANCE Chapter 4 covers the maintenance schedule and procedures required to keep the PIEZOBALANCE operating properly Chapter 5 provides a troubleshooting table for quick reference Appendix A describes the theory of operation on which the instrument is based Appendix B explains the theory of mass sensitivity and how to set the mass sensitivity of the PIEZOBALANCE Appendix C lists the instrument s important specifications References to operational buttons on the PIEZOBALANCE
31. ncy of the sensor was not steadily increasing The concentration is too low for the current sampling time and a longer sampling time is required Operational Pushbuttons Range Selector Operation Monitor Other Features The functions of the four operational pushbuttons on the control panel 5 Figure 12 are explained below PWR Pushbutton 6 Figure 12 starts the vacuum pump in the PIEZOBALANCE and powers up the entire unit STRT Pushbutton 7 Figure 12 starts a mass concentration measurement if MEAS button is already depressed or a Basic Frequency check if CHK button is already depressed MEAS Pushbutton 8 Figure 12 activates the electrostatic precipitator The entire time the MEAS button is depressed aerosol is being collected on the sensor The precipitator current needle should rise slowly and stop in the middle of the Operation Monitor after depressing the MEAS button CHK Pushbutton 9 Figure 12 which is short for sensor check displays the sensor s base frequency The base frequency should be compared to the Basic Frequency periodically to determine if the sensor needs to be cleaned MEAS TIME Button 10 Figure 12 enables you to select either a 24 second or 120 second measurement time The Operation Monitor serves two purposes According to the status of the Operational Pushbuttons the monitor displays either the battery s charge level or the precipitator s current level as described below BATTE
32. of the crystal between the flat surfaces of the plate like crystal No node exists on the surface where particles are weighed Only the portion of the crystal between the electrodes vibrates The sensor then detects only those particles that stick to the electrode surface Particles sticking to the surface of the quartz outside the electrode area have a negligible effect on the vibrating portion of the crystal and are not detected Appendix A A given mass of particles sticking to the electrode of a given crystal causes a downward shift in natural vibrational frequency The simplified relationship between added mass and natural frequency for AT cut quartz crystals is Df 2 27 f 2 A DM 2 Where Df Change in natural frequency Hz f Natural vibrational frequency of the crystal MHz A Electrode area of crystal cm DM Mass added to electrode area micrograms If the frequency shift Df is sufficiently small in comparison to the natural frequency typically Df is less than 0 02 of f then Df is a linear function of the added mass DM given by Equation 2 The crystal sensor used in the PIEZOBALANCE has a nominal frequency of 5 MHz with 0 635 centimeter diameter electrodes The theoretical sensitivity of this sensor S Df DM is S 180 Hz microgram 3 Since a frequency shift of 1 hertz can easily be measured with the simple frequency counter in the PIEZOBALANCE a mass as low as approximately 0 005 microgram can be
33. oft cloth Be careful not to scratch the surface Figure 38 Chapter 4 Figure 38 Cleaning the inside of the pump housing Step 10 After all the parts are dry reassemble them in reverse order A clean O ring works well to hold the vanes in the rotor while reassembling See Figure 39 for an exploded drawing of the pump no 1502231 Figure 39 Exploded drawing of the pump Step 11 Check the PIEZOBALANCE for leaks Then check the sample flow rate and reset it if necessary See the following sections on Checking for Air Leaks and Checking The Flow Rate Maintenance 39 40 Checking for Check the system for air leaks before you check the pump s flow rate To leak Air Leaks Check the PIEZOBALANCE follow these five steps Step1 Attach a 40 centimeter flexible hose to the vacuum pump s exhaust Step 2 Place the other end of the house approximately 10 centimeters from your ear Figure 40 Caution For safety do not place too close to you ear Step 3 Press the PWR button you should hear a soft steady hum Step 4 Place your finger over the aerosol intake port of the PIEZOBALANCE The sound should now drop to a lower frequency If the pitch does not change the system has a leak Figure 40 Figure 40 Leak checking the PIEZOBALANCE If you are unsure about what you are hearing simulate aleak Turn the sensor cleaning dial to the 10 o clock position and repeat steps 1 through 4 Chapter 4 Step5 If you de
34. or follow these five steps Step 1 Remove the panel that contains the sampling inlet by pulling up on the small nylon locks Figure 29 Various impactors with different cut off sizes are available Chapter 4 Maintenance Figure 29 Removing the inlet panel Step2 Remove the impactor and housing by unscrewing the thumbscrew and pulling the assembly toward the right end of the cabinet Figure 30 Figure 30 Removing the impactor and housing Step 3 Remove the impactor from its housing by unscrewing the headscrew Figure 31 33 Figure 31 Impactor and housing Step4 Clean the surface of the impactor with a soft paper towel moistened with alcohol If you are using the instrument in very dusty conditions such as in a sawmill clean the impactor housing as well Blow clean compressed air through it Step 5 Apply a light coat of vacuum grease to the impactor s impaction surface Cleaning the Clean the precipitator needle every two weeks or whenever the precipitator Precipitator s Current proves unstable To clean the precipitator needle you will need the Assembly A small beaker Cleaning solution supplied Clean compressed air Follow these seven steps Stepl Turn the tick mark on the precipitator needle assembly to the O open position Step 2 Pull the needle assembly straight out until the entire needle assembly is clear of the PIEZOBALANCE Figure 32 Caution The large screwdrive
35. or can be cleaned effectively 2 Recharge the batteries 3 Check the impactor clean and grease if necessary Weekly Clean both sensor sponges thoroughly Every 2 Weeks Clean the precipitator needle assembly Every Month Check the pump for leaks Every Six Months 1 Clean the vacuum pump 2 Check the rate of airflow Yearly Return the PIEZOBALANCE to TSI Incorporated for a complete cleaning checkout and recalibration The sensor cleaning sponges must be prepared before the sensor can be cleaned To prepare the sponges follow these 10 steps Step1 Open the sponge compartment door on the side of the instrument Figure 19 25 26 Figure 19 Opening the sponge compartment door Step2 Pullthe sponge tray straight out Figure 20 Figure 20 Removing the sponge tray Step2 Moisten the sponges with tap water to prepare them for removal Never try to remove dry sponges or you will damage them Step 3 Remove the rinsing sponge the one closest to the tray handle Figure 21 Chapter 4 Maintenance Figure 21 Rinse and Detergent sponges Step4 Rinse the sponge with lukewarm water Step 5 Squeeze out excess water from the sponge using the sponge squeezer Figure 22 Figure 22 Using the sponge squeezer to remove excess water Step 6 Return the sponge to its tray Step 7 Repeat steps 3 thru 6 with the detergent sponge the sponge farthest from the tray handle Step 8 Plac
36. orized in a separate writing by seller seller makes no warranty with respect to and shall have no liability in connection with any goods which are incorporated into other products or equipment by the Buyer The foregoing is IN LIEU OF all other warranties and is subject to the conditions and LIMITATIONS stated herein NO OTHER EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR PARTICULAR PURPOSE OR MERCHANTABILITY IS MADE THE EXCLUSIVE REMEDY OF THE USER OR PURCHASER AND THE LIMIT OF THE LIABILITY OF SELLER FOR ANY AND ALL LOSSES INJURIES OR DAMAGES IN CONNECTION WITH THIS PRODUCT INCLUDING CLAIMS BASED ON CONTRACT NEGLIGENCE STRICT LIABILITY OTHER TORT OR OTHERWISE SHALL BE THE RETURN OF THE PRODUCT TO THE FACTORY OR DESIGNATED LOCATION AND THE REFUND OF THE PURCHASE PRICE OR AT THE OPTION OF SELLER THE REPAIR OR REPLACEMENT OF THE PRODUCT IN NO EVENT SHALL SELLER BE LIABLE FOR ANY SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES NO ACTION REGARDLESS OF FORM MAY BE BROUGHT AGAINST THE SELLER MORE THAN ONE YEAR AFTER THE CAUSE OF ACTION HAS ACCRUED The purchaser and all users are deemed to have accepted the terms of this LIMITATION OF WARRANTY AND LIABILITY which contains the complete and exclusive limited warranty of seller This LIMITATION OF WARRANTY AND LIABILITY may not be amended or modified nor may any of its terms be waived except by a writing signed by an authorized representative of seller Service Policy Knowing that inoperative or
37. r slot in the center of the knob does not control the locking or unlocking of the needle assembly Do not turn this screw 34 Chapter 4 Figure 32 Removing the precipitator needle assembly Step3 Place the needle assembly in a beaker tip down Step4 Fillthe beaker with cleaning solution up to the first O ring level about 13 mm 1 2 in Step5 Forroutine cleaning soak the sensor for several minutes for tougher deposits soak the precipitator needle overnight Step6 Rinse the assembly in hot tap water and blow it dry with clean compressed air or allow it to air dry Step 7 Carefully insert the assembly back into the PIEZOBALANCE by aligning the key slot and pushing straight in When the needle is in place turn the knob to the S shut position Vacuum Pump Clean the vacuum pump every six months if it sounds loud and erratic clean it sooner After you clean and reinstall the pump check the system for air leaks Then check the flow rate and adjust it as needed The following sections explain in detail how to perform each of these steps Removing and To remove and clean the pump you need the following equipment Cleaning the Pump Offset Phillips head screwdriver provided A small beaker A cotton swab A soft cloth A good grease solvent Maintenance 35 36 Before you clean the pump you must remove it from the instrument Follow the 11 steps below for both removing and cleaning the pump
38. ss of the collected particles This frequency difference is referred to as f final frequency time t gt Figure A 3 Piezoelectric microbalance technique after sampling Appendix A The particle concentration is calculated easily by the following formula C 0 333 SS mg m 1 Where C Aerosol concentration in mg m Sample measurement time in seconds this is the number of readings x 2 f Frequency read at beginning of measurement Hz Frequency read at end of measurement Hz LE Il m N Il The operation of the impactor precipitator piezoelectric microbalance and circuitry is explained individually below Impactor Impactors operate under a simple principle if a stream of particle laden air is directed at a surface particles with sufficient inertia will impact on the surface while smaller particles and therefore insufficient inertia will follow the air streamlines and not be collected See Figure A 4 An impactor consists of a nozzle either round or rectangular and an impaction plate trajectory of impaction impacted particle particle too plate small to impact Figure A 4 Schematic of the impactor Ideally an impactor would collect all particles above its cut off diameter while smaller particles would follow the air streamlines around the impaction surface and pass through the impactor However the cut off in the impactor is not perfect and some particles greater than the cut off diameter
39. t Clean precipitator needle assembly Battery voltage is too low or Battery is discharged Charge battery for 15 hours until unstable fully charged Full battery charge lasts less Battery is dead Replace batteries than four hours Clean the pump and check flow rate as described in Maintenance 43 44 Symptom Consecutive mass measurements fluctuate too much Measurements do not agree with filter measurements Negative light comes on during or after measurement Possible Causes Aerosol concentration fluctuates Sensor is dirty Relative humidity or temperature fluctuates too rapidly Precipitator needle assembly is dirty Impactor is dirty Pump is dirty Sample time is too short Filter and PIEZOBALANCE are not measuring the same aerosol PIEZOBALANCE sensitivity to the specific aerosol is different from set sensitivity Deposited particles are evaporating Concentration is so low that it is within noise level of the sensor Sensor not cleaned well Moisture on sensor Solution Use a plenum chamber to dampen aerosol humidity or temperature fluctuations Clean sensor Use a plenum chamber to dampen aerosol humidity or temperature fluctuations Clean precipitator needle assembly see Maintenance Clean the impactor see Maintenance Clean the pump see Maintenance Use longer sample times Check calibration by making sure PIEZOBALANCE and filter measure same
40. tect a leak make sure that the Sensor knob is firmly in 12 o clock position O rings are in good condition in the impactor between the sensor mounting block and the precipitator housing in the precipitator needle assembly in the vacuum pump Checking the After you clean the pump and leak check the PIEZOBALANCE check the flow Flow Rate ate Follow these two steps Step1 Connect an accurate airflow meter to the inlet of the impactor Any flow meter will work that has a pressure drop of 1 cm H O or less at a flow of 1 liter per minute If a flow meter is unavailable use a bubble flow meter and stopwatch Figure 41 Figure 41 Using a bubble flow meter Maintenance 41 42 Adjusting the Flow Rate Step2 Measure the flow rate with the power on and the sensor cleaning knob in the 12 o clock potition The flow rate should be 1 00 0 05 liters per minute If the flow rate needs adjustment follow the instructions given in the following section under Adjusting the flow rate If the flow rate check indicates that the flow rate should be adjusted perform the following four steps Stepl Remove the sidepanel of the PIEZOBALANCE that contains the battery charge port Step2 Locate the pump adjustment circuit on the right hand side of the PIEZOBALANCE Figure 42 Step3 Adjust the flow rate by turning the coarse or fine adjustment potentiometers on the pump adjustment circuit as shown in the Figure 41
41. tivity current mass Sensitivity x X For example the average 8 hour exposure level is known to be 0 5 milligrams per cubic meter of respirable dust The PIEZOBALANCE with its standard 3 5 microgram impactor is used to take random samples during an 8 hour period The average of these samples is calculated as 0 3 milligrams per cubic meter In this case The sensitivity would then be adjusted to 1 67 x the current level of sensitivity If the current level of sensitivity is the factory standard of 00278 milligrams per cubic meter then the new sensitivity setting would be 00278 x 1 67 0 00464 milligrams per cubic meter Appendix B Non standard If you want to measure nonstandard aerosols such as cotton dust you can aerosols Adjust the mass sensitivity of the instrument To determine what the mass sensitivity of the instrument should be for different aerosols perform calibration testing How to Set The mass sensitivity can be easily set with DIP switches To reset the mass Mass Sensitivity sensitivity follow these 3 steps Step 1 Remove the side panel on the side of the instrument that stores the batterypack Step 2 Locate the row of DIP switches on the back side of the control panel righthand side Figure B 1 Figure B 1 Location of DIP switches Step 3 Referring to Figure B 2 for the values for each of the DIP switches set the DIP switches ON and OFF as needed 1 2 3 4 5 6 7 8 9 10 Figure B 2 Schematic of DI
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