LVDT-8 Manual - ACCES I/O Products, Inc.
Contents
1. FED 9 59 219 cal 20 9 59 2 19 9 2 19 991 970 tco FEO c 9 59 2 19 FEO 219 Figure 3 1 Option Selection Map Manual MLVDT8 E1b Page 3 3 LVDT 8 Manual TB2 thru TB9 Screw Terminal Connections 1 amp 2 Sensor Excitation 3 amp 4 Sensor Output 5 Shield Common or Ground Note not connect terminals 4 amp 5 together The post amplifier gain is selected by jumper installation at the jumper block labeled G ALL That block is located immediately adjacent to connector J2 and above the output channel select jumper block If a jumper is installed the gain is 2 If a jumper is not installed the gain is 3 An approximation of the DC output of the LVDT 8 card is as follows 0 9 x LVDT sensor input in RMS units x Preamplifier gain x Postamplifier gain When deciding what gains to use at the preamplifier and the post amplifier it is important to remember that the ou2. Figure 3 1 Option Selection Map esc eei ed E ERE RR ERES RENS 3 3 List of Tables Table 6 1 Connector Pin Assignments 0 0 6 1 Page vi Chapter 1 Introduction Linear Variable Differential Transformers LVDTs are the most commonly used passive type displacement transducers They operate under the principle of a mutual inductance change due to movement of a magnetic core This movement produces an electrical output proportional to the displacement of the core An AC 5kHz 3 2V rms excitation voltage is applied to the primary winding see the specification section for other frequency options Two identical secondary windings symmetrically spaced from the primary are connected in a series opposing circuit Motion of the magnetic core varies the mutual inductance of each secondary to the primary which in turn determines the voltages induced from the primary to each of the secondaries If the core is centered between the secondary windings the voltage induced in the secondaries 15 identical and 180 degrees out of phase so there is no net output This is the NULL point If the core is moved off center the mutual inductance of the primary with one secondary is greater than with the other and an AC differential voltage appears across the secondaries in series For displacements within the operating range of the transducer used this voltage is a linear analog of the displacement Each LVDT 8 card
3. Actual frequency may be slightly different Available Gains Each channel has a gain from 1 to 8 selected by jumpers and adjustment potentiometers A post amplifier provides a gain of 2 or 3 applied to all channels on a card Control Inputs Three binary digital inputs for channel selection Logic levels compatible with LSTTL logic Power Required 12 VDC at 230 mA 12 VDC at 230 mA Output Analog Voltage 5 VDC Environmental Operating Temperature Range 0 C to 65 C Storage Temperature Range 40 C to 100 C Humidity 0 to 9096 non condensing Size LVDT 8 module 8 0 long 203 mm X 4 74 wide 120 mm X 0 75 high 19 mm Fits inside of T BOX enclosure included Size T BOX 8 5 long 216 mm X 5 25 wide 133 mm X 2 0 high 51 mm Manual MLVDT8 E1b Page 1 3 LVDT 8 Manual PREAMP LVDT 1 EET 1 LVDT 3 VO CIRCUITS LVDT 4 VO CIRCUITS BUF LVDT 5 VO CIRCUITS D LJ Gain All LVDT 6 VO CIRCUITS INDT 7 VO CIRCUITS LVDT 8 VO CIRCUITS xaz VOLTAGE REGULATOR Figure 1 1 LVDT 8 Block Diagram Page 1 4 A2 A1 FROM A D CONVERTER AO OVO OV1 J Ove O Ov3 Oo OUTPUTS TO oO A D CONVERTER OV5 OV6 Manual MLVDT8 E1b Chapter 2 Installation The software provided with this card is contained on either one CD or multiple diskettes and must be installed onto your hard disk prior to use To do this perform the following
4. for use with the LVDT 8 EASY ACCESS was designed to work seamlessly with the AD12 8 A D converter and because the software is completely menu driven you can set up and run data acquisition without doing any programming The EASY ACCESS manual is a separate manual included within the LVDT 8 manual binder EASY ACCESS provides an update rate of approximately 100 channels per second If more elaborate or faster data acquisition is required then you may use the drivers provided with the AD12 8 card and write your own dedicated program For programming analog to digital converter cards other than the AD12 8 use the following sensor selection table Sensors connected to the LVDT 8 module are multiplexed to a single output channel via the Output multiplexer IC type HI 508 Digital inputs AO Al and A2 are used to select individual sensors These correspond to lines OPO and OP2 respectively at the AD12 8 card A2 PIN9 AI PINS 0 7 The input voltage range of the AD12 8 A D card should be set to 5VDC Review the software examples provided on the CD or the Calibration chapter for more information Manual MLVDT8 E1b Page 4 1 LVDT 8 Manual Page 4 2 Manual MLVDT8 E1b Chapter 5 Calibration Refer to the Block Diagram and Option Selection Map presented earlier in this manual for guidance as you perform the calibration procedure A simplified calibration procedure is part of the setup program provided on CD Equi
5. steps as appropriate for your software format and operating system Substitute the appropriate drive letter for your CD ROM or disk drive where you see d or a respectively in the examples below CD Installation DOS WIN3 x 1 Place the CD into your CD ROM drive 2 Type d K to change the active drive to the CD ROM drive 3 Type installK to run the install program 4 Follow the on screen prompts to install the software for this card WIN95 98 NT a Place the CD into your CD ROM drive b The CD should automatically run the install program after 30 seconds If the install program does not run click START RUN and type d install click OK or press Follow the on screen prompts to install the software for this card 3 5 Inch Diskette Installation As with any software package you should make backup copies for everyday use and store your original master diskettes in a safe location The easiest way to make a backup copy is to use the DOS DISKCOPY utility In a single drive system the command is diskcopy a a K You will need to swap disks as requested by the system In a two disk system the command is diskcopy a b K This will copy the contents of the master disk in drive A to the backup disk in drive B Manual MLVDT8 E1b Page 2 1 LVDT 8 Manual To copy the files on the master diskette to your hard disk perform the following steps a Place the master diskette into a floppy drive b Change the active drive to t
6. supplies power excitation and signal conditioning for up to eight independent LVDT transducers Up to eight LVDT 8 cards may be connected to one AD12 8 Analog Input Card thereby supporting up to 64 LVDTs Alleight LVDT Signal Processor chips have oscillator capability To assure that all eight sensors will be excited by the same frequency a synchronizing signal is supplied by the oscillator associated with LVDT 1 to the seven other signal processor chips If more than one LVDT 8 is to be used then you can assure that ALL sensors regardless which card they are connected to will be excited by the same source You do this by placement of Master Slave jumpers as described in the Option Selection section of this manual The 5 KHz signals from the secondary windings are amplified and then converted to DC by synchronous demodulators and low pass active filters prior to application to the output multiplexer These DC signals are the measure of LVDT core movements at each transducer Offset gain and phase correction adjustments are provided The phase adjustment eliminates minor phase differences between the primary and secondary windings of each LVDT transducer Manual MLVDT8 E1b Page 1 1 LVDT 8 Manual All DC outputs are connected to an 8 1 multiplexer Each DC output is selected by the multiplexer under control of three address lines from the A D card in the host computer The output is connected via a post amplifier and one of the jumpers OVO
7. 0 Table 6 1 Connector Pin Assignments Manual MLVDT8 E1b Page 6 1 LVDT 8 Manual Page 6 2 Manual MLVDT8 E1b Customer Comments If you experience any problems with this manual or just want to give us some feedback please email us at manuals accesioproducts com Please detail any errors you find and include your mailing address so that we can send you any manual updates ya ACCES I O PRODUCTS INC 10623 Roselle Street San Diego CA 92121 Tel 619 550 9559 FAX 619 550 7322 www accesioproducts com
8. ACCES PRODUCTS INC 10623 Roselle Street San Diego CA 92121 TEL 858 550 9559 FAX 858 550 7322 MODEL LVDT 8 USER MANUAL FILE MLVDT8 E1b Notice The information in this document is provided for reference only ACCES does not assume any liability arising out of the application or use of the information or products described herein This document may contain or reference information and products protected by copyrights or patents and does not convey any license under the patent rights of ACCES nor the rights of others IBM PC PC XT and PC AT are registered trademarks of the International Business Machines Corporation Printed in USA Copyright 1995 by ACCES I O Products Inc 10623 Roselle Street San Diego CA 92121 rights reserved Pageiii Warranty Prior to shipment ACCES equipment is thoroughly inspected and tested to applicable specifications However should equipment failure occur ACCES assures its customers that prompt service and support will be available equipment originally manufactured by ACCES which is found to be defective will be repaired or replaced subject to the following considerations Terms and Conditions If a unit is suspected of failure contact ACCES Customer Service department Be prepared to give the unit model number serial number and a description of the failure symptom s We may suggest some simple tests to confirm the failure We will assign a Return Material Authorization
9. RMA number which must appear on the outer label of the return package All units components should be properly packed for handling and returned with freight prepaid to the ACCES designated Service Center and will be returned to the customer s user s site freight prepaid and invoiced Coverage First Three Years Returned unit part will be repaired and or replaced at ACCES option with no charge for labor or parts not excluded by warranty Warranty commences with equipment shipment Following Years Throughout your equipment s lifetime ACCES stands ready to provide on site or in plant service at reasonable rates similar to those of other manufacturers in the industry Equipment Not Manufactured by ACCES Equipment provided but not manufactured by ACCES 15 warranted and will be repaired according to the terms and conditions of the respective equipment manufacturer s warranty General Under this Warranty liability of ACCES is limited to replacing repairing or issuing credit at ACCES discretion for any products which are proved to be defective during the warranty period In no case is ACCES liable for consequential or special damage arriving from use or misuse of our product The customer is responsible for all charges caused by modifications or additions to ACCES equipment not approved in writing by ACCES or if in ACCES opinion the equipment has been subjected to abnormal use Abnormal use for purposes of this warranty is defined as any us
10. VDT 8s in a system then one must be designated the Master and the others may be designated Slaves A Master card is designated by installing jumpers in the two positions labeled MSTR that are located near ribbon cable connectors J1 and J2 A Slave card is designated by installing jumpers in the two positions labeled SLV that are located at those same locations Interconnection is via a ribbon cable from the J2 connector on the master card or through other slave cards Manual MLVDT8 E1b Page 3 1 LVDT 8 Manual In a system that contains only one LVDT 8 that LVDT 8 must be configured as a master The jumper in the other SLV jumper block must be installed to internally slave the other channels to channel one In a multiple card system there are several options A multiple card system may contain a Master card and as many Slave cards as the analog input card can support This assures that all LVDT sensors are excited from the same frequency A multiple card system may contain all Masters This means that all sensors connected to a given LVDT 8 will be excited by the same source but each card will provide excitation according to the oscillator on that particular card For both situations the chain of LVDT 8 cards should start with a connection of the Master LVDT 8 card to the AD12 8 side via 37 pin connector J1 and with connections to Slave cards from J2 of the Master LVDT 8 to on the Slave card until it ends with no connection to co
11. anual MLVDT8 E1b Chapter 3 Option Selection LVDT 8 options are selected by placement of jumpers on the card In the text that follows jumper identification is given in capital letters and is identical to what is silk screened on the board Refer to the Block Diagram on the preceding page and the Option Selection Map at the end of this section The setup program provided on CD illustrates the location of jumpers and adjustment potentiometers Output Channel Jumper positions labeled OVO through OV7 are used to select the LVDT 8 output to an AD12 8 or compatible analog input channel The jumper block is immediately adjacent to the ribbon cable I O connectors J1 and J2 External 12VDC and 12VDC Power Two jumper blocks located between the ribbon cable connectors and terminal block TB1 are used to connect 12V power to the LVDT 8 If computer power carried by the ribbon cable is used the jumpers should be placed in the PS positions If an external power supply is used then these jumpers should be placed in the EX positions and the power supply connected to the adjacent screw terminals on TBI Sensor Excitation While all of the LVDT Signal processor chips contain oscillator capability the output of U7 is used as the master oscillator and a synchronizing signal from U7 is supplied to the other signal processor chips In this way you are assured that all eight sensors will be excited by the same source If there are to be more than one L
12. determine an available address to give the card Once the address has been determined run the setup program provided with the hardware to see instructions on setting the address switch and various option selections Poly exe A generic utility to convert a table of data into an nth order polynomial Useful for calculating linearization polynomial coefficients for thermocouples and other non linear sensors Risc bat A batch file demonstrating the command line parameters of RISCTerm exe RISCTerm exe A dumb terminal type communication program designed for RS422 485 operation Used primarily with Remote Data Acquisition Pods and our RS422 485 serial communication product line Can be used to say hello to an installed modem RISCTerm stands for Really Incredibly Simple Communications TERMinal Installing the Hardware Prior to installing LVDT 8 refer to the Option Selection section of this manual and place jumpers as required for the mode of operation that you wish The LVDT 8 is installed external to the host computer and a steel enclosure model T BOX is provided 37 conductor ribbon cable is available to provide interconnection to AD12 8 multiplexed analog to digital converter A D installed in an I O slot of the computer If pin connections are correct the LVDT 8 may also be used with other multiplexed A D converters As many as eight LVDT 8 modules may be cascaded to accommodate up to 64 LVDTs In this case the modules are cha
13. e to which the equipment is exposed other than that use specified or intended as evidenced by purchase or sales representation Other than the above no other warranty expressed or implied shall apply to any and all such equipment furnished or sold by ACCES Page iv Table of Contents NO CE qc M PT iii Warranty a x ed ble ee bed 16 e 805 ew nds due ee iv Chapter 1 Introduction 509 vie ee neg elit bete ew tee wel owe ele in 1 1 SPECHICAUONS re bM LO MR LEE 1 3 Chapter 2 Installation ooooooooooccrar eee 2 1 CD Installatirt heh ea dad 2 1 3 5 Inch Diskette Installation Soda eee Rd ie Re o e 2 1 Directories Created on the Hard Disk 2 2 Installing the Hardware sa Art tie ct cere Le Le cA M ef 2 4 Chapter 3 Option Selection Ra aw 3 1 OUIDUP Ghantele s Ae RA cM oM Lt aia o E a 3 1 External 12VDC and 12VDC Power 3 1 SENSOMEXCHANON wax adobe oa eee Ra Ql qr EU A EQ Re UU aes 3 1 Selecting Amplifier Gain aan a ea Brot ehe antt tese de efte A teda 3 2 Chapter 4 Software nr a rs a ic d e eas 4 1 Chapter 5 Calibration ERE Y EE EC 5 1 Chapter 6 Connector Pin Assignments 6 1 Page v List of Figures Figure 1 1 LVDT 8 Block Diagram an mre ea are u Secr 1 4
14. he drive that has the diskette installed For example if the diskette is in drive A type a K e Type installK and follow the on screen prompts Directories Created on the Hard Disk The installation process will create several directories on your hard disk If you accept the installation defaults the following structure will exist CARDNAME Root or base directory containing the SETUP EXE setup program used to help you configure jumpers and calibrate the card DOS PSAMPLES A subdirectory of CARDNAME that contains Pascal samples DOS CSAMPLES A subdirectory of CARDNAME that contains C samples Win32 language Subdirectories containing samples for Win95 98 and NT WinRisc exe A Windows dumb terminal type communication program designed for RS422 485 operation Used primarily with Remote Data Acquisition Pods and our RS422 485 serial communication product line Can be used to say hello to an installed modem ACCES32 This directory contains the Windows 95 98 NT driver used to provide access to the hardware registers when writing 32 bit Windows software Several samples are provided in a variety of languages to demonstrate how to use this driver The DLL provides four functions InPortB OutPortB InPort and OutPort to access the hardware This directory also contains the device driver for Windows NT ACCESNT SYS This device driver provides register level hardware access in Windows NT Two methods of using the driver are availab
15. ht re adjustment 9 10 11 12 Page 5 2 If not satisfied with calibration results repeat all steps beginning with step 5 If other LVDT sensors of the same type are to be used and if it was necessary to remove the phase shift capacitors remove the corresponding capacitors from all channels that will use these sensors Capacitors C30 C38 C46 C54 C62 C70 C78 and C86 are the input phase shift capacitors for channels 1 through 8 respectively Do not remove any capacitors from inputs that will use another type or model LVDT sensor Connect and calibrate all other LVDT sensors one at a time using the zero adjust phase shift and gain potentiometers corresponding to the particular channel Once all LVDT sensors are installed and calibrated recheck each sensor to see that its calibration i e position input versus voltage output is still correct Manual MLVDT8 E1b Chapter 6 Connector Pin Assignments Two parallel 37 pin D Sub type connectors are provided on the LVDT 8 module The mating connectors are AMP type 747304 1 or equivalent 12 V POWER UNUSED AAA MASTERSLAVESYNC VS 7 AO LSB FOR CHANNEL SELECT Al A2 paz MSBFORCHANNELSELECT 10 UNUSED 12 UNUSED 14 o A AAA AGND ANALOG GROUND 19 UNUSED 12 V POWER UNUSED N N wN N I 25 0 N oo AAA 29 30 32 33 34 35 OUTPUT TO A D CHANNEL 1 OUTPUT TO A D CHANNEL
16. ined together by 37 conductor ribbon cables and the first module in the chain provides connection to the A D as described above The address of each LVDT 8 is established by selecting an output channel via a jumper installed at locations marked OVO through OV7 Page 2 4 Manual MLVDT8 E1b Signals from the transducers to the LVDT 8 module are connected via eight terminal blocks labeled TB 2 through TB 9 To ensure that there is minimum susceptibility to EMI proper EMI cabling techniques twisted pair wiring and in extreme cases shielded wiring should be used on input wiring Each of the terminal blocks has five terminals 1 2 Primary winding 3 4 Secondary winding 5 Chassis Ground If the optional CT BOX is used then input connections must be made from the circular DIN connectors to these terminal blocks Each LVDT 8 card requires 230 mA of 12VDC and 230 mA of 12VDC If the 12VDC and 12VDC power supplies in your computer cannot provide the current required in your application then it will be necessary to use an external power supply with adequate rating Connect inputs from that supply to terminal block TB1 and change the jumpers adjacent to that terminal block from the PS position to the EX positions Note To minimize possibility of extraneous noise short terminals 3 and 4 on any unused inputs DO NOT ground the inputs or connect them to pin 5 Manual MLVDT8 E1b Page 2 5 LVDT 8 Manual Page 2 6 M
17. le through ACCES32 DLL recommended and through the DeviceIOControl handles provided by ACCESNT SYS slightly faster Page 2 2 Manual MLVDT8 E1b SAMPLES Samples for using ACCES32 DLL are provided in this directory Using this DLL not only makes the hardware programming easier MUCH easier but also one source file can be used for both Windows 95 98 and WindowsNT One executable can run under both operating systems and still have full access to the hardware registers The DLL is used exactly like any other DLL so it is compatible with any language capable of using 32 bit DLLs Consult the manuals provided with your language s compiler for information on using DLLs in your specific environment VBACCES This directory contains sixteen bit DLL drivers for use with VisualBASIC 3 0 and Windows 3 1 only These drivers provide four functions similar to the ACCES32 DLL However this DLL is only compatible with 16 bit executables Migration from 16 bit to 32 bit is simplified because of the similarity between VBACCES and ACCES32 PCI This directory contains PCI bus specific programs and information If you are not using a PCI card this directory will not be installed SOURCE A utility program is provided with source code you can use to determine allocated resources at run time from your own programs in DOS PCIFind exe A utility for DOS and Windows to determine what base addresses and IRQs are allocated to installed PCI cards This program r
18. nnector J2 on the final Slave card Selecting Amplifier Gain The overall gain of each channel of an LVDT 8 card should be carefully selected so that a change in LVDT sensor displacement over the total desired sensor travel results in the maximum output voltage change without exceeding the limits of the LVDT 8 amplifiers or AD12 8 input amplifiers Both are designed for voltage spans from 5 00V to 5 00V Further to make best use of the LVDT 8 card the output of the sensor should be 0 0V RMS at the center of this displacement range The card contains individual preamplifiers associated with each channel plus one post amplifier on the output of the multiplexer Gain of this post amplifier is common to all channels Warning Use caution in selecting amplifier gain Too high of a gain could create distorted readings or cause the final amplifier to oscillate which might appear as noise The individual preamplifier gains can be adjusted from a gain of 1 to a gain of 8 and thus accommodating sensors of different sensitivities or the same type sensors but with different displacement spans Each channel has a four position jumper selection of gain 1 to 2 2 to 4 3 to 6 and 4 to 8 A gain adjust potentiometer RP2 on channel 0 for example then permits tweaking within the selected range Only one jumper should be installed Page 3 2 Manual MLVDT8 E1b
19. pment Required a b A means of moving the LVDT sensor in precision increments across the desired range of movement a micrometer jig An oscilloscope and a 4 Y digit DVM An XT or AT class computer with an AD12 8 installed connection made from the A D card to the LVDT 8 typically our CAB37 18 cable and the LVDTSET setup program The sensor will be connected to an LVDT 8 input in a later step Calibration Procedure 1 Select a preamplifier gain range of 1 2 the channel to be calibrated by placing the jumper at the G1 2 position Set the G ALL jumper to a gain of 2 by installing the jumper at the G ALL position OFFSET ADJUST Short terminals 3 and 4 together at the input terminal board e g TB2 for channel 0 Adjust the Offset Adjust pot e g RP1 for channel 0 until the DVM or computer program monitor displays 0 0000 volts or the mid scale equivalent if other display units are used Remove the input short from terminals 3 and 4 Connect the sensor to the input terminal board TB2 for channel 0 Terminals 1 and 2 are sensor excitation terminals 3 and 4 are sensor output and terminal 5 is used for a shield ground or common Terminals 4 and 5 must not be tied together Remember to short terminals 3 and 4 on all unused channels Adjust the position ofthe LVDT sensor until the computer monitor display reads 0 0000 volts or equivalent The sensor output at input terminals 3 and 4 should show a null or minimum
20. reading on the oscilloscope PHASE SHIFT ADJUST Adjust the position of the LVDT sensor until the monitor reads approximately 4 volts Now observe the phase shift at pin 5 of the signal processing chip U7 for channel 0 using an oscilloscope The pattern should be similar to a rectified sine wave Adjusting the phase shift potentiometer RP3 for channel 0 should correct any displacement between halves of the rectified sine wave pattern Note Reverse the connections to terminals 3 and 4 if the LVDT responds backwards to what you expect e g Decreasing voltage for increasing deflection 6 If it is not possible to completely correct this displacement with the phase shift adjustment potentiometer then it may be necessary to remove the input phase shift capacitor C30 for channel 0 Before removing this capacitor make certain that all the previous steps have been performed successfully ALSO make certain that power is removed from the LVDT 8 card before removing the capacitor Manual MLVDT8 E1b Page 5 1 LVDT 8 Manual Note Capacitor removal should be accomplished by cutting the component leads rather than unsoldering 7 If it was necessary to remove the phase shift capacitor repeat step 5 above If it is now possible to remove all displacement between rectified halves of the sine wave proceed If not the factory should be consulted 6 Adjust the position of the LVDT sensor until the computer monitor display reads approximately 4
21. through OV7 to one of eight output channels Since each LVDT 8 Module requires only one output channel to pass the data from eight transducers to a host computer and eight output channels are available a total of 64 LVDT transducers can be used with a single AD12 8 A D card from ACCES If more LVDT sensors are required multiple AD12 8 cards can be used in a system Alternatively other multiplexed A D cards can be used as long as proper pin connections are maintained and proper LVDT 8 channel selection commands are generated Warning The LVDT 8 uses pin 4 on the 37 pin connector J1 and J2 to send the oscillator sync signal to other LVDT 8 cards Since other cards may use this pin the LVDT 8 cards should be the last in the chain from the AD12 8 and you should not connect non LVDT 8 cards to the J2 connector on LVDT 8 card Page 1 2 Manual MLVDT8 E1b Specifications The LVDT 8 provides power excitation and signal conditioning for eight independent transducers Conditioned DC outputs are multiplexed and coupled to an analog to digital converter card in a host computer As many as eight LVDT 8s may be cascaded to provide interface for up to 64 transducers Transducers Served LVDT RVDT LVRT with primary impedances of 150 Ohms or greater Excitation Frequency 5 KHz all channels synchronized Optionally the frequency may be anywhere in the range of 1 to 10 KHz Also frequency selection can be made individually for each LVDT channel
22. tput of the preamplifier to the demodulator must not exceed 3 75V peak to peak or serious distortion will occur For example consider the following If the LVDT to be used has a sensitivity of 4 volts inch volt of excitation the linear range of the LVDT is 0 025 inches and the excitation provided by the LSI chip on the LVDT 8 card is nominally 3 2 VRMS then the full scale output of the sensor will be 4 x 0 025 x 3 2 x 1 414 0 452 VP P If a gain of eight is selected at the preamplifier the output to the demodulator in the LSI chip will be 3 62 VP P well within the 3 75 V limit However there is a 3 tolerance on the amplitude of the LSI oscillator circuit output Thus the excitation could be as high as 3 4VRMS and the resulting sensor output would be 4x0 025 x 3 4 x 1 414 2 0 481 VP P In this case if a gain of eight is selected at the preamplifier the output to the demodulator will be 3 85V and distortion will occur In this case the answer is to reduce the gain at the preamplifier Gain at the post amplifier which amplifies outputs on all eight channels should then be selected so that the full scale output falls within the 5 VDC range of the A D converter card Typically a gain of two will be your choice Page 3 4 Manual MLVDT8 E1b Chapter 4 Software Two software programs are provided with the LVDT 8 module the Setup Calibration program and EASY ACCESS a menu driven data acquisition package specifically designed
23. uns two versions depending on the operating system Windows 95 98 NT displays a GUI interface and modifies the registry When run from DOS or Windows3 x a text interface is used For information about the format of the registry key consult the card specific samples provided with the hardware In Windows NT NTioPCI SYS runs each time the computer 1s booted thereby refreshing the registry as PCI hardware is added or removed In Windows 95 98 NT PCIFind EXE places itself in the boot sequence of the OS to refresh the registry on each power up This program also provides some COM configuration when used with PCI COM ports Specifically it will configure compatible COM cards for IRQ sharing and multiple port issues WIN32IRQ This directory provides a generic interface for IRQ handling in Windows 95 98 NT Source code is provided for the driver greatly simplifying the creation of custom drivers for specific needs Samples are provided to demonstrate the use of the generic driver Note that the use of IRQs in near real time data acquisition programs requires multi threaded application programming techniques and must be considered an intermediate to advanced programming topic Delphi C Builder and Visual C samples are provided Manual MLVDT8 E1b Page 2 3 LVDT 8 Manual Findbase exe DOS utility to determine an available base address for ISA bus non Plug n Play cards Run this program once before the hardware is installed in the computer to
24. volts Now again observe the phase shift at pin 5 of the signal processing chip The oscilloscope should show a pattern similar to that from step 5 except now it should be of opposite phase Any displacement between phases should be quite small If there is any again adjust the phase shift potentiometer but this time adjust to correct about one half of the displacement between halves of the rectified sine wave pattern It may be necessary to repeat steps 5 and 8 several times to achieve minimum but equal positive and negative phase shift error Repeat step 4 FULL SCALE ADJUST Position the LVDT sensor for the desired maximum positive displacement The output on the monitor should read less than positive full scale Adjust the LVDT sensor for maximum negative displacement and check to see that the output on the monitor reads less than negative full scale The object now is to set the gain of the LVDT 8 so that full sensor travel produces full scale output in both positive and negative directions If the gain adjust potentiometer e g RP2 for channel 0 will not accomplish this change the jumper from the G1 2 position to the G2 4 position and try again Now check for linearity at 0 5 and at 0 0 times full scale The zero adjust potentiometer e g RP1 for channel 0 may be used to balance small differences between positive and negative displacements If that pot is adjusted then the gain adjust pot e g RP2 for channel 0 may now require slig
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