Audio Precision - Application Note (2-1989)- SYS
Contents
1. i T EREA AEE EA p BEE OEE NE PE CPE E EELEE Ricci E EES AE E E E EEE E EE AE EES E ER Sis C at i to Figure 27 LDR Resistance vs LED Current Digital Stimulus DC Measurements D to A Converter Testing The value of the digital output word of the DCX 127 can also be varied during a test Select DCX DIGOUT as SOURCE 1 Units may be selected as DEC decimal HEX hexadecimal or h x where the decimal value is scaled by the h scale factor entered in the DIGITALOUT section of the DCX 127 control panel START STOP and STEPS values may be entered as desired to control the range and step size Data presented to the connector can be formatted in one of two formats 8 4 2 1 BCD or two s complement 2sC which is binary plus sign Page 10 Audio Precision Inc SHEEP TEST DEFINITIONS EEP SETTLING press F9 to sweep cx DHMH TOLERANCE RESOLUTION AMPL 1 6086 x 188 8 nv LUL 1 888 z 25 66 uU THD 3 888 x 8 898887 z IMD 3 688 8 88883 x 8 88828 Hz 8 88828 x n 568 8 aU 188 8 ma z 1 888 LSB 8 58 DEG 688 8088 mdc 688 88 mUdc 18 LIN SCALE f 3 277 RANGE RATE 6 sec DCX NONE GRAPH TOP OFF BOTTOM OFF 8 LOG SOURCE 1 DCX START 28088 DEC STOP 2668 DEC 8 LIN DC OUT 8 8 DC OUT 2 8 8 DIGITAL IN SCALE g 1 888 RATE 32 sec DIGITALOUT 8 SCALE h 1 808 eee 3 SAMPLES DELAY 18 88 msec TIMEOUT 4 68 sec 25 OFF 8 STEPS2. SYS 127 APPLICATIONS TABLE OF CONTENTS COMPUTE LINEARITY Function 11 Overview of S1 EXE Software 0 0 0 0 cece eee 2 Single Point DC and Resistance Measurements PANES E seeker een E 3 4 DC or Resistance Measurements vs Time 6 Stimulus Response DC Measurements 7 9 e o e e e e o e o Measuring Resistance While Varying Voltage Digital Stimulus DC Measurements D to A Converter TESNE eine a a cand N a aaraa LU DC Stimulus Digital Measurements A to D Converter TESINE aene eters ates le a a e E eters Digital Stimulus Digital Measurements Control and Communications with External Devices Replacing the Computer Keyboard Adding AC and Audio Test Capability oo 0 o SPeCiiCaliOus ooer yas oak oe Wy ie ee AGO AeA 12 13 13 14 14 15 SYS 127 Applications Audio Precision Inc SYS 127 APPLICATIONS This applications note deals with dc resistance and digital tests and control which can be done automatically and graphically with the SYS 127 It is not intended to be a comprehensive treatment of all the types of tests which could be done with this instrument Instead the purpose of this note is to stimulate the reader s ideas in his or her own applications area by discussing a number of specific ex amples The SYS 127 consists of the Audio Precision DCX 127 multi function de and d
3. RANGE AUTO RATE 2 8 88887 x 8 868083 x Z 8 808020 Hz 8 889028 x 586 8 aV 108 8 m 1 668 LSB 8 58 DEG 18 6 sec DCX NONE GRAPH TOP OFF BOTTOM OFF 6 LOG 8 8 8 8 Vdc DC OUT 1 DC OUT 2 DIGITAL IN DEC SCALE g 1 688 2sC RATE 32 sec DIGITALOUT 6 DEC SCALE h 1 008 2sC SOURCE 1 BCX DCOUT1 ST 8 8 EXPONENTIAL Vde STOP 1 808008 Vdc 8 LIN 3 STEPS 18 TIMEOUT 4 68 OFF DEC DEC DEC PORT OUT A 6 B B EXT SOURCE 3 MIN LUL 18 88 C 8 MONO GRAPH GATE DELAY 56 88 msec dc FV OHMS 2 OFF To change setting use SPACE har DM Units To select another field use arrow keys Figure 3 DCX 127 Sweep Test Definitions and Sweep Settling Panels SYS 127 Applications The DCX 127 control and display panel is displayed at the left of the screen The SWEEP TEST DEFINITIONS panel is displayed at the screen center and the SWEEP SET TLING panel at screen right For simple real time setting of the DCX 127 dc or digital stimulus and simple observation of the dc resistance or digital measurements only the DCX 127 panel is necessary The SWEEP TEST DEFINITIONS panel permits setup of sweeps of dc or digital stimulus and selection of which measurements will display as lines on a graph when the F9 function key is pressed to start a test This panel also per mits flexible selection of units and graphic coordina
4. ORE o t OEE ra ANR CSR sce Hr ONEA ADOD OED SoHE HOMO TERS He CONN tec taa Dee amao aman aa i de aS aea aana ri a a ry gt H Se cesenmnesiseninen casas vs ooma rosaman Ap A BETRA ee ee ce en eas e e ENS t pam e oe aama ACE aoaea o e amn aeae t N R Raga a E a aaa a aaa a Py h p 59 sos oam so renano n es man 1H gum Hs ERIE eee taraa sera Seempaneosenmnsteennentiiamnatatehene Seabaeuntnnbmnansiemeemensuamastnnanennenonennsneautersanemmestosenensistesmasetiemmameummaniommeennester cammestimmemnanmatmemmennenmett p gt e s 4 a Brema amem i me a aone ss mamn escent mun ee samaa anea oes a s o aN CSREES 16 SURED te AEE RDS GP MESH OER MARS HSE HO SHES oon NER Sos UES CS SONNETS eRIR SRDS 3 x 1 H e s Fperra eama semn rerama soomaa aed cremate oneness omnes rocca eeraa a emnen eeaeee sarane PaE E eenamnancemasscemssmaenil t a 2 a t a z e e aane ananda aeaa eaaa aana ee eel ry p 3 3 p s 4 2 gt p 3 s 4 a s x s i a8 eseaneersausersstes rem awonna erte nan aenn stm sella 2 30 2 80 1 50 1 88 588m 8 8 t t a s Figure FET Resistance vs Gate Voltage SYS 127 Applications Figure 23 shows the setup panels saved as LDR RES TST on the diskette Fig
5. and STEPS At DATA 1 DCX DIGIN is selected For graphic display DEC decimal or g x scaled decimal may be selected as units with any desired GRAPH TOP and BOTTOM HEX hexadecimal notation may also be selected if tabular dis EEP SETTLING LOCAL SWEEP TEST DEFINITIONS press F9 to sweep DCX TOLERANCE RESOLUTION AMPL 1 800 188 8 nU 25 68 wl 8 88087 x 8 880863 x z 6 80826 Hz 8 89828 x 588 0 wl z 108 8 mf z 1 668 LSB 8 56 DEG DATA 1 DCX GRAPH TOP 3289 BEC 3289 DEC 18 LIN DCX Vde mn OFFSET f 0 8 i 808 AUTO 6 sec V c DIGITAL IN 8 8 gix DCX 1 808008 Vdc STOP 1 68608 Vdc 8 LIN 168 OFF SCALE g 304 0 uZsC RATE EXTERN DIGITALOUT 8 DEC SCALE h 1 808 2sC PORT OUT A 6 _ DEC B 8 DEC c8 DEC EXPONENTIAL 3 SAMPLES 10 08 msec SETTLING DATA DELAY TIMEOUT 4 08 sec STEPS TABLE EXT SOURCE 3 SAMPLES MIN LUL 16 08 mV MONO GRAPH DISPLAY GATE DELAY 2 668 sec print MEN NONE To change setting use SPACE bar Primary moasuroment To return to menu press the Isc key Figure 31 Setup Panels A D Converter Linearity Tests Page 12 Audio Precision Inc A D OUTPUT bits vs INPUT Volts 16 OCT 87 06 48 37 hin Aan hin on Tie Figure 32 A D Converter Linearity Test play is selected at the bottom of the panel DISPLAY TABLE at the bottom of the SWEEP TEST DEFINITIONS panel Figure 31 is a
6. cess Coupled with screen and logic output capabilities an automatic procedure can thus signal the pass fail decision to an operator via PC screen or separate annunciator or can even control a device handler See the User s Manual for more details CELLI9 20 JUL 88 12 46 28 NONECOFF DMM Vde OFF 1 38578 Vdc Figure 10 Example Screen Display Passing CHELLIS 28 JUL 88 12 46 28 NOKECOFF DMM Vde OFF 997877 Vde below 1 88868 Figure 11 Example Screen Display Failing Page 5 SYS 127 Applications Simple single point measurements of voltage or resistance with limits comparisons are perhaps the most common ap plication of the SYS 127 Checking dc power supply vol tages amplifier offset voltages battery voltages resistance values and dozens of other common applications are typical of this operation Multiple tests on the same device can be linked together into an automatic procedure Prompting messages to the operator may be interspersed as desired See the Procedures chapter of the User s Manual for more information on creating procedures DC or Resistance Measurements vs Time Sometimes it is necessary to measure a dc voltage versus time One example is testing the charge lifetime of a cell or battery while connected to a specific load resistance Another example is stability testing of power supplies while load input voltage or environmental conditions such as temperature are varied For measurements v
7. for Ni Cd Battery Test Audio Precision Inc sug aca NICD LO DHMCVde vs TIMEGoin 26 JUL 88 15 84 80 Figure 15 Graph of Limit File for Ni Cd Battery Discharge Test ten neni Ap L 2000 tee sce va bom een atte i menm namn eeens en ramet j ees eens oo ee rnd i i i Digo PRECISION PL DMM Udc vs TIMECmin 20 JUL 88 15 04 00 L G BOG Ermia mm snmmo mm s amm e man sea eaea ae a a aa e a a m a ee 1 400 Senne E oe AE E A E EESE A E E et Soren f i BE ea 40 wie 68 CET na Tee ee wi ite ii Q Figure 16 Battery Life Test with Limit File Displayed via lt Alt gt F7 Keystroke is an example of the NiCd battery life test from Figure 13 with the limit file of Figure 14 attached This example limit file is storedd as DCTIMELO LIM Stimulus Response DC Measurements In addition to measuring dc at a single instant or versus time dc voltage or resistance may be measured as a func tion of a stepped dc voltage stimulus Examples include testing the dc transfer characteristics of FETs linear ic s bipolar transistors opto isolators and varistors or other non linear resistors SYS 127 Applications Nested Sweeps The two dc outputs of the DCX 127 can be particularly valuable in such testing with one driving one junction or port while a second controls another junction or serves as a power supply S1 software permits a feature known as nested sweeps
8. logarith mic or linear relationship of the bargraph to the data are selected at the DATA 1 area near the top of the SWEEP TEST DEFINITIONS panel See Figure 5 for an example bargraph display The rate of updating of the bargraph is controlled by the 6 second vs 25 second rate selection for the DCX 127 panel numeric display selected on the DCX 127 panel The faster rate provides more rapid feedback for making adjustments but the slower rate provides better resolution for critical tests Limits In automated testing it is often desired to have the com puter compare a measurement to allowable performance limits and make a decision as to whether to accept the result Limit files are easily created in S1 software in the Edit Data mode The following discussion is an overview of limits file creation and use see the User s Manual for more details Load the test file to which limits will be attached and press lt Esc gt Edit Data Figure 6 shows a typical result with the column heads plus data if the F9 key has been pressed Move the cursor into the second line below the column heads Use the delete key or block delete capability F6 lt Ctrl gt lt PgDn gt F6 to erase any data there Type in a zero Audio Precision Inc 1 31769991 1668 Figure 6 Example of Edit Data Display After Single Point Measurement and comma for the SOURCE 1 column under the heading OFF and the allowable upper limit for the measurement in the s
9. t s H H BBuU bmn ett ieee a a a a eed i i Bau a aar IES HD 1FHMEED eS EINES ACPD 59 REEED OPV SENG 708 SUED SEP S a SERED POGIEED OOS T IEEE 1 OSU CORTES S Bu e a aaa aaa a a a a Figure 29 Re Graphed After Use of COMPUTE LINEARITY unction COMPUTE LINEARITY Function Linearity is difficult to accurately determine from a graph such as Figure 29 since it covers such a wide dynamic range The limited pixel resolution of the PC display in fact obscures any small deviation from linearity which may exist S1 software contains a powerful COMPUTE LINEARITY menu command created expressly for such applications In voking this command causes a straight line to be created which is the best fit to the data or any specified sub section of the data Each data point is then subtracted from this straight line Since this computation replaces the original data the raw data should be saved via the Save Test com mand before COMPUTE LINEARITY is invoked if you wish to have further access to the original data After using the COMPUTE LINEARITY command the graph sen Ativity may be greatly magnified by changing the GRAPH TOP and BOTTOM values at DATA 1 Figure 30 shows the data from Figure 29 after using the COMPUTE LINEARITY command and selecting new graphic coor dinates to display the deviation from perfect linearity Dis play system resolution is now not a limitation Lim
10. 17 Block Diagram FET Characteristic Testing Page 7 SYS 127 Applications Audio Precision Inc SHEEP TEST DEFINITIONS press F9 to sweep DATA 1L DCX DN GRAPH TOP 18 088 mf BOTTOM 8 8 f V DIVS DCX FET CHAR 89 JUN 88 86 26 55 Dede COUT Vac 386 888 wdc 2 7888 Vdc 408 688 wWde 2 7888 Vdc 428 088 wdc 2 7088 Vdc 438 888 Udc 2 7888 Vdc OFFSET f 8 8 SCALE f RANGE 6 sec AUTO SOURCE Z DCX DC OUT 1 2 6868 Vdc DC OUT 2 8 68088 Vdc Vdc Vac 28 880 we 2 4888 Vdc 1 25088 mdc 2 4888 Vdc i 1 73888 mdc 2 4888 Vdc 758 808 mdc 2 82880 mdc 2 4888 Vde Figure 20 Tabular Display of Data at a Transition Point in a Nested Sweep Series 18 DIGITAL IN DEC SCALE g 1 889 2sC 32 sec DCX RATE DIGITALOUT 8 DEC SCALE h 1 868 2sC 5 68888 Vdc 8 LIN DEC DEC DEC 26 OFF STEPS TABLE DISPLAY MONO GRAPH GATE DELAY 58 88 msec To change setting use digit keys fix SCALE x OFFSET To return to menu press the Esc key _ Figure 18 Setup Panels for FET Characteristic Testing SWEEP TEST DEFINITIONS press F9 to sweep DATA 1 aaa DMM EE v auno PRECISION m au sures mA oo ine y Lop different Vg my i i i Baa 6 sec SOURCE 2 DCX GRAPH TOP 6 8 Ude BOTTOM 3 8888 Udc STEPS 18 LIN 2 8886 Vdc 8 88888 Vdc DEC SCALE g 1 888 2sC RATE 32 sec DIGITALOUT 8 SCALE h 1 986
11. 8 2sC DCX DCOUT2 START 1 8888 Vdc STOP 1 88089 Vdc 8 LIN 28 PORT OUT A 8 DEC B 8 OFF DEC Cc 8 DEC MONO GRAPH DISPLAY GATE DELAY 58 88 msec To change setting use digit keys Expected maximum for qraph To return to menu press the Esc key Figure 19 Family of Curves of FET Characteristics Figure 21 Setup Panels for Measuring FET Characteristics Around Zero Volts the gate voltage is swept between 0 and 3 as SOURCE 2 while the source supply is stepped from 0O to 5V by SOURCE 1 This example test is stored on the companion diskette as FET CHAR TST Figure 19 shows the result This data could be saved to disk for a number of different FETs with the Append Test command or graphic overlay capability lt Alt gt F8 F8 then used to compare devices for matching When it is desired to know exactly which SOURCE 2 values correspond to the various curves change to DIS PLAY TABLE and press F7 Use F10 pause key to Suspend the data scrolling as desired Figure 20 shows a section of the resulting display at the transition between two SOURCE 2 values Figure 22 Graph of FE TOTEE Around Zero Volts Page 8 Audio Precision Inc To examine the characteristics around zero volts Figure 21 shows a panel setup and Figure 22 the resulting graph The display may be expanded for greater detail after taking data This example is saved as FET ZERO TST on the dis kette Measuring Resistance While V
12. TABLE EXT SOURCE 3 SAMPLES MIN LVL 16 88 mV DISPLAY MONO GRAPH GATE DELAY 3 888 BCOUT1 DCOUT2 TKS NONE To change setting use SPACE bar Sweep stimulus To return to menu press the Esc key Figure 28 Setup Panels D A Converter Linearity Test Static dc linearity testing of D to A converters is a prin cipal application for digital stimulus and dc measurements Note that dynamic testing is beyond the DCX capabilities since the digital output update rate is limited to about 30 changes second and the maximum dc meter reading rate is 25 readings second 6 second for maximum resolution Dynamic testing of converters is possible with the new DSP capability of System One contact Audio Precision for more details Figure 28 shows the control panel setup for a digital sweep around zero for a 16 bit D to A converter full scale range 32768 to 32768 Figure 29 is a graph from such a test This setup is stored as D TO A TST on the companion diskette AUDIO PRECISION D A dials cs vs bias do hits Figure 29 D A Converter Linearily Audio Precision Inc AUDIO PRECISION Deviation from Linearity Volts vs Digital Input bits 1 886n aR a a aa a Se laaa saer e acm 4 H i d k 2 3 0 o ff emera umesomea servcerreemme semamreemparrecqeae vtmannertaneatseenou ioman osann ses anmone menom ema aeaii eeen aoa senmana sf armene aoso reram monardo amc re saaa rear e itean G ry ry s
13. arying Voltage Many devices including FETs and LDRs light dependent resistors exhibit a variable resistance as a function of an ap plied control voltage or current The DCX 127 ohmmeter can be used to measure the resistance while the voltage of me of the DC outputs is varied SWEEP TEST DEFINITIONS press F9 to sweep OHMS DATA 1 DCX DMN 2 886 kOHM 188 8 OHM 18 LOG pet OFFSET f 0 8 SCALE f 166 6 RANGE 26 88 RATE 6 sec BOTTON DIVS SOURCE 2 DCX DC OUT 1 8 8 U DC OUT 2 8 88886 Vdc DIGITAL IN DEC SCALE g 1 888 2sC DCX 8 8 RATE 32 sec s Vde DIGITALOUT 8 DEC STOP 2 5880 Vde SCALE h 1 888 2sC DIUS 8B LIN 18 OFF PORT OUT A 8 DEC Ba DEC C 8 DEC MONO GRAPH GATE DELAY 58 68 msec AUTO To change setting use SPACE har DMM Range Units To return to menu press the Esc key Figure 23 Setup Panels for Measuring FET Drain Source Resistance as a Function of Gate Voltage sesam os mdh se HEE ioe antan L P MIME CREE SNES HOE LOMAS HORN FUER ES FSIS ORE LORD 10t BRRR t Ehlers ALOT 2A STEAD OF OEBE ORR ta SIDER Ne IN 4 e f Ap p a a i e 4 a gt bd J ry N e a s ry J e ikem eerste sma tems me ems ements tt semen isaac annem ents tte Bessam escent rs temas Rigen so sammon terete amam too Aad 1a ORD eo i MANA oa t
14. ch is only posi tive on either the digital or dc axis limit files must be created with sufficient intermediate points that the dif ference between logarithmic and linear interpolation is neg ligible With tight limits this may lead to a very high point density It may also be possible to create a two point limit file with one end below zero in order to force linear inter polation even when all data will be at positive values Limit testing after use of COMPUTE LINEARITY is probably a better solution in most cases For use before COMPUTE LINEARITY upper and lower linearity limits must be diagonal lines After COMPUTE LINEARITY the data represents deviation from perfect linearity and the appropriate limit files may be simply horizontal lines Depending upon the application it may also be appropriate to have limits after COMPUTE LINEARITY which are tightest near zero and increase in both directions away from zero in a bow tie or butterfly shape DC Meter Resolution Limitations The resolution of the DCX 127 digital voltmeter depends upon which range is in use Resolution on the 200 mV range is 10 microvolts for example while on the 20 Volt range it is one millivolt A 16 bit D to A converter with a 5 Volt dc output range for example has a theoretical transfer characteristic of 10 V 65536 states or about 152 microvolts output change for a one LSB change in input At Output values within 200 mV of zero the dc voltmeter resolu
15. dc or f V must be selected on the DCX 127 panel if DATA 1 is to be selected as dc voltage Example single point test files for measuring voltage and resistance are stored on the diskette under the names SING VDC TST and SING OHM TST When the selections are made press F9 for a measure ment The name of the test date and time and the measure ment will be displayed on the screen see Figure 4 To save the setup or data lt Esc gt to the menu use the Save Test command and supply an appropriate file name to avoid over writing the STD TST file automatically loaded by the DCX PRO procedure If we were setting up a battery cell test for a model 19 cell for example we might select a name such as CELL19 S1 software will automatically supply the TST file extension when lt Enter gt is pressed If you were now to re display the test result by pressing the F7 STD 28 JUL 88 12 46 28 NONEC OFF DHMCVde OFF 1 31778 Vdc Figure 4 Screen Display of Single Point Measurement Page 4 Audio Precision Inc 1 2167 Vdc NN 2167 sax 1 2167 ee 8 8 2 B88 Figure 5 Bargraph Display of DCX 127 Measurements function key the display would be identical to Figure 4 ex cept for the new test name which you supplied CELL19 TST is stored on the diskette as an example The measurement may also be displayed on the computer screen in analog bargraph fashion by pressing the F2 func tion key The end points of the bargraph and the
16. econd column see Figure 7 lt Esc gt to the menu select Save Limit and supply a name which will identify both the name of the test and the fact that this is an upper limit file For a battery cell test an example name might be ELL19UP lt Enter gt S1 software will automatically supply the LIM file extension and save the result as CELLI9UP LIM To create the lower limit press Edit Data and replace the upper limit value in the second column second row with the lower limit value see Figure 8 lt Esc gt and Save Limit as for example CELL19LO LIM CELLI9UP LIM and CELL19LO LIM are stored on the diskette as examples To attach these two limit files to the test file use lt Esc gt Load Test and the cursor keys to select and re load the CELL19 TST test Then use the Names Upper command place the cursor on CELL19UP LIM and press lt Enter gt Use Names Lower select CELL19LO LIM and press lt Enter gt to specify the lower limit To verify that the files are properly attached select Names you should see a dis play similar to Figure 9 This shows the test name and limit file names The test file must now be re saved with these limit file names attached in place of the original version of CELL19 TST Press lt Esc gt Save Test lt Enter gt and press Y to approve of the software over writing the original test version which did not have limit files specified a es Pre Figure 8 Example Lower Limit File SYS 127 Applica
17. enu selections such as PANEL are single level The menu is used primarily for computer intensive actions such as loading a test setup from disk into memory saving test setups or data to disk linking together multiple tests into procedures attaching limit files to tests making temporary exits to the computer operating system to run other programs during a procedure etc Selection of menu items is done in either of two fashions ne is by using the space bar to move the inverse video cur oor onto the desired item then pressing the lt Enter gt key The second method is simply to press the key corresponding to the first character of the menu item lt L gt for Load lt T gt for Test etc While the menu is used for computer oriented actions PANEL mode is used to actually control the DCX 127 in strument and to display spot measurements If the software was loaded with the DCX or DCXH batch file process described above or if the procedure DCX PRO was run after software startup the panels displayed when PANEL is selected will be as shown in Figure 3 If other panels have accidentally or deliberately been displayed load and run the procedure DCX PRO to restore these three panels to the screen SWEEP TEST DEFINITIONS SHEEP SETTLING press F9 to sweep DATA 1 DMM GRAPH TOP 10 880088 Vdc BOTTOM 18 8808 Vde LIN POR TOLERANCE RESOLUTION AMPL 1 666 108 8 nY 25 88 uU b Qo x MH OFFSET f 6 8 SCALE f 1 8
18. ersus time change the SOURCE 1 selections near the bottom of the SWEEP TEST DEFINI TIONS panel to EXTERN TIME Fields will then appear for the START and STOP values Units of seconds minutes or hours may be selected LIN would normally be selected for the horizontal axis time calibration but LOG could be selected to space measurement samples logarithmi cally in time Figure 12 shows an example panel for testing NiCd rechargeable batteries with O and 180 minutes selected as the START and STOP times Enter a value for STEPS which will produce data samples of the desired fre quency during the test For the example shown the 180 minute duration and 720 STEPS will cause a reading to be taken every 15 seconds At DATA 1 select GRAPH TOP and BOTTOM values to properly display the expected volt age range over the life of the test Press F9 to start the test Figure 13 is an example of a NiCd battery discharge This test is stored as DCVSTIME TST on the companion dis kette Limit files of any desired shape may be created for tests with a swept SOURCE 1 value in a manner similar to single point limits described above For the NiCd battery test the Edit Data command could be used to enter values such as shown in Figure 14 Note that SOURCE 1 values are now required in the first column rather than the 0 entered for single point measurements The limit file may be graphically displayed by pressing lt Esc gt F7 see Figure Page 6 Audio P
19. igital input output instrument plus the interface card cable and comprehensive software pack age necessary to operate it from an IBM PC XT AT or 386 compatible computer The software requires 640k memory and a CGA EGA VGA or Hercules monochrome graphics display system It may be used with one or more diskette and or hard disk drives A math co processor is highly recommended for fastest operating speeds but is not required The DCX 127 includes a 4 1 2 digit autoranging dc voltmeter ohmmeter two independently controllable precision voltage sources variable across a 10 5 Volt dc range with 20 microvolt resolution 21 bit plus sign parallel digital input and output words and 24 bits of control logic outputs plus several other features Digital I O and control logic outputs are LSTTL compatible For specifications see the last two pages of this note A comprehensive software package named S1 EXE S1H EXE for the Hercules version is included as part of the SYS 127 This software referred to as S1 in the remainder of this note is menu panel graph oriented No knowledge of any computer programming language is re quired nor is prior experience in programming The software permits real time measurements to be viewed in either analog bargraph or numeric display forms It also permits real time graphs of one or two simultaneous measurements to be plotted against a swept dc or digital stimulus or against time in chart recorder fashio
20. ional definitions to the switches Audio Precision Inc A macro may for example load and run a procedure which fully tests a given device and makes a go no go decision on its acceptability With this type of usage the computer monitor could even be eliminated and Pass Fail could be indicated by lighted annunciators driven off DCX 127 ports A B or C The operator s choices may be limited to RUN TEST A RUN TEST B and HALT Switches could also be defined as equivalent to the four cursor control arrows spacebar lt Enter gt key lt Esc gt key and F1 procedure abort key In this case the operator would have full ability to load and run any procedure shown in the procedure directory but without the error or editing possibilities of a full keyboard See the Custom Keyboard section of the DCX 127 chapter of the User s Manual for more details Adding AC and Audio Test Capability The DCX 127 provides only dc and digital stimulus and measurement capability For applications which additional ly require measurement of ac voltage frequency phase har monic and intermodulation distortion wow and flutter and generation of sinewaves up to 200 kHz squarewaves sine bursts and white or pink noise contact Audio Precision for additional information on the complete System One test sys tem which is controlled from the same digital interface and software The new DSP capability of System One will also permit dynamic testi
21. it files can be attached to D to A converter tests for use either before or after a COMPUTE LINEARITY cal culation Proper application of S1 software s limits capability for multiple point tests requires an understanding of how it interpolates between points in a limit file in order to compare a data reading At each data point S1 software looks in the limit file for the nearest point with a higher SOURCE 1 value to the right in graphic terms and the nearest point with a lower SOURCE 1 value to the left SYS 127 Applications The software then performs an interpolation between those two limit file points in order to obtain a single value to which to compare the data point If the SOURCE 1 horizontal values of both limit file points are positive S1 software performs a logarithmic horizontal interpolation If either point is zero or negative logarithmic interpolation is not possible and a linear interpolation is performed Similarly the vertical DATA 1 or DATA 2 interpolation is performed logarithmically if both points have positive vertical values and linearly if either is zero or negative In the case of D to A and A to D converters logarithmic interpolation is rarely appropriate If the converter is tested over a range which includes zero linear interpolation is automatically forced by creating a limit file with only two points one at the negative and one at the positive extreme If the converter is tested across a range whi
22. n Any test setup can be saved to disk for later use Data can be saved to disk and later retrieved for display in color graphic monochrome graphic or tabular formats Multiple tests can be linked together into complete test procedures by a keystroke learn mode which requires no programming ex perience Limits can be created and attached to any test for go no go results comparison Graphic or hard copy printout can be made to economical dot matrix printers at the touch Page 2 of a key or automatically during a procedure The DCX 127 additionally has features which permit replacing the computer keyboard with a simple keypad or a few switches in those applications where a full computer keyboard may be intimidating to unskilled operators This applications note will discuss many of the capabilities of the SYS 127 and will show examples of each class of ap plications Many other applications will be similar to those discussed here and the test setups and procedures can be patterned on those shown in this note Overview of S1 EXE Software The software furnished with an SYS 127 was developed to control Audio Precision s comprehensive System One audio test system of which the DCX 127 is one optional com ponent There are therefore many features of the software which are not relevant to DCX 127 applications They will not impede DCX 127 operation however S1 EXE software control capability includes a single line menu at the bo
23. n the panel have been rendered inoperative by punching them out To punch out a field such as the PORT OUT A field place the cursor on that field and press lt Alt gt P The video characteristics used to display that field will change depending on the type of display system and monitor you have When one or more fields have been punched out the file may only be saved as an Overlay file by the Save Over lay command When loaded an overlay file functions iden tically to a test file except for the punched out fields Punched out fields simply maintain the previous condition of that field See the Overlay section of the Procedures chapter of the User s Manual for more details Replacing the Computer Keyboard In Quality Assurance and production test applications the operators of a test system are frequently not trained tech nicians or engineers A PC keyboard may be unnecessarily complex for such operators possibly intimidating them and producing error opportunities The computer keyboard may be hidden or entirely discon nected and replaced with a simple user furnished set of switches The DCX 127 Program Control Input connector permits connection of up to eight normally open switches A momentary connection of any of these switches to ground causes a previously recorded series of keystrokes to be ex ecuted These keystrokes are stored as macro files MAC different macro files may be created and loaded to give dif ferent funct
24. n example of a panel setup and Figure 32 the resulting graph from a test of an A to D converter See A TO D TST on the diskette for this test setup The COMPUTE LINEARITY function may be used for A to D converter testing in a manner analagous to D to A converter testing See Figure 33 for a re graph of Figure 32 after the COMPUTE LINEARITY operation Limit files may also be applied with the same considera tions as discussed earlier with regard to logarithmic vs linear interpolation Note that 1 s limit comparison is less than or equal to Therefore a device passes a test if its out put is exactly equal to the limit Exact equality of measure ment to limit is very unlikely when analog measurements are made and compared but quite possible when digital devices are measured since the device output resolution and the DCX 127 input resolution are identical A D OUTPUT a vs ao hia 16 OCT 87 06 48 37 AUDIO PRECISION 2 0 wae oda jin Fae m in I Pi Figure 33 A D Converter Deviation from Perfect Linearity Audio Precision Inc There is no analagous factor to different dc voltmeter resolution on different ranges when testing A to D con verters with the DCX 127 The dc outputs have a constant resolution of 20 microvolts or better across their full range and the digital input has a constant one LSB resolution Digital Stimulus Digital Measurements A digital device may be tested on a static dc stimulus response basis wi
25. n it The UTIL OUT command may also be used in connection with any port of the computer such as its parallel printer port serial COM1 or COM2 port or ports added by plug in accessory cards In this case the port address in decimal is used rather than the A B or C designations for the connectors on the DCX 127 The UTIL WAIT command can be used to synchronize an automatic procedure with a condition of an external device The UTIL WAIT command is invoked with a computer port address data word and optional data mask When a UTIL WAIT statement of a procedure is reached the procedure will pause until the specified data word logic condition as qualified by the optional data word mask appears In a typi cal application UTIL OUT is used to command an external device to go to a certain condition To obtain verification that the device has truly assumed the necessary condition UTIL WAIT may then be used to sense some ready in dication line of the device When the device signifies that it is ready the procedure moves on to its next line See the User s Manual for more information and examples Page 13 SYS 127 Applications Overlays If it is necessary to set the ports at some point in an automatic procedure and have those port conditions main tained during a succession of tests S1 software s Overlay capability must be used An overlay OVL file is identical to a test TST file except that one or more of the fields o
26. ng of A D and D A converters AUDIO PRECISION INC P O Box 2209 Beaverton OR 97075 503 627 0832 1 800 231 7350 FAX 503 641 8906 TELEX 283957 AUDIO UR Page 14
27. pattern at each port is set in one of two fashions by an entry on the DCX 127 panel or by use of the UTIL OUT command of the menu The DCX 127 panel is normally used to set the digital word at a port when the application calls for the word to be different for each different test Saving a test setup saves SYS 127 Applications the words specified at all three ports and loading a test res tores all the conditions specified in that test The word may be entered in the DCX 127 panel in either decimal DEC hexadecimal HEX or octal OCT format The UTIL OUT method of setting port values may be used when output conditions must be changed before a test is loaded or changed during an automatic procedure without loading another test Only the decimal format may be used with UTIL OUT It is important to understand the priorities between the DCX 127 panel and the UTIL OUT command in controlling ports A B and C When a test is loaded the settings in the test including a zero setting take priority over the previous condition of the ports whether that condition was estab lished by a previous test file or by the UTIL OUT com mand After a test has been loaded exiting to the menu and using the UTIL OUT command will override the settings on the DCX 127 panel Those changes will be visible on the DCX 127 panel after using UTIL OUT and returning to the panel If the test file were saved at that stage it would have the new settings stored i
28. recision Inc SHEEP TEST DEFINITIONS WEEP SETTLIN press F9 to sweep DATA 1 DCX DMN GRAPH TOP 2 88888 Ude BOTTON 8 8 Vde 16 LIN TOLERANCE RESOLUTION 188 8 wl 25 88 uV 8 88887 x 8 88883 x SCALE f 1 8 RANGE AUTO RATE 6 sec DATA 2 DCX DC OUT 1 8 8 Vde DC OUT 2 8 8 Vde OHMS 8 588 x D IN 8 888 x PHASE DEG SETTLING EXPONENTIAL DATA 3 SAMPLES DELAY 38 88 msec TIMEOUT 4 86 sec DIGITAL IN DEC SCALE g 1 888 2sC RATE 32 sec DIGITALOUT 8 DEC SCALE h 1 888 2sC DEC B8 DEC DEC EXT SOURCE 3 MIN LUL 18 88 SAMPLES MONO GRAPH aV GATE DELAY 56 88 msec FREQ LEVEL i To change setting use SPACE har Sweep stimulus To return to menu press the Esc key Figure 12 Setup Panels for Voltage vs Time Measurement AUDIO PRECISION Pi ee vs ee 2 BGB E 8000 a ero emesis H nn O an nemam messes ae or i on oj H 7 L 7 AE EE E E E O E Ly 4809 fn a a e eet ee me i E mai of Ni Cd Battery Voltage vs Time 15 for an example If this file were saved as a lower limit file and attached via the Names Lower command every data point taken during a test will be compared to a limit value interpolated from the nearest horizontal points in the limit file If desired an attached limit file may be graphed before or after a test is run by pressing lt Alt gt F7 Figure 16 Vde 1 28888888 i Figure 14 Lower Limit File
29. tes Real time bargraphs see Figure 5 may be displayed by pressing the F2 function key The SWEEP TEST DEFINI TIONS panel also controls the bargraph calibrations The SWEEP SETTLING panel controls how S1 software determines whether measurement results are sufficiently Steady state to retain and plot a measurement point The settling concept involves continually examining the stream of measurements furnished by the DCX 127 hardware Only when the several most recent measurements agree with one another within a tolerance window specified by the user on the SWEEP SETTLING panel will the software retain and plot the most recent point and move on to the next measurement Settling may be turned off when it is desired to plot every measurement regardless of data varia tions Additional capabilities and features of S1 software will be discussed as they apply to specific applications described below A comprehensive treatment of S1 software may be found in the User s Manual furnished with the SYS 127 system Single Point DC and Resistance Measurements Dc voltage up to 500 Volts can be measured with the DCX 127 Resolution of the voltmeter varies from 10 microvolts on the 200 mV range to 0 1 Volt on the 500 Volt range Resistances up to 2 5 Megohms can also be measured with resolution varying from 10 milliohms 200 Ohm range to 200 Ohms 2 Megohm range Four wire Kelvin connections may be made to the unknown device to reduce the infl
30. th the DCX 127 Since it is unlikely that such devices will have a linear digital transfer characteris tic across a range of contiguous digital states most such tests are likely to be spot measurements Thus logic cir cuitry can be tested one state at a time by applying a specific digital stimulus while measuring and comparing to limits the digital output Since a digital input digital output device is likely to have only one correct output state for a given input the upper limit and lower limit will typically be equal to one another and equal to the expected digital output word A single limit file may thus be saved and named both as upper and lower limit The format flexibility of S1 software can simplify testing of certain digital interface circuits Circuitry designed to drive BCD indicators can be easily tested by stimulating it with the DIGOUT signal in 2sC two s complement or bi nary format while measuring the device s output with the DIGIN capability in BCD format Control and Communications with External Devices The DCX 127 and S1 software provide capability for con trol of external devices via logic or by driving external relays Additional control of external devices and synchronization of procedures with external devices is pos sible by S1 software features using ports of the PC Three 8 bit latched output ports are located on the rear panel of the DCX 127 Each is a 9 pin D subminiature con nector The bit
31. ting Page 9 SYS 127 Applications SWEEP TEST DEFINITIONS SWEEP SETTLIN press F9 to sweep DATA 1 DCX DHA GRAPH TOP 288 8 kOHM 188 8 OHM 18 LOG DCX TOLERANCE RESOLUTION 188 8 wi 25 68 uV 8 68887 x 8 88883 x 8 88828 Hz 8 88828 x 5868 8 uU OHMS 6 588 x 108 6 al D IN 8 888 x 1 888 LSB PHASE 6 58 DEG DMM OFFSET f 8 8 SCALE f 108 8 RANGE RATE 6 sec SOURCE 2 DCX HONE GRAPH TOP OFF BOTTOM OFF STEPS 8 LOG DC OUT 1 8 8 Udc DC OUT Z 1 48888 Vdc DIGITAL IN DEC SCALE g 1 888 RATE 32 sec DIGITALOUT 8 SCALE h 1 888 SOURCE 1 DCX DCOUT1 START 16 8888 mUdc STOP 108 88808 Vde DIUS 8B LOG EXPONENTIAL 3 SAMPLES DELAY BCI T sec TIMEOUT 4 88 sec SETTLING DATA 38 OFF STEPS TABLE EXT SOURCE 3 SAMPLES MIN LUL 18 868 mV MONO GRAPH DISPLAY GATE DELAY 58 68 msec To change setting use digit keys Delay time before trigger To select another field use arrow keys Figure 26 Setup Panels LDR Tests eal opto isolator resistance LDR RES s ieee E ae EEE oee a a EE rN dp acs A E somone E E eden T E N E A A E O a E a Sor ond N t DBANIA A NUD da AADS HAS EAMT 941 AATA I HA ne farianten Sood Las onea o RENN OFC maman es SUEUR Ee een a eae ees deme A rs ie a z ee oe mec RiR Ld t penne i mejohe mietet j i menih ebi Font 4 bh et g R
32. tion of 10 microvolts is thus more than adequate At Page 11 SYS 127 Applications values greater than 1 999 Volts the meter will autorange to its 20 Volt range and the consequent one millivolt resolu tion will obscure errors smaller than approximately 6 LSBs Either of the DCX 127 s dc outputs can be inserted with jumper leads in series with the dc voltmeter input and set to a value which offsets part of the converter s output voltage This connection creates a differential voltmeter configura tion which measures the difference between the output of the D to A converter under test and the DCX 127 dc output If that difference is less than 200 mV the meter can range to its most sensitive range and use its full resolution To test a converter across its full range with adequate meter resolu tion in every case will thus require a series of test sweeps each with a different value of dc output voltage for meter offset in order to keep the meter on a range with acceptably high resolution DC Stimulus Digital Measurements A to D Converter Testing Testing devices such as A to D converters is conceptually similar to D to A converter testing in many ways Either of the dc outputs of the DCX 127 is used for stimulus while the digital output of the converter is connected to the DCX 127 digital input On the control panels SOURCE 1 is now selected as DCX DCOUT1 or DCOUTZ2 and appropriate voltage values entered for START STOP
33. tions AUDIO PRECISION wa aad bat w o o gt oy 3 w o 1 CELL19 TST CELL19UP LIM CELL19L0 LIM Upper Compare File Lower Compare File Sweep Source File Genifi Equalization File Compute Delta File Error Reporting File ee aximum Data Points 986 1 used Internal EQ Limit Sweep Points 288 aximum Edit Data Size 9217 181 used 0 in copy buffer aximum Edit Procedure Size 32478 6 used 6 in copy buffer aximum Edit Comment Size 32478 8 used 6 in copy buffer aximum Edit Hacro Size 7213 8 used B in copy buffer Bytes Reserved for DOS 32769 NAMES MJIN LOWER SWEEP GEN1 1 EQ ERROR FILE OFF TITLE RENAME TEST CLEAR DELTA Select file for upper compare limit AUDIO PRECISION SYSTEM ONE vi 68C Figure 9 Names Display When a tabular display test with limits attached is run F9 key the display will show any outside limits result Figures 10 and 11 are examples of both passing and failing tests The measurement and the limit value exceeded are both displayed in the case of failure Note that this is the simplest of several pass fail techniques in the software package S1 EXE software can also automatically write passing messages or failure data into an error summary file and one error summary file can be used for any number of tests in a complete procedure S1 EXE software can also take conditional action in a procedure upon failure or suc
34. ttom of the screen plus eight panels Only three of those panels are used in DCX 127 operation A companion diskette to this applications note contains a num ber of tests procedures and batch files The batch files DCX BAT or DCXH BAT may be used for maximum con venience in loading and using the SYS 127 If the software is started from the DOS prompt with the command DCX or DCXH for Hercules monochrome version software the corresponding batch file on the diskette loads S1 software and runs a procedure which selects the three relevant panels This process also loads a test file named STD TST standard test which has pre selected the DCX 127 as the stimulus source and measurement to be displayed for graphic testing The menu structure has two levels for most activities The top level CMD for COMMAND is reached from any screen via the lt Esc gt key see Figure 1 Selecting most items in the CMD menu causes a second level menu to be displayed for that particular action See Figure 2 for an il CHD FQ PANEL LOAD SAVE APPEND EDIT HELP XDOS DOS NAMES IF UTIL QUIT COMPUTE Run procedure test om qraphs AUDIO PRECISION SYSTEM ONE vi 68C Figure 1 Command Menu Audio Precision Inc LOAD PNY LIMIT SWEEP COMMENT PROCEDURE MACRO DATA EQ IMAGE OVERLAY Load entire test fron TST file AUDIO PRECISION SYSTEM ONE vi 68 Figure 2 Load Menu lustration of the LOAD menu obtained by selecting LOAD from the CMD menu Some CMD m
35. uence of lead resistance when measuring low values of resistance Page 3 SYS 127 Applications De or resistance measurement mode is selected in the top line of the DCX 127 panel see Figure 3 Dc voltage may be directly displayed in Volts and millivolts or f V may be selected With f V as units the actual dc measurement will be scaled and offset by the scale and offset values entered on the DCX 127 panel before display Similarly resistance may be displayed as Ohms or may be scaled and offset with f Q Offset and scaling are commonly required when the device being measured is a transducer such as a temperature or pressure sensor Appropriate selection of offset and scaling factors can then often produce a display directly in engineering units such as degrees or pounds per Square inch If it is desired to do more than simply observe readings on the DCX 127 panel the SWEEP TEST DEFINITIONS panel and certain function keys come into play For single point measurements of dc or resistance which can be com pared to limits saved to disk or printed select DCX NONE as SOURCE 1 at the bottom of the panel This mode automatically selects tabular display even if MONO GRAPH or COLOR GRAPH is selected and creates a single point measurement At DATA 1 select DCX then the desired dc or resistance mode To obtain resistance modes on the SWEEP TEST DEFINITIONS panel OHMS or f Q must have been selected on the DCX 127 panel Similarly V
36. ure 24 a representative graph of FET drain source resistance as the gate voltage is varied To prevent the ohmmeter from autoranging and thereby chang ing the voltage used for resistance measurements it should be fixed on an appropriate range In the example shown the meter was fixed on the 20 kilohm range Results are then valid only at relatively low resistances where the test volt age is small A light dependent resistor opto isolator consists of a light emitting diode LED and a photo sensitive resistor coupled optically inside an opaque package Figure 25 shows a connection diagram for the DCX 127 and an LDR DC output 1 is swept to vary current through the LED A 1 kilohm series resistor produces a 1 milliampere Volt relationship to the dc output 1 The DCX 127 ohmmeter measures the photo sensitive resistance To make the horizontal axis of the graph aproximately equal to LED cur rent DC output 2 was set to barely turn on the LED about 1 4 Volts as determined by monitoring the resistance while DC output 1 was at zero volts This approximately com pensates for the on voltage of the LED Figures 26 and 27 are the setup panels and a graph of this measurement Note that LDRs can have long time constants one second or greater at high resistances and thus can require settling delay values of one second or more on the SWEEP SET TLING panel for accurate measurements LDR Measurements Figure 25 Connection Diagram LDR Tes
37. which can create an entire family of curves in one test Stimulus parameters may be selected both at SOURCE 1 and at SOURCE 2 SOURCE 2 is an alternate selection to DATA 2 near the center of the SWEEP TEST DEFINITIONS panel When SOURCE 2 is selected the GRAPH BOTTOM value must be interpreted as SOURCE 2 START and GRAPH TOP must be inter preted as SOURCE 2 STOP The STEPS value deter mines the number of steps which SOURCE 2 will take be tween those end values The span between SOURCE 2 GRAPH BOTTOM and TOP will be divided into equal in crements for the steps if LIN is selected and into equal per centage steps if LOG is selected and if both values are positive When F9 is pressed SOURCE 2 is set to the starting GRAPH BOTTOM value and SOURCE 1 is stepped through its specified range SOURCE 2 is then in cremented one step towards its GRAPH TOP value and the SOURCE 1 sweep is repeated This process continues through the final SOURCE 1 sweep at the SOURCE 2 en ding GRAPH TOP value The result is a family of curves Figure 17 is the block diagram of the connections between the DCX 127 and a field effect transistor FET DC output 1 is used to control the gate voltage DC output 2 is used as the drain supply A 10 Ohm current sensing resistor is used between DC output 2 and the drain with the dc voltmeter measuring current by measuring the voltage drop across the resistor Figure 18 shows the setup panels where Figure
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