Model 3741B1230G DC Response Accelerometer Installation and
Contents
1. TO ALLOW MOTION WITHOUT PULLING CABLE TYPE PETRO WAX OR 2 3 51 76 3 4 76 89 BEER EQUIVALENT TYPICAL m a SE xxx gt dide o se WLLL LL TEST STRUCTURE C sommeone w Ya DIMENSIONS IN INCHES DIMENSIONS IN MILLIMETERS IN BRACKETS SE rafy T 728m gt FASTEN CABLE TO TEST STRUCTURE TYPICALLY WITHIN 2 3 51 76 OF SENSOR THEN FASTEN AGAIN WITHIN 3 4 76 101 E omm 3425 WALDEN AVE DEPEW NY 14043 DECIMALS 01 DECIMALS X 03 716 684 0001 E MAIL sales8pcb OF PREVIOUS ATTACHMENT BETWEEN THE TEST STRUCTURE AND A FIXED STRUCTURE ALLOW A SERVICE LOOP LARGE XXX 4 005 XX 0 13 INSTALLATION DRAWING 716 684 MAIL Salesgepcb com ENOUGH TO PREVENT PULLING OF THE CABLE WHEN SHAKING MORE ATTACHMENT POINTS WILL PROVIDE LESS ANGLES 2 DEGREES ANGLES 2 DEGREES DWG NO MODEL 3741 SERIES is NOISE IN THE RESULTING DATA LOOSE CABLES OR PARTS ELSEWHERE ON THE TEST STRUCTURE CAN ALSO GENERATE IDENT NO 50864 NOISE ON THE SIGNAL RECEIVED FROM THE MODEL 3741 SERIES DC ACCELEROMETER 5268 003 005 0 07 0 13 SHEET 20F2 1 4 3 22. a timely fashion 8 2 BACK TO BACK CALIBRATION THEORY Many companies choose to purchase the equipment necessary to perform the recalibration procedure in house While this may result in both a savings of time and money it has also been attributed to incorrect readings and costly errors Therefore in an effort to prevent the common mistakes associated with customer performed calibration this document includes a broad overview of the Back to Back Calibration technique This technique provides a quick and easy method for determining the sensitivity of a test accelerometer over a wide frequency range Back to Back Calibration is perhaps the most common method for determining the sensitivity of piezoresistive accelerometers This method relies on a simple comparison to a previously calibrated accelerometer typically referred to as a reference standard Signal out Mount test sensor to this end Mount this end to exciter d AC Sensing Element Figure 9 Reference Standard Accelerometer These high accuracy devices which are directly traceable to a recognized standards laboratory are designed for stability as well as configured to accept a test accelerometer By mounting a test accelerometer to the reference standard and then connecting this combination to a suitable vibration source it is possible to vibrate both d
3. connected in a Wheatstone bridge circuit The integral amplifier provides a low impedance output to follow on instrumentation These particular accelerometers provide a dc or steady state acceleration measurement capability as opposed to a predetermined low frequency cut off associated with charge or ICP type accelerometers Examples where High Sensitivity DC accelerometers may be used e Automotive Crash Simulation Sleds e Automotive Road Load Rigs e Aircraft Flutter Load Testing e Whole Body Vibration Studies Lower range higher sensitivity DC accelerometers allow for simple 2 g turn over testing as a means of determining the health of the unit prior to use By simply placing the unit in a 1g position and noting the output then turning the unit on its side to the null position and noting the Og output error followed by the same technique only in the lg position the user can verify the health of the accelerometer The 10 null and 1g values are now apparent to the user General High Sensitivity DC Accelerometer Terms Excitation 10 V dc typical Allowable excitation range 46 to 430 Vdc Sensitivity mV g ZMO Zero Measurand Output mV output with no acceleration applied TSS Thermal Sensitivity Shift sensitivity variation due to temperature change TZS Thermal Zero Shift ZMO variation due to temperature change Resolution Minimum acceleration measurement level based on output sensitivity and in
4. migrate into devices that are not hermetically sealed Such devices should only be wiped with a dampened cloth and never submerged or have liquids poured upon them Repair In the event that equipment becomes damaged or ceases to operate arrangements should be made to return the equipment to PCB Piezotronics for repair User servicing or repair is not recommended and if attempted may void the factory warranty Calibration Routine calibration of sensors and associated instrumentation is recommended as this helps build confidence in measurement accuracy and acquired data Equipment calibration cycles are typically established by the users own quality regimen When in doubt about a calibration cycle a good rule of thumb is to recalibrate on an annual basis It is also good practice to recalibrate after exposure to any severe temperature extreme shock load or other environmental influence or prior to any critical test PCB Piezotronics maintains an ISO 9001 certified metrology laboratory and offers calibration services which are accredited by A2LA to ISO IEC 17025 with full traceablility to N LS T In addition to the normally supplied calibration special testing is also available such as sensitivity at elevated or cryogenic temperatures phase response extended high low frequency response extended range leak testing hydrostatic pressure testing and others For information on standard recalibration serv
5. 1529 PIEZOTRONICS Model 3741812306 DC Response Accelerometer Installation and Operating Manual For assistance with the operation of this product contact PCB Piezotronics Inc Toll free 800 828 8840 24 hour SensorLine 716 684 0001 Fax 716 684 0987 rotat customer aa action E mail info pcb com Satist Web www pcb com opcB peo 2s E PCB PIEZOTRONICS A PCB GROUP COMPANY Warranty Service Repair and Return Policies and Instructions The information contained in this document supersedes all similar information that may be found elsewhere in this manual Total Customer Satisfaction PCB Piezotronics guarantees Total Customer Satisfaction If at any time for any reason you are not completely satisfied with any PCB product PCB will repair replace or exchange it at no charge You may also choose to have your purchase price refunded in lieu of the repair replacement or exchange of the product Service Due to the sophisticated nature of sensors and associated instrumentation provided by PCB Piezotronics user servicing or repair is not recommended and if attempted may void the factory warranty Routine maintenance such as the cleaning of electrical connectors housings and mounting surfaces with solutions and techniques that will not harm the physical material of construction is acceptable Caution should be observed to insure that liquids are not permitted to
6. 5 um sec2 NHz gt 108 Ohm Anodized Aluminum Epoxy 7 62 mm x 25 4 mm x 21 6 mm 9 92 gm Integral Cable Side Pigtail Ends 010 4 cond Shielded 3m Through Holes 2 NOTES 1 Offset tolerance is based on manufacturers supplied cable length 2 Typical 3 Case and shield to mounting surface or cable leads 4 65 to 250 F ref 75 F 54 to 121 C ref 24 C 5 FSO Full Scale Output over the Measurement Range 4VDC 6 Measured at 100 Hz 1 grms 7 Zero based least squares straight line method 8 See PCB Declaration of Conformance PS027 for details SUPPLIED ACCESSORIES Model 081A103 Mounting screw 2 Model ACS 103 Phase and Amplitude Calibration from 2 Hz to 5 of frequency range 1 Model M081A103 Mounting screw and washer M3 x 0 5 thread 2 OPTIONAL ACCESSORIES Model 080A208 Triaxial mounting block Entered AP Engineer RPF Sales RWM Approved BAM Spec Number Date 7 31 2012 Date 7 31 2012 Date 7 31 2012 Date 7 31 2012 46223 PCB PIEZOTROMCS Fa Ties onan Fax 716 684 0987 3425 Walden Avenue Depew NY 14043 E Mail info pcb com 4 3 2 1 the information disclosed hereon Neither it nor any REVISIONS without the written consent of PCB Piezotronics Inc REV DESCRIPTION DIN RELEASED TO DRAFTING 36402 CABLE TERMINATE TO PIGTAIL OUTPUT YELLOW OUTPUT WHITE POWER SIGNAL GROUND BLACK 2X 125 3 18 THRU POWER RED CONNECT TO DC VOLTAGE POWER
7. Adhesively mounted sensors often exhibit a reduction in high frequency range Generally smooth surfaces and stiff adhesives provide the best high frequency response METHOD 1 Adhesive Mounting Base This method involves attaching a base to the test structure then securing the sensor to the base This allows for easy removal of the accelerometer Contact the PCB factory representative for optional mounting plate details STEP 1 Prepare a smooth flat mounting surface A minimum surface finish of 32 pin 0 0008 mm generally works best STEP 2 Attach mounting screws of the sensor to the flat side of the appropriate adhesive mounting base according to the guidelines set forth in STEPS 2 and 3 of the Screw Mount Procedure presented above SCREW ATTACHMENT MODEL 3741 DC TORQUE TO PROPER ACCELEROMETER VALUE ADHESIVE MOUNTING BLOCK CN MOUNTING STRUCTURE FLAT WITH GOOD FINISH Figure 5 Mounting Base Adhesive Installation STEP 3 Place a small portion of adhesive on the underside of the mounting base block Firmly press down on the assembly to displace any extra adhesive remaining under the base When the accelerometer base block assembly is to be removed unscrew the accelerometer from its mounting base block prior to removal of base block from test article METHOD 2 Direct Adhesive Mount Caution It is recommended to use a mounting base with high sensitivity DC accel
8. SUPPLY SEE SPECIFICATION SHEET FOR PROPER EXCITATION VOLTAGE SHIELD MODEL 081A 103 CASE GROUND MOUNTING SCREW ASSEMBLY 2 SUPPLIED FOR M OPTION MODEL M081A103 BLACK ANODIZED OFF MOUNTING SCREW GROUND HOUSING ASSEMBLY 2 SUPPLIED 13 3 3 F MOUNTING HOLE PREPARATION FOR METRIC OPTION 089 2 26 V 22 5 6 MIN MOUNTING HOLE PREPARATION 4 40 UNC 2B 7 15 3 8 MIN 5 098 2 45 V 39 10 0 MIN M3 X 5 6H V 18 4 6 MIN SEE SHEET 2 OF 2 FOR CABLE STRAIN RELIEF INFORMATION LASER MARK PCB LOGO MODEL st UNIQUE SN XXX IN MODEL NUMBER INDICATES FS RANGE eg 3741B12200G SEISMIC MASS LOCATIONS ARE NOT MARKED o RECOMMENDED MOUNTING SURFACE SHOULD FLAT TO WITHIN 003 08 TIR DIMENSIONS IN INCHES cigar oe eee ae VvPCB PIEZOTRONICS OVER 51 32 33 34 WITH 32 08 FINISH FOR BEST RESULTS 3425 WALDEN AVE DEPEW NY 14043 XXX 005 XX 013 716 684 0001 E MAIL salesepcb com CG CENTER OF SEISMIC MEASUREMENT TOLERANCE 03 8 INSTALLATION DRAWING ANGLES 2 DEGREES ANGLES 2 DEGREES MODEL 3741 SERIES DWG NO 50864 RECOMMENDED MOUNTING TORQUE ON CAP SCREW 6 IN LBS 65 N CM mee Temm DC ACCELEROMETER 32661 1 4 3 2 4 3 2 1 PCB Piezotronics Inc claims proprietary rights in REVISIONS the information disclosed hereon Neither it nor any without the written consent of PCB Piezotronics Inc REV DESCRIPTION SEE SHEET ONE SERVICE LOOP
9. all applications Industrial applications often require shielded twisted pair cables to reduce the effects of EMI and RFI that is present near electrical motors and machinery Teflon jacketed cabling may be necessary to withstand corrosive environments and higher temperatures Feel free to contact a factory representative for a specific recommendation on cables that are best suited for your application STEP 2 Connect the cable to the accelerometer A small amount of thread locking compound placed on the connector threads prior to attachment helps secure the cable during testing In wet oily or dirty environments the connection can be sealed with silicone rubber sealant O rings and flexible heat shrink tubing Multi Conductor Cables Make accelerometer cable connection to appropriate connector plug via soldering or crimping leads to plug sockets Specific instructions for this activity are completely dependant on the plug required D sub circular Lemo Fischer etc to mate to follow on conditioning equipment s input receptacle Refer to instrumentation interface guidelines for proper mating of accelerometer cabling Pigtail Connections Certain high sensitivity DC accelerometers are provided with lightweight cables having Pigtail connections This type of connection reduces overall weight and incidence of connection intermittency under shock conditions In the event of a cable or connection failure the cables may be re
10. andard designed with a smooth flat mounting surface In addition to mounting the selection of the proper equipment is critical Some of the more important considerations include 1 the reference standard must be specified and previously calibrated over the frequency and or amplitude range of interest 2 the shaker should be selected to provide minimal transverse lateral motion and minimal distortion and 3 the quality of the meters signal generator and other devices should be selected so as to operate within the limits of permissible error 8 4 COMMON MISTAKES Most calibration errors are caused by simply overlooking some of the fundamental principals of dynamics This section attempts to address some of the more common concerns For stud mount sensors always mount the accelerometer directly to the reference standard Ensure that the mounting surfaces are smooth flat and free of any burrs Always use a coupling fluid such as silicone grease in the mounting interface to maintain a high mounting stiffness Mount the sensor according to the manufacturers recommended mounting torque Figure 13 Stud Mounting For adhesive mount sensors use a thin stiff layer of temporary adhesive such as quick bonding gel or superglue DO NOT use excessive amounts of glue or epoxy as the mounting stiffness may be reduced and compromise
11. ange For these reasons it is recommended that a recalibration cycle be established for each accelerometer This schedule is unique and is based on a variety of factors such as extent of use environmental conditions accuracy requirements trend information obtained from previous calibration records contractual regulations frequency of cross checking against other equipment manufacturer recommendation and any risk associated with incorrect readings International standards such as ISO 10012 1 provide insight and suggest methods for determining recalibration intervals for most measuring equipment With the above information in mind and under normal circumstances PCB conservatively suggests a 12 to 24 month recalibration cycle for most piezoresistive accelerometers NOTE t is good measurement practice to verify the performance of each accelerometer with a calibration device before and after each measurement 8 1 RECALIBRATION SERVICE PCB offers recalibration services for our piezoresistive accelerometers as well as units produced by other manufacturers Our internal metrology laboratory is certified to ISO 9001 accredited by A2LA to ANSI IEC 17025 and ANSI NCSL 7540 1 complies with ISO 10012 1 and former MIL STD 45662A and uses equipment directly traceable to NIST Our investment in equipment traceability and conformance to industry standards ensures accurate calibration against relevant specifications in
12. e Warranty All equipment and repair services provided by PCB Piezotronics Inc are covered by a limited warranty against defective material and workmanship for a period of one year from date of original purchase Contact PCB for a complete statement of our warranty Expendable items such as batteries and mounting hardware are not covered warranty Mechanical damage to equipment due to improper use is not covered by warranty Electronic circuitry failure caused by the introduction of unregulated or improper excitation power electrostatic discharge is not covered by warranty Contact Information International customers should direct all inquiries to their local distributor or sales office A complete list of distributors and offices can be found at www pcb com Customers within the United States may contact their local sales representative or a factory customer service representative A complete list of sales representatives can be found at www pcb com Toll free telephone numbers for a factory customer service representative in the division responsible for this product can be found on the title page at the front of this manual Our ship to address and general contact numbers are PCB Piezotronics Inc 3425 Walden Ave Depew NY 14043 USA Toll free 800 828 8840 24 hour SensorLine 716 684 0001 Website www pcb com E mail info pcb com General OPERATING GUIDE for use with High Sensit
13. e standard is imperative Sensors with mounting holes are attached directly to the reference standard with a stud tightened to the recommended mounting torque A shouldered mounting stud is typically used to prevent the stud from bottoming out in the hole Both mounting surfaces are precision machined and lapped to provide a smooth flat interface according to the manufacturer s specification A thin layer of silicone grease is placed between the mating surfaces to fill any imperfections and increase the mounting stiffness The cables are stress relieved by first routing them to the shaker head then to a nearby stationary location This reduces cable motion and helps to prevent extraneous motion or stresses from being imparted into the system A typical set up is shown in Figure 12 Mounting surfaces are smooth and flat with a small portion of grease on the interfaces Sensors are mounted with a torque wrench to spec ified requirements Test Sensor Stress Relief v Cable P Reference Thread Locker Standard on Connector Tape or Cable Tie V By T vf Fixed Surface 4 Exciter Axis of Motion Figure 12 Typical Calibration Set Up Adhesively mounted sensors use similar practices However in this case a small portion of quick bonding gel or similar temporary adhesive is used to attach the test sensor to a reference st
14. erometers Method 1 if at all possible Method 2 should be avoided as a general rule to avoid damage to the accelerometer during removal STEP 1 Prepare a smooth flat mounting surface A minimum surface finish of 32 pin 0 0008 mm generally works best STEP 2 Place a small portion of adhesive on the underside of the sensor Firmly press down on the top of the assembly to displace any adhesive Be aware that excessive amounts of adhesive can make sensor removal difficult Also adhesive that may invade the mounting holes in the sensor will compromise future ability to screw mount the unit ADHESIVE JOINT 4 2 1 ADHESIVE MOUNT REMOVAL other than wax Caution It is usually difficult or near impossible to remove a direct adhesive mounted high sensitivity DC transducer without damaging it That is adhesive mounted with cyanoacrylate or epoxy without use of an intermediary mounting base However adhesive mounting is often used for temporary installation or when the test object surface cannot be adequately prepared for screw mounting NOTE A chemical debonder should always be used to avoid sensor damage Care should be exercised to avoid excessive force being applied to case body during removal To avoid damaging the accelerometer a de bonding agent must be applied to the adhesive prior to sensor removal With so many adhesives in use everything from super glues dental cement epoxies etc there is no universal de bondin
15. evices and compare the data as shown in Figure 10 Test set ups may be automated and vary depending on the type and number of accelerometers being calibrated Reference Signal Conditioners 7 Standard 1 T ra Sensor e S Readouts gt J 1010 00 oN O eeee 00 Exciter Function Generator Figure 10 Typical Back to Back Calibration System Because the acceleration is the same on both sensors the ratio of their outputs must also be the ratio of their sensitivities With the sensitivity of the reference standard Sg known the exact sensitivity of the test sensor Sr is easily calculated by using the following equation 5 Sa By varying the frequency of the vibration the sensor may be calibrated over its entire operating frequency range The typical response of an unfiltered accelerometer is shown in Figure 11 Magnitude A dB PA A Phase N S Figure 11 Typical Test Accelerometer Response 8 3 PCB CALIBRATION PROCEDURE Numerous precautions are taken at PCB to insure accurate and repeatable results This section provides a brief overview of the primary areas of concern Since the Back to Back Calibration technique relies on each sensor experiencing an identical acceleration level proper mounting of the test sensor to the referenc
16. g agent available The de bonder for the Loctite 454 adhesive that PCB offers is Acetone If you are using anything other than Loctite 454 you will have to check with the individual manufacturers for their de bonding recommendations The de bonding agent must be allowed to penetrate the surface in order to properly react with the adhesive so it is advisable to wait a few minutes before removing the sensor After the de bonding agent has softened the adhesive use a gentle shearing or twisting motion by hand only to remove the sensor from the test structure 5 0 CABLING 5 1 Units with integral connectors Care and attention to cable installation and cable condition is essential as the reliability and accuracy of any measurement system is no better than that of its weakest link Due to the nature of vibration and shock measurements all sensor cables will ultimately fatigue and fail Good installation practice will extend the life of a cable however it is highly recommended to keep spare cables on hand to enable continuation of the test in the event of a cable failure STEP 1 Ascertain that you have the correct cable type Note Most high sensitivity DC accelerometers have integral cable connections therefore the cable leads at the opposite end from the accelerometer are the main focus and will apply to the specific connector plugs associated with follow on electronics signal conditioning equipment One cable type cannot satisfy
17. herent noise floor of accelerometer High Sensitivity DC Accelerometers typically have Low impedance output signal Steady state acceleration measurement capability Stable operation over temperature Low cross axis sensitivity PCB s High Sensitivity DC accelerometers are designed utilizing a MEMS Micro Electro Mechanical Systems silicon sensor approach The micro machining design process provides sensor design flexibility reliability amp stability over time Compared to standard strain gages silicon sensor accelerometers have a much higher gage factor The sensor element of the 3741 series features a proof mass ringframe and an attachment system between the two These features are micromachined from the same single crystal silicon wafer The sensor is connected as a bridge element in the circuit The electrical characteristics of one portion of the bridge increases while the other decreases when exposed to acceleration The sensor element itself is kept small through the use of cutting edge processes such as DRIE Deep Reactive Ion Etching Ruggedness is enhanced through the use of mechanical stops on the two outer wafers to restrict the travel of the proofmass Gas damping is used to mitigate high frequency inputs An on board voltage regulator allows an excitation range of 6 to 30 Vdc with less than or equal to 5 mA current draw The positive output signal line increases with acceleration while the negative line decreases
18. high frequency performance It may also damage the sensor during removal Excessive Epoxy Figure 14 Incorrect Adhesive Mounting Triaxial accelerometers should always be mounted directly to the reference standard Use of adaptors may be required for calibration of three individual accelerometers oriented in a triaxial arrangement The vibration at the test sensor s sensing element may differ from the vibration at the reference standard due to a cantilever effect seen in Figure 15 Figure 15 Mounting Triaxial Sensors Incorrect Understand Back to Back Calibration limitations Do not expect the uncertainty of calibration to be any better than 2 In fact the uncertainty may be as high as 3 or 4 for frequencies 10 Hz or gt 2 kHz Since large sensors may affect high frequency accuracy verify that the test sensor does not mass load the reference standard Validate your calibration system with another accelerometer prior to each calibration session Check with the manufacturer for exact system specifications 8 5 CONCLUSIONS Without an adequate understanding of dynamics determining what when and how to test a sensor is a difficult task Therefore each user must weigh the cost time and risk associated with self calibration versus utilizing the services of an accredited laboratory 9 0 SERVICE See the supp
19. ices or special testing contact your local Piezotronics distributor sales representative or factory customer service representative Returning Equipment Following these procedures will insure that your returned materials are handled in the most expedient manner Before returning any equipment to PCB Piezotronics contact your local distributor sales representative or factory customer service representative to obtain a Return Materials Authorization RMA Number This RMA number should be clearly marked on the outside of all package s and on the packing list s accompanying the shipment A detailed account of the nature of the problem s being experienced with the equipment should also be included inside the package s containing any returned materials A Purchase Order included with the returned materials will expedite the turn around of serviced equipment It is recommended to include authorization on the Purchase Order for PCB to proceed with any repairs as long as they do not exceed 50 of the replacement cost of the returned item s PCB will provide a price quotation or replacement recommendation for any item whose repair costs would exceed 50 of replacement cost or any item that is not economically feasible to repair For routine calibration services the Purchase Order should include authorization to proceed and return at current pricing which can be obtained from a factory customer service representativ
20. ion machined mounting surface with a minimum finish of 32 pin 0 0008 mm is recommended If and only if it is not possible to properly prepare the test structure mounting surface consider adhesive mounting as a possible alternative Inspect the area checking that there are no burrs or other foreign particles interfering with the contact surface STEP 2 Wipe clean the mounting surface and spread on a light film of grease oil or similar coupling fluid prior to installation Figure 4 Mounting Surface Lubrication Adding a coupling fluid improves vibration transmissibility by filling small voids in the mounting surface and increasing the mounting stiffness For semi permanent mounting substitute epoxy or another type of adhesive STEP 3 Attach supplied washers insert screws through hole in accelerometer case and torque to specified value per Installation Drawing NOTE is important to use a torque wrench during this step Under torquing the sensor may not adequately couple the device over torquing may result in screw failure 4 2 ADHESIVE MOUNT Adhesives like hot glue and wax perform well for temporary installations whereas two part epoxies and quick bonding gels super glue provide a more permanent installation PCB recommends mounting DC accelerometers via an adhesive mounting base The base acts as a sacrificial part allowing safe removal of accelerometer after test is completed NOTE
21. ivity DC ACCELEROMETERS SPECIFICATION SHEET INSTALLATION DRAWING AND CALIBRATION INFORMATION ENCLOSED PCB ASSUMES NO RESPONSIBILITY FOR DAMAGE CAUSED TO THIS PRODUCT AS A RESULT OF PROCEDURES THAT ARE INCONSISTENT WITH THIS OPERATING GUIDE 1 0 INTRODUCTION Congratulations on the purchase of a quality DC acceleration sensor PCB s high sensitivity DC accelerometers provide optimal performance characteristics in a high quality package In order to ensure the highest level of performance for this product it is imperative that you properly familiarize yourself with the correct mounting and installation techniques before attempting to operate this device If after reading this manual you have any additional questions concerning this sensor or its application feel free to call a factory Application Engineer at 716 684 0001 or your nearest PCB sales representative 2 0 HIGH SENSITIVITY DC ACCELEROMETERS High sensitivity DC accelerometers are devices which require stable power Unlike standard non amplified piezoresistive accelerometer designs this stable power is provided by an internal voltage regulator Therefore PCB s high sensitivity DC accelerometers may be supplied with a positive unregulated DC supply voltage provided it falls within the specified range of the particular model number The change in the silicon strain sensing element is approximately proportional to the applied acceleration The sensor element is electrically
22. lement sheet contained in this manual for information on our warranty service repair and return policies and instructions When unexpected measurement problems arise call our 24 hour SensorLine to discuss your immediate dynamic instrumentation needs with a factory representative Dial 716 684 0001 PCB PIEZOTRONICS VIBRATION DIVISION 3425 Walden Avenue Depew NY 14043 2495 USA Vibration Division toll free 888 684 0013 24 hour SensorLine 716 684 0001 FAX 716 685 3886 E mail vibration pcb com Website www pcb com A PCB GROUP COMPANY ISO 9001 CERTIFIED A2LA ACCREDITED to ISO 17025 2002 PCB Group Inc In the interest of constant product improvement specifications are subject to change without notice PCB and ICP are registered trademarks of PCB Group Inc SensorLine is a service mark of PCB Group Inc All other trademarks are properties of their respective owners Manual Number 32258 ECN Number 36609 VIB High Sensitivity DC MANUAL Printed in U S A Manual Revision A Model Number Revision B DC RESPONSE ACCELEROMETER OPTIONAL VERSIONS Optional versions have identical specifications and accessories as listed for the standard model except where noted below More than one option may be used Performance Sensitivity 5 Measurement Range Frequency Range 5 Frequency Range x 10 Resonant Frequency Phase Response 100 Hz Broadband Resolution 0 5 to 100 Hz Non Linearity Transverse Sensitivi
23. ne powered units provide the capability for continuous monitoring Note High sensitivity DC Accelerometers feature on board differential amplification 7 0 OPERATING NOTE Always operate the accelerometer within the limitations listed on the enclosed Specification Sheet Operating the device outside these parameters can cause temporary or permanent damage to the sensor 8 0 ACCELEROMETER CALIBRATION Accelerometer calibration provides with a definable degree of accuracy the necessary link between the physical quantity being measured and the electrical signal generated by the sensor In addition other useful information concerning operational limits physical parameters electrical characteristics or environmental influences may also be determined Without this link analyzing data becomes a nearly impossible task Fortunately most sensor manufacturers provide a calibration record that documents the exact characteristics of each sensor The type and amount of data varies depending on the manufacturer sensor type contractual regulations and other special requirements Under normal conditions high sensitivity DC sensors are extremely stable and their calibrated performance characteristics do not change over time However the sensor may be temporarily or permanently affected by harsh environments influences or other unusual conditions that may cause the sensor to experience dynamic phenomena outside of its specified operating r
24. on Fig 6 It should be regulated and stable to within 0 196 or better Noise and ripple should be equally low since noise will be transmitted directly to the signal leads of the bridge However an unregulated DC supply may be used due to the high sensitivity DC accelerometer having its own on board voltage regulator The signal should be connected to a good instrumentation grade differential input amplifier The amplifier should have high input impedance gt 1 MQ and good common mode rejection The amplifier should also have adequate bandwidth to accommodate the measurement application NOTE Damage to the sensor elements resulting from the application of incorrect power or the use of an unapproved power source is NOT covered by warranty Regulated Instrument Power Supply VE Transducer dii aec yo Cable Shield FR LI ST Instrumentation Amplifier Figure 6 Typical DC Accelerometer Signal Conditioning System Schematic Model 3741 Transducer Fe Housing Shiel od a F i Voltage i Input Power Regulalor H 6 to 30 VDC 1 Differential ri Oulput o Yellow Do HAVC MEMS 8 Signal Acceleration Sensor Element White Signal Figure 7 Typical High Sensitivity DC Accelerometer System Schematic In general battery powered devices offer versatility for portable low noise measurements whereas li
25. paired in the field simply by re soldering the stripped leads to the exposed pins on the sensor Check the Installation Drawing to determine pin functions In many cases it is also helpful to protect the solder joint with heat shrink tubing or epoxy It should be noted that cable breaks too close to the accelerometer case may not be repairable due to insufficient cable material for repair NOTE f you do not have the experience or resources to attach pigtail leads consult PCB to discuss factory attachment Damage to internal electronics may be caused by excessive heat during soldering and such failure is not covered by warranty STEP 3 Route the cable to the signal conditioner making certain to relieve stress on the sensor cable connection Also minimize cable motion by securing it with tape clamps or ties at regular intervals Common sense should be used to avoid physical damage and minimize electrical noise For instance avoid routing cables near high voltage wires Do not route cables along floors or walkways where they may be stepped on or become contaminated To avoid ground loops shielded cables should have the shield grounded at one end only typically at the signal conditioner STEP 4 Finally connect the remaining cable end to the signal conditioner 6 0 Signal Conditioning For optimum performance and flexibility high sensitivity DC accelerometers benefit from a good stable low noise dc power supply for excitati
26. proportionally The output lines have a common mode voltage of 2 5 Vdc above circuit ground Consult the individual accelerometer data sheet on how to order the particular model most appropriate for your application Adhesive mounting plates triaxial mounting blocks are available If you have any questions or concerns regarding optional configurations consult the Vibration Division s product catalog or contact a PCB factory representative 4 0 INSTALLATION OVERVIEW PCB s high sensitivity DC accelerometers are supplied with a silicone jacketed shielded multi conductor integral cable assembly With each conductor being 30 AWG Teflon coated The supplied cable length for a standard DC accelerometer is 10 ft or 120 in 3 m Custom cable length requirements should be specified at time of ordering When applications involve very long cable runs the user is advised to take into consideration the added resistance of the cable wires and additional capacitance values as this may affect the voltage available at the accelerometers input voltage regulator Ensure the recommended torque is used for the supplied 4 40 mounting cap screws The 3741 is packaged in a hard anodized aluminum case 0 3 in high with a footprint of 0 85 in by 1 0 in The high sensitivity DC accelerometer output signal is considered a differential signal which should be routed to a differential amplifier or bridge conditioner see Fig 6 The bridge condi
27. tioner should supply a regulated dc supply and have proper amplification features Although a simple unregulated DC voltage supply is an acceptable condition for operation bridge conditioning equipment typically has ZMO adjustment capability and standard connector accessories included which provide a plug amp play environment Excitation input and Voltage output wiring conform to the following color coding practice Excitation input red excitation input black signal output yellow signal output white Multi pin connectors For accelerometer versions with detachable cabling make connection by inserting the sensor s mating pins onto the cable connector s mating sockets Then thread the connector into place by turning the cable connector s outer shell onto the accelerometer s electrical connector 4 1 SCREW MOUNT This mounting technique requires smooth flat contact surfaces for proper operation and is recommended for permanent and or secure installations Screw mounting is recommended when testing at high frequencies STEP 1 First prepare a smooth flat mounting surface then drill and tap mounting holes for mounting as shown in Figure 3 and in accordance with the enclosed Installation Drawing SCREW ATTACHMENT TORQUE TO PROPER MODEL 3741 DC VALUE ACCELEROMETER MOUNTING STRUCTURE FLAT WITH GOOD FINISH Figure 3 Mounting Surface Preparation A precis
28. ty Environmental Overload Limit Shock Temperature Range Operating Temperature Range Storage Temperature Coefficient of Sensitivity Zero g Offset Temperature Coefficient Base Strain Sensitivity Electrical Excitation Voltage Current Consumption Output Impedance Offset Voltage 0 g Common Mode Voltage 0 1 VDC Spectral Noise 1 to 100 Hz Electrical Isolation Case Physical Housing Material Sealing Size Height x Length x Width Weight without cable Electrical Connector Electrical Connection Position Cable Termination Cable Type Cable Length Mounting 8 ENGLISH 66 7 mV g 30g pk 0 to 1000 Hz 0 to 1500 Hz gt 4 kHz lt 10 3 5 mg rms lt 1 FS lt 3 3000 g pk 65 to 250 F 65 to 250 F 3 0 96 2 0 FSO 0002 g pe 6 to 30 VDC lt 6mA lt 100 Ohm 40 mVDC 2 5 VDC 390 yg VHz gt 108 Ohm Anodized Aluminum Epoxy 0 30 in x 1 00 in x 85 in 0 35 oz Integral Cable Side Pigtail Ends 010 4 cond Shielded 10 ft Through Holes 2 All specifications are at room temperature unless otherwise specified In the interest of constant product improvement we reserve the right to change specifications without notice SI 6 80 mV m s 294 2 m s pk 0 to 1000 Hz 0 to 1500 Hz gt 4 kHz 10 0 034 m s rms 196 FS lt 3 29 420 m s pk 54 0 to 121 C 54 0 to 121 C 3 0 2 0 FSO 002 m s ue 6 to 30 VDC lt 6 mA lt 100 Ohm 40 mVDC 2 5 VDC 382
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