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Hardware for an electrical machines laboratory computer data acquisition system Jordan, James Ellwood 1970

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HARDWARE FOR AN ELECTRICAL MACHINES LABORATORY COMPUTER DATA ACQUISITION  SYSTEM  by JAMES ELLWOOD JORDAN B.Sc,  University  of Manitoba,  1968  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF  MASTER OF APPLIED SCIENCE  i n the Department of Electrical  We a c c e p t  Engineering  t h i s t h e s i s as conforming t o the required  Research  standard  Supervisor..  Members of Committee.  Head o f Department... <  Members of the Department of Electrical  Engineering  THE UNIVERSITY OF BRITISH COLUMBIA December,  1970  In  presenting  this  an a d v a n c e d  degree  the L i b r a r y  shall  1 f u r t h e r agree for  scholarly  by h i s of  this  written  thesis at  the U n i v e r s i t y  make  it  It  E-L^CRtCAU  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, C a n a d a  for  DEC.  J4/7Q  I agree  r e f e r e n c e and copying of  shall  that  not  copying  this  or  for  that  study. thesis or  publication  be a l l o w e d w i t h o u t my  E*)6lAiE£S>06  Columbia  requirements  by t h e Head o f my D e p a r t m e n t  is understood  f i n a n c i a l gain  the  B r i t i s h Columbia,  permission.  Department o f  pate  of  for extensive  p u r p o s e s may be g r a n t e d  for  fulfilment of  freely available  that permission  representatives. thesis  in p a r t i a l  ABSTRACT Hardware f o r an e l e c t r i c a l machines laboratory computer data a c q u i s i t i o n system i s considered. study of the r o l e of a computer  A survey of existing equipment and a  system i n laboratory i n s t r u c t i o n i s made  for  the UBC e l e c t r i c a l machines laboratory.  the  hardware required f o r a data a c q u i s i t i o n and processing system are ,  studied and a system configuration proposed.  From t h i s , s p e c i f i c a t i o n s f o r  Transducers for measuring  voltage and current waveforms on a machine are considered and designed. The performance of the transducers constructed i s evaluated i n two sets of measurements.  In the f i r s t set, measurement error, o f f s e t  drift,  common-mode r e j e c t i o n r a t i o , and frequency cutoff are measured for the transducer set (by i t s e l f ) . In the  Measurement errors are found to be less than 1% F.S.  the second set of measurements, a system similar to the one proposed for machines laboratory i s tested.  Results from this set of measurements  i n d i c a t e that the system design proposed i s workable.  (ii)  TABLE OF CONTENTS Page ABSTRACT  •  ••• ' i i  LIST OF ILLUSTRATIONS  -iv  LIST OF TABLES  • •  ACKNOWLEDGEMENT 1.  2.  5.  1  D e s c r i p t i o n o f System D e s i r e d Scope o f T h e s i s P r o j e c t  1 2 • •  System Study.... Input/Output D e v i c e Transmission Link Analog to D i g i t a l I n t e r f a c e Computers F i n a l System C o n f i g u r a t i o n . .  -  ••  TRANSDUCERS 3.1 3.2  4.  . .'  SYSTEM CONFIGURATION 2.1 2.2 2.3 2.4 2.5 2.6  3.  vi  INTRODUCTION 1.1 1.2  v  3 3 9 9 10 12 13 16  Proposed S p e c i f i c a t i o n s Transducer Design 3.2.1 C u r r e n t T r a n s d u c e r s 3.2.1.1 H a l l M u l t i p l i e r 3.2.1.2 C o n s t a n t - C u r r e n t Source 3.2.1.3 L e v e l A m p l i f i e r . 3.2.2 V o l t a g e T r a n s d u c e r s  16 16 17 17 . . . . 20 20 24  RESULTS  27  4.1  First  S e t o f Measurements  4.2  Second S e t of Measurements  CONCLUSIONS  27 29  AND SUGGESTIONS  30  APPENDIX A APPENDIX B  Current Transducer A m p l i f i e r Design.. V o l t a g e Transducer A m p l i f i e r Design  33 35  APPENDIX C  D e s c r i p t i o n of Tests  37  C l  T r a n s d u c e r s Only C.l.l Measurement E r r o r C.1.2 O f f s e t D r i f t C.1.3 Common-Mode R e j e c t i o n R a t i o C.1.4 Frequency Response  37 37 39 39 39  C.2  System T e s t  39  .  REFERENCES  '  (iii)  4  5  LIST OF  ILLUSTRATIONS  Figure  Page  2.1  B l o c k Diagram o f System  3.1  Current Transducer  3.2  Hall Multiplier  3.3  Current Regulator Configurations  3.4  Current Regulator  3.5  .....  Configuration  8 18 18  .  21 22  . D i f f e r e n t i a l A m p l i f i e r Design Design  22  3.6  Voltage Transducer  5.1  A Superior D i f f e r e n t i a l Amplifier  31  C.l  Measurement E r r o r T e s t  38  C.2  Offset D r i f t  38  C. 3  CMRR Measurement  38  C.4  F r e q u e n c y Response T e s t  40  C.5  System T e s t  40  C.6  Flow Chart  42  C.7  D a t a A c q u i s i t i o n Program L i s t i n g  43  C.8  I n t e r f a c e C h a r a c t e r i s t i c s Measurements  44  Test  (iv)  26  LIST OF TABLES Table  •  Page  2.1  Characteristics  o f Tamper E l e c t r i c a l Machine Sets  ^  2.2  C o n v e n t i o n a l Measuring  2.3  Interface Specifications  2.4  Computer S p e c i f i c a t i o n s  14  3.1  Hall Multiplier Specifications  19  3.2  Specifications  of F a i r c h i l d  23  3.3  Specifications  o f M o t o r o l a MC1741CG  4.1  Measured T r a n s d u c e r  Instruments  5 '  11  UA723C  Characteristics  (v)  •••  2  5  28  ACKNOWLEDGEMENT The  author would l i k e  to e x p r e s s h i s a p p r e c i a t i o n t o h i s  Dr. A. D. Moore, f o r guidance and a s s i s t a n c e d u r i n g B. J . K a b r i e l f o r r e a d i n g Appreciation Engineering  supervisor,  t h i s p r o j e c t , and to Dr.  the manuscript.  i s a l s o expressed to the s t a f f o f the E l e c t r i c a l  Department, UBC, f o r h e l p f u l a s s i s t a n c e , to f e l l o w s t u d e n t s f o r  proof-reading,  and e s p e c i a l l y to M i s s V e r o n i c a  Komczynski f o r t y p i n g t h e  thesis. The  work d e s c r i b e d  i n this  t h e s i s was c a r r i e d out under N a t i o n a l  Research C o u n c i l o f Canada g r a n t A-3357. f i n a n c i a l support  The author g r a t e f u l l y  r e c e i v e d i n t h e form o f N.R.C. P o s t g r a d u a t e  (vi)  acknowledges  Scholarships.  1  1.  INTRODUCTION  T h i s t h e s i s i s concerned  w i t h a proposed  o n - l i n e computer d a t a  a c q u i s i t i o n and p r o c e s s i n g system f o r an undergraduate laboratory. ital  electrical  The long-term o b j e c t i v e o f t h i s p r o j e c t i s t o i n t r o d u c e a d i g -  computer system i n t o the e d u c a t i o n a l environment o f a l a b o r a t o r y as an  i n s t r u c t i o n a l a i d as w e l l as a measurement and computation  1.1  machines  facility.  D e s c r i p t i o n o f System D e s i r e d The  system e n v i s a g e d  a c q u i r e measurement d a t a from  f o r the e l e c t r i c a l the e l e c t r i c a l  machines l a b o r a t o r y w i l l  machines and compute  experimental  results  f o r the u s e r s .  Such a system c o u l d c o n c e i v a b l y c o n s i s t o f a s m a l l  digital  computer, a s e t o f t r a n s d u c e r s f o r each machine, and some form o f  i n t e r f a c e between the t r a n s d u c e r s and computer.  The system developed  n o t r e p l a c e the e x i s t i n g measuring i n s t r u m e n t s .  Instead, i t w i l l  machines and meters to be connected of  s e t t i n g up the experiment  variables. as w e l l . with  The s t u d e n t s w i l l  the normal i n s t r u m e n t s  to r e t a i n the e d u c a t i o n a l v a l u e  and to p e r m i t v i s u a l m o n i t o r i n g o f the machine's  commence the experiment  can perform  at t h i s p o i n t .  o f the p r i n c i p l e s  the t e d i o u s t a s k o f c a l c u l a t i n g r e s u l t s  the experiment.  r e s u l t s as u s u a l .  compute the c o r r e c t v a l u e s f o r the experiment  can be checked  have demonstrated an u n d e r s t a n d i n g  role  by making measurements  and c a l c u l a t i n g e x p e r i m e n t a l  the computer w i l l  the s t u d e n t ' s r e s u l t s  as w e l l .  a l l o w the  I n t h i s way, the f a c i l i t y can be used i n an i n s t r u c t i o n a l  Simultaneously, and  normally  will  Once the s t u d e n t s  i n v o l v e d , t h e computer f o r the remainder o f  I f d e s i r e d , t u t o r i n g o f the s t u d e n t s c o u l d be i n c o r p o r a t e d  The t r a n s d u c e r s must be capable o f making measurements which are  as a c c u r a t e as those o b t a i n e d from  conventional instruments.  would be d e s i r a b l e t o measure i n p u t s w i t h  As w e l l , i t  f r e q u e n c i e s up to the n i n t h  2  harmonic o f 60 Hz. to be  studied.  to p e r m i t t r a n s i e n t s and  Such a system w i l l hence be  harmonic waveforms on  the machines  u s e f u l f o r general-purpose  e x p e r i m e n t a l work as w e l l as l a b o r a t o r y i n s t r u c t i o n .  1.2  Scope o f T h e s i s The  Project  f i r s t part of this  o f the system j u s t d e s c r i b e d .  t h e s i s p r o j e c t i s the study and s p e c i f i c a t i o n T h i s work i s p r e s e n t e d i n Chapter 2,  System  Configuration. The  second p a r t of t h i s p r o j e c t i s the development,  and  checkout of a s e t o f t r a n s d u c e r s  The  design  o f these t r a n s d u c e r s  In the l a s t p a r t , and  on a system s i m u l a t i n g  Results.  i n Chapter 3,  t e s t s were conducted on  determine t h e i r a c t u a l performance. i n Chapter 4,  f o r the e l e c t r i c a l machines  i s described  the one  construction,  the  laboratory.  Transducers.  transducers  developed  proposed f o r the machines l a b o r a t o r y Results  O f t h e s e t e s t s are  to  summarized  3  2. 2.1  System  SYSTEM CONFIGURATION  Study  The UBC  e l e c t r i c a l machines  laboratory consists p r i m a r i l y of s i x  e l e c t r i c a l machine s e t s , each c o m p r i s i n g an i n d u c t i o n machine, machine,  and a d.c. machine,  a l l on a common s h a f t .  p l i e d w i t h power from a 230 v o l t 60 Hz. a.c. bus.  The machines  The l a b o r a t o r y i s sup-  d.c. bus and a 208 v o l t  may  ( r . m . s . ) , 3-phase,  be connected i n v a r i o u s  u s i n g a p a t c h b o a r d arrangement by the e x p e r i m e n t e r . electrical characteristics  are summarized  i n Table  a synchronous  configurations  The d e t a i l s o f t h e i r 2.1.  A number o f i n s t r u m e n t s are n o r m a l l y used f o r making measurements on the e l e c t r i c a l machines.  P r i m a r i l y , a m u l t i m e t e r i s used f o r measuring  r e s i s t a n c e , v o l t a g e , and c u r r e n t  (up to 10 amperes).  A number o f ammeters  a r e a v a i l a b l e f o r measuring a.c. c u r r e n t s up to 300 amperes and d.c. up to 15 amperes.  As w e l l , c u r r e n t shunts and m i l l i v o l t m e t e r s  f o r measuring c u r r e n t s up to 1000  amperes.  Wattmeters  currents  are a v a i l a b l e  are used f o r measuring  e l e c t r i c a l power i n a number o f ranges up to 15 k i l o w a t t s .  The  o f the i n s t r u m e n t s a v a i l a b l e are b r i e f l y o u t l i n e d i n T a b l e 2.2.  specifications Of  particular  i n t e r e s t a r e the a c c u r a c y s p e c i f i c a t i o n s , most o f which a r e o f the o r d e r o f -1% F . S  F o r m e c h a n i c a l measurements, a s t r o b o s c o p e i s used t o measure s h a f t  V  angular v e l o c i t y  and a m e c h a n i c a l arm and s p r i n g b a l a n c e a r e used to measure  s h a f t torque. The m a j o r i t y o f experiments i n the e l e c t r i c a l machines i n v o l v e the measurement o f q u a n t i t i e s on o n l y one machine.  laboratory  However, a s i g n i f -  i c a n t number o f experiments use a second machine connected to the machine under t e s t .  By measuring  second machine, under t e s t  the e l e c t r i c a l power consumed o r g e n e r a t e d by the  the m e c h a n i c a l power produced o r absorbed by the machine  can be c a l c u l a t e d .  By p r o v i d i n g e x t r a t r a n s d u c e r s to measure  4  T a b l e 2.1:  (a)  CHARACTERISTICS OF TAMPER-ELECTRICAL MACHINE SETS  Steady S t a t e :  Wound Rotor I n d u c t i o n Motor  Synchronous Motor  D.C. Motor  RPM - 1690  RPM - 1760  RPM - 1800  H.P. - 2.5  H.P. - 2.5  K.W.  Arm. V o l t s - 2 3 0 VDC.  KVA - 2 . 0 .  Arm. F.L. Amps-10.3  Arm.  S t a t o r V o l t s - 2 0 8 , 30, S t a t o r F.L. Amps.-8.0  60 Hz.  - 1.6  Volts-120/208,  30, 60 Hz. R o t o r V o l t s - 274  Shunt F i e l d Volts  R o t o r Amps. - 4.3  Shunt Amps.  (b)  Field_  (2)  (3)  3  Q  ,58/.44  Arm. F . L . Amps-5.5 @ p.f.= 0.8 F i e l d V o l t s - .115 D.C. F i e l d Amps. - 1.2  Transients:  Description of Condition (1)  2  Induction Motor-Stator current f o r s t a r t - u p s w i t h n o - l o a d and s h o r t e d rotor I n d u c t i o n Motor-Rotor c u r r e n t f o r s t a r t - u p s w i t h n o - l o a d and s h o r t e d rotor Synchronous M o t o r - S t a t o r c u r r e n t for induction-like start-ups; I = 0. I n d u c t i o n Motor-connected as a synchronous motor f o r 10, 20, & 30 f a u l t c o n d i t i o n experiment D.C. Motor  Max. Measured Value  (unidirectional)  20  A.  24  Ar .  47  A.. -  20  A. • .  20  A., c u t o u t  *  f  (4)  (5)  5  T a b l e 2.2:  (a)  AVO-Meter: (i)  CONVENTIONAL MEASURING INSTRUMENTS  Model 8:  Ranges:  D.C.  Voltage:  1000, 500, 250, 100, 25, 10, 2.5 v o l t s  A.C.  Voltage:  1000, 250, 100, 25, 10, 2.5  D.C.  Current:  10, 1, .1; .01, .001, .000250, .000050 A.  A.C.  Current:  10, 2.5, 1.  Resistance: (ii)  Accuracy:  (iii)  Input  Voltage:  2% F.S.  D.C.  Current:  1% F.S.  2 /4 %F.S. 1  Requirements: All  (b)  .1, A.  0-2000, 0-200 K, 0-20 M Q.  D.C.  A.C. :  volts  D.C.  V o l t a g e Ranges:  20,000 Q/T. (50uA.for  full  deflection)  D.C.  C u r r e n t Ranges: P o t e n t i a l drop = 0.5 V. a t f u l l except 50 yA. range which absorbs. 125 mV.  A.C.  V o l t a g e Ranges: Above 100 V.+ 1000 QjV- (1 mA. f o r f u l l d e f l e c t i o n ) ; 25 V, consumes 4 mA,; 10 V. consumes 10 mA; 2.5 V. consumes 40 mA.  A.C.  C u r r e n t Ranges:  0.2 V. drop  A.C.  Ammeters:  (i)  Input Ranges and (number o f i n s t r u m e n t s ) :  load  a c r o s s t e r m i n a l s on a l l r a n g e s .  300 A.(2); 100 A. (1) ; 50 A.(7) ; 25 A. (2) ; 15 A. (2); 5/10 A. (8) ; 5 A . ( l ) ; 2.5/5 A . ( l ) ; 2 A . ( 3 ) ; 1.5/3 A . ( 1 ) ; 1 A . ( l ) ; . .25/.5 A.(2) (ii)  (c)  T y p i c a l Accuracy:  2% F.S.  A.C. V o l t m e t e r s : (i)  Input Ranges and (number o f i n s t r u m e n t s ) : 150/300/600 V. ( 2 ) ; 150/300 V. (14); 60/120 V. ( 1 ) ; 30/60 V. ( 3 ) ; 30 V . ( 2 ) ; 2.5/15/30/ 75 V. ( 1 ) ; 15/30 V . (1)  6 Table  (d)  2.2  (cont'd)  Clamp-on (i)  Ammeters:  Input  Ranges and (number o f i n s t r u m e n t s ) :  15/60/150/600 A . ( 1 ) ; 10/25/50/100/250/500  (e)  D.C.  Ammeters:  (i)  Input  A.(1)  Ranges and (number o f i n s t r u m e n t s ) :  5 A. (1) ; 15 A. (1) (f)  Shunts; (i)  Input  Ranges and (number o f each t y p e ) :  [50 mV. o u t p u t ]  1000 A . ( 2 ) ; 500 A . ( 1 ) ; 300 A . ( 3 ) ; 200 A . ( 1 ) ; 150 A . ( 2 ) ; 100 A . ( 4 ) ; 80 A . ( 5 ) ; 75 A . ( 1 ) ; 50 A. ( 9 ) ; 25 A . ( 1 ) ; 24 A . ( 1 ) ; 15 A. ( 1 ) ; 5 A . ( 3 ) ; 1.5 A . ( 2 ) . (g)  D.C.  Millivoltmeters;  (i)  Input  Ranges and (number o f i n s t r u m e n t s ) :  50 mV.. (ii)  Typical  (6) ; 50 mV. (2) ; 50 mV. (2)  Accuracy:  1/4 to 1/2 o f 1% F.S. (h)  D.C. V o l t m e t e r s : " (i)  Input  •  Ranges and (number o f i n s t r u m e n t s ) :  6000 V. ( 1 ) ; 300 V. ( 1 ) ; 150/300 V. ( 1 ) ; 15/150 V. ( 2 ) ; 10/20 V. ( 1 ) ; 3/15/150 V. ( 4 ) ; 1.5/15/150 V. (3)  (i)  Wattmeters: (i)  Input  Ranges and (number o f i n s t r u m e n t s ) :  7.5/15 KW.(5); 3/6/12 KW.(1); 1.5 KW. ( 1 ) ; 1.5/3/6 KW.(l); 1.0 KW. (1) ; . 750 KW. (2) ; .750 W. (1) ; 750 W. (3) ; 375/750/1500 W, (1) ; 150 W. ( 1 ) ; 100 W.(1); 37.5/75/150 W. (2) (ii)  Typical  Accuracy:  1/2 to 3/4 o f 1% F.S.  7  e l e c t r i c a l quantities on the additional machine, a transducer to measure torque should not be required f o r most of the undergraduate  experiments.  Since the actual measurement of mechanical power would be d e s i r a b l e , a t o r quemeter might eventually be added or the load angle transducer by the Power Group''" adapted for use with this system.  developed  Angular shaft v e l o c i t y  may be measured using a tachometer and voltage transducer. transducers to measure e l e c t r i c a l inputs are required.  Hence, only  Since power may  be  calculated from voltage and current inputs using the computer, transducers for voltage and current are a l l that are required.  For experiments using  two a.c. machines, as many as eleven voltage transducers and ten current transducers could be used (one d.c. c i r c u i t , three 3-phase c i r c u i t s , tachometer output).  and  However, a saving i n the number of transducers can be  r e a l i z e d by using only one a.c. machine i n two-motor experiments or by measuring only two of three phases i n two-a.c. machine experiments.  A minimum of s i x  current transducers and seven voltage transducers are required with this constraint.  Since only one undergraduate experiment involves the use of two  a.c.. machines, this l i m i t a t i o n appears to be j u s t i f i e d . A generalized block diagram f o r the laboratory computer system i s shown i n figure 2.1.  I t consists of s i x subsystems: a set of transducers,  an analog l i n k , an analog to d i g i t a l i n t e r f a c e , a d i g i t a l l i n k , a d i g i t a l computer, and an input/output device for user communication.  This diagram  i s generalized i n the sense that either the d i g i t a l or analog l i n k may  be  short i n length depending on the type and location of computer and the transmission scheme chosen.  Specifications for the input/output device, the main  transmission l i n k , the analog to d i g i t a l i n t e r f a c e , and the computer are studied i n the following sections.  Suitable devices are chosen i n each case  and a system for the e l e c t r i c a l machines laboratory i s  proposed.  I I I U U I III /c  inputs  , ANALOG  TRANSDUCER analog  SET  link  D/G/ M L  1 INTERFACE  digital  link  COMPUTER  timing  j INPUT/  data  buTPur  —p*—  DEVICEl  BLOCK DIAGRAM  OF  SYSTEM :  FIGURE  2.1 00  9  2.2  Input/Output  Device  An input/output device f o r user communication i s required f o r s e v e r a l purposes.  F i r s t of a l l , i t w i l l allow the experimenter  to i s s u e  commands to the computer to govern the data a c q u i s i t i o n and processing from the experiment. experiment  Secondly, i t w i l l permit the input of data concerning the  (e.g.: conversion u n i t s , transducer ranges, channel i n p u t s , e t c . ) .  F i n a l l y , i t w i l l be required f o r the output of r e s u l t s from the computer. The device required must be able to accept inputs from the user ( t y p i c a l l y alphanumeric minute).  characters at rates up to 120 f i v e - c h a r a c t e r words/  A l s o , i t must be able to produce outputs of a s i m i l a r nature,  p r e f e r a b l y making permanent copies of t h i s information. F i n a l l y , the device s e l e c t e d must be s u i t a b l e f o r use i n the e l e c t r i c a l machines l a b o r a t o r y environment. The most s u i t a b l e input/output device f o r t h i s p r o j e c t i s the standard KSR Model 33 t e l e t y p e . This device can be used to type i n or p r i n t out i n f o r m a t i o n at a r a t e of up to 10 characters/second.  Although a CRT  d i s p l a y device would have a f a s t e r output response and would allow the output of graphic information as w e l l , the t e l e t y p e was chosen on the b a s i s of cost.  2.3  Transmission Link The transmission l i n k i s required to transmit measurement data  from the e l e c t r i c a l machines laboratory to the computer.  Since the t r a n s -  ducers are required to produce data which i s accurate to ^1%, the transmission l i n k must be capable of conveying t h i s information without a s u b s t a n t i a l degradation i n accuracy.  A l s o , the transmission l i n k chosen must be able to  handle data from inputs up to 540 Hz.in frequency (since the transducers accept inputs up to the n i n t h harmonic of 60 Hz.). that the cost and complexity of the data l i n k be  F i n a l l y , i t i s important  minimized.  10  The  two  a l t e r n a t i v e s c o n s i d e r e d were analog, - and  The  p r i n c i p l e advantage of d i g i t a l  its  higher  to  immunity  implement d i g i t a l  t r a n s m i s s i o n over analog  to n o i s e i n t e r f e r e n c e .  transmission.  As w e l l , the use of  to d i g i t a l  d e s i r a b l e to use  existing f a c i l i t i e s . i5  interface.  electrical  to *10  V.F.S. was  analog  2.4  machines  analog  interfaces, i t  to take advantage of  transmission  e x p e c t e d to y i e l d  t h i s means o f t r a n s m i s s i o n was transmission  transmission  S i n c e analog  digital  S i n c e a l l the computers a v a i l a b l e  t h i s department f o r t h i s p r o j e c t a r e equipped w i t h  would be  transmission i s  However, the hardware r e q u i r e d  t r a n s m i s s i o n would r e q u i r e the d e s i g n of a d e d i c a t e d  in  transmission  t r a n s m i s s i o n i s g e n e r a l l y more c o s t l y and more complex  than t h a t r e q u i r e d f o r a n a l o g  l a b o r a t o r y analog  digital  these  at l e v e l s i n the o r d e r  adequate performance f o r our  s e l e c t e d f o r use  i n the  of  purposes,  laboratory/computer  link.  A n a l o g to D i g i t a l The  analog  Interface  to d i g i t a l  F i r s t o f a l l , i t must be  i n t e r f a c e must meet s e v e r a l  inputs  and  p r e f e r a b l y more w i t h p r o v i s i o n s f o r simultaneous sampling of a l l i n p u t s  (to  permit  a b l e to h a n d l e a t l e a s t  requirements.  t h i r t e e n analog  c a l c u l a t i o n of power and phase r e l a t i o n s h i p s ) .  a b l e to h a n d l e input, s i g n a l s up frequency.  to 540  Hz.  Secondly, i t must  ( n i n t h harmonic o f 60 Hz.)  Next, the q u a n t i z a t i o n e r r o r which adds to the t o t a l  of the measurement must be  an o r d e r o f magnitude l e s s than ^ 1 %  be  in  uncertainty  F.S.  Hence,  2 the d i g i t a l bits,  r e p r e s e n t a t i o n o f the i n p u t s h o u l d be  e r r o r i s * 1/2  10 b i t s y i e l d s The 2.3.  As  level in 2  = 512  levels  an e r r o r o f -1 p a r t i n 1024  at l e a s t 10 b i t s  (for 9  f o r u n i p o l a r i n p u t ; hence,  parts for a b i p o l a r input).  s p e c i f i c a t i o n s of the a v a i l a b l e i n t e r f a c e s are shown i n Table  these  s u i t a b l e choice  devices  are now  designed,  the h y b r i d  f o r t h i s p r o j e c t s i n c e o n l y i t has  i n t e r f a c e i s the individual  only  sample-and-hold  11  T a b l e 2.3:  INTERFACE  SPECIFICATIONS  Hybrid Interface  Sys terns Lab. Interface  1. M u l t i p l e x Channels  16  8  2. M u l t i p l e x Input L e v e l  ±100' Y. ±10 V.  ±5 V.  Parameter  ±1 V. 3. Sample and H o l d U n i t s 4. O p e r a t i n g  Frequency  5. A/D C o n v e r s i o n 6. A/D Word  Time  Length  7. A d d i t i o n a l  Features  1 p e r channel  3  20 KHz.  < 10 KHz,  20 ysec. 12 b i t s -Analog Computer -D/A C o n v e r t e r s -Sampling Frequency Control  10 b i t s -D/A  Converters  12  u n i t s and enough i n p u t m u l t i p l e x e r these f e a t u r e s ,  channels.  the systems l a b o r a t o r y  Upon m o d i f i c a t i o n  to i n c l u d e  i n t e r f a c e s f o r the PDP-8/L and NOVA  computers would be as s u i t a b l e as the h y b r i d i n t e r f a c e .  2.5  Computers The computer chosen f o r t h i s p r o j e c t must m e e t s e v e r a l F i r s t of a l l ,  to p e r m i t an a c c u r a t e i n one word.  t h e word l e n g t h  digital  representation  o f the i n p u t  be s u f f i c i e n t  d a t a t o be s t o r e d  F o r ± 1 % a c c u r a c y , a word l e n g t h o f a t l e a s t 7 b i t s  i s ±..1/2 l e v e l  i n 2^ l e v e l s f o r u n i p o l a r i n p u t )  S e c o n d l y , the memory r e q u i r e d the system must be e s t i m a t e d . and  o f the computer s h o u l d  requirements.  (max. e r r o r  i s required.  '  t o s t o r e the programs to o p e r a t e  A l t h o u g h i t i s f e a s i b l e to segment  s t o r e them on an e x t e r n a l s t o r a g e  device,  the programs  a t l e a s t a p o r t i o n o f the programs  must be s t o r e d i n the computer's memory a t any g i v e n  time.  An e x i s t i n g  3 implementation  o f s o f t w a r e f o r t h i s system d i v i d e s the s o f t w a r e i n t o  three  p o r t i o n s , one o f which o c c u p i e s a p p r o x i m a t e l y 6 K words o f memory.  This  i m p l e m e n t a t i o n was made u s i n g  Monitor  System S o f t w a r e .  the PDP-9 computer and i t s a s s o c i a t e d  I t may be p o s s i b l e to reduce the number o f program i n s t r u c t i o n s  by w r i t i n g a more s p e c i a l i z e d r o u t i n e s i n c e  the PDP-9 R e s i d e n t M o n i t o r o c c u p i e s  4 1635 words  o f memory a l o n e .  However, t h i s i s b a l a n c e d by the need f o r  a d d i t i o n a l s o f t w a r e to p e r m i t t i m e - s h a r i n g sets.  o r p o l l i n g o f the v a r i o u s  As w e l l , an a d d i t i o n a l s o f t w a r e segment w i l l be r e q u i r e d  a n a l y s i s and t r a n s i e n t a n a l y s i s . requires  time samples on the PDP-8/L computer.~* a computer w i t h a memory s u f f i c i e n t l y program i n s t r u c t i o n s .  f o r spectral  A t y p i c a l Fast F o u r i e r Transform  6400 words o f memory s t o r a g e  (both  data and program)  machine;  routine  to h a n d l e 2048  Hence, i t would be d e s i r a b l e t o s e l e c t l a r g e to h a n d l e a t l e a s t 6 K words o f  13  A third  c o n s i d e r a t i o n i s the amount o f d a t a to be s t o r e d i n memory.  An upper l i m i t on the amount of d a t a which i s produced may  be e s t i m a t e d by  c o n s i d e r i n g how  and s p e c t r a l a n a l y s i s . up  experiment  much i n f o r m a t i o n i s r e q u i r e d f o r t r a n s i e n t  S i n c e i n p u t waveforms w i l l  to the n i n t h harmonic o f 60 Hz.  from an  i n c l u d e frequency  and s i n c e i t i s d e s i r a b l e to  these waveforms f o r i n t e r v a l s o f time up  to one  second,  o f d a t a ( N y q u i s t r a t e sampling) w i l l be produced  components  observe  as many as 1080  p e r channel p e r  samples  second.  However, f o r s t e a d y - s t a t e measurements, much l e s s d a t a i s r e q u i r e d so t h a t a l a r g e d a t a s t o r a g e requirement  may  not be j u s t i f i e d .  p o s s i b l e to b u f f e r the d a t a i n the computer and output  As w e l l , i t may i t v i a the d a t a  to an e x t e r n a l b u l k s t o r a g e d e v i c e between i n p u t samples.  such  be transfer  Thus, a memory o f  8 K words o r l a r g e r i s recommended. Other  f a c t o r s governing  the d e c i s i o n of computer are speed, b u l k  s t o r a g e c a p a c i t y , e x i s t e n c e o f d a t a a c q u i s i t i o n s o f t w a r e , and of h i g h - l e v e l languages The  and  compilers.  computers a v a i l a b l e were the DEC  the DATA GENERAL NOVA.  The  specifications  the l a b o r a t o r y , the PDP-9 was  important  PDP-9, the DEC  PDP-8/L,  are compared i n T a b l e 2.4.  the PDP-8/L and NOVA computers are p o r t a b l e and  magnetic tape  availability  Although  c o u l d be used d i r e c t l y i n  s e l e c t e d because o f i t s 16 K word memory, i t s  t r a n s p o r t s , and i t s e x i s t i n g d a t a a c q u i s i t i o n s o f t w a r e .  factor i n this  and  c h o i c e was  the a v a i l a b i l i t y o f a s u i t a b l e  An  analog  interface. 2.6  F i n a l System C o n f i g u r a t i o n The  system s p e c i f i e d uses a PDP-9 computer, the h y b r i d i n t e r f a c e ,  a m u l t i - w i r e -10  V.F.S. a n a l o g  t r a n s m i s s i o n l i n k , a s t a n d a r d KSR  Model  33  t e l e t y p e , and a t h i r t e e n to s i x t e e n i n p u t t r a n s d u c e r s e t (to be d i s c u s s e d i n Chapter  3).  14  TABLE 2.4:  Parameters  COMPUTER SPECIFICATIONS  PDP-9  NOVA  PDP-8/L  16 K words  4 K words  4 K words  2. Word L e n g t h  18 b i t s  12 b i t s  16 b i t s  3. C y c l e Time  1 ysec.  1.6 u s e c .  2.6 u s e c .  4. Add Time  2 usee.  3.2 y s e c .  5.9 y s e c .  5. P e r i p h e r a l s  -Teletype -Display -Hybrid I n t e r face -Magnetic Tape Drives -Paper Tape  -Teletype -Paper Tape -Analog I n t e r face  -Teletype -Paper Tape -Analog I n t e r f a c e  1. Memory  size  6. B u l k S t o r a g e Capacity 7. F e a t u r e s  160 K words - D i r e c t Memory Access -Data Channel -Program I n t e r r u p t -Extended A r i t h m e t i c Element -Monitor Software System  -Data  Channel  -Program rupt  Inter-  -4 Accumulators -Data  Channel  -Program Interrupt  15  . The system c o n f i g u r a t i o n s p e c i f i e d i s by no means a b s o l u t e . ually, on  Event-  i t might be d e s i r a b l e to use t h e PDP-8/L o r NOVA because o f the demands  the PDP-9 computer.  s i g n a l transmission  The ± 1 0 V . F . S . . a n a l o g o u t p u t s o f t h e t r a n s d u c e r s f o r  to t h e h y b r i d  i n t e r f a c e can e a s i l y be m o d i f i e d  V.F.S. l e v e l s u i t a b l e f o r use w i t h the PDP-8/L and NOVA i n t e r f a c e s . use o f the PDP-8/L o r NOVA computers w i l l  However,  r e q u i r e a d d i t i o n a l hardware such  as an a d d i t i o n a l 4 K o f memory, a b u l k s t o r a g e m o d i f i c a t i o n o f t h e systems  to a ±5  device  such as a d i s c , and  l a b o r a t o r y i n t e r f a c e to h a n d l e a t l e a s t t h i r t e e n  channels o f i n p u t w i t h simultaneous sampling o f a l l channels u s i n g i n d i v i d u a l sample-and-hold d e v i c e s . transmission serious  As w e l l , a s p e c i a l l a b o r a t o r y  l i n k c o u l d be added s h o u l d  problem.  noise  i n t e r f a c e and d i g i t a l .  i n t e r f e r e n c e prove to be a  16  3. 3.1  Proposed  TRANSDUCERS  Specifications  The f o l l o w i n g s p e c i f i c a t i o n s a r e proposed as g u i d e l i n e s f o r the d e s i g n o f the t r a n s d u c e r s .  The t r a n s d u c e r s e t w i l l  c o n s i s t o f 13 to. 16 u n i t s  w i t h a t l e a s t 6 c u r r e n t t r a n s d u c e r s and 7 v o l t a g e t r a n s d u c e r s .  Both  types  o f t r a n s d u c e r s must be a b l e t o o p e r a t e w i t h i n p u t s w i t h f r e q u e n c i e s up t o 540 Hz. w i t h ar> a c c u r a c y b e t t e r than ^ 1 % F.S. operate  They must a l s o be a b l e to  over a t y p i c a l i n d o o r temperature range o f 21° * 10°C.  t r a n s d u c e r s must be a b l e to h a n d l e c u r r e n t observed  c u r r e n t s up to 50 amperes, the l a r g e s t  on the machine s e t s (see T a b l e 2.1).  o f t h e c u r r e n t t r a n s d u c e r s must p e r m i t a t v o l t a g e s as h i g h as 500 v o l t s  As w e l l ,  the d e s i g n  c u r r e n t measurement i n conductors  abbve ground.  The v o l t a g e t r a n s d u c e r s must  be a b l e to measure v o l t a g e s up to 500 v o l t s w i t h 500 v o l t s  The c u r r e n t  common-mode v o l t a g e s up to  ( l a r g e s t s t e a d y - s t a t e v o l t a g e a n t i c i p a t e d was a p p r o x i m a t e l y 150%  o f t h e peak v a l u e o f r a t e d machine output  v o l t a g e , i . e . : 1.5 x  x 208 V.).  A number o f i n p u t ranges s h o u l d be p r o v i d e d w i t h each t r a n s d u c e r t o p e r m i t a c c u r a t e measurements a t lower  input l e v e l s .  Finally,  t r a n s d u c e r s must a l l o w the c o n v e n t i o n a l i n s t r u m e n t s  3.2  Transducer  this  design.  to be connected  normally.  Design  Six current transducers in  the d e s i g n o f t h e  and t e n v o l t a g e t r a n s d u c e r s were p r o v i d e d  Though o n l y s i x c u r r e n t t r a n s d u c e r s and seven v o l t a g e t r a n s -  ducers were r e q u i r e d , t h r e e a d d i t i o n a l v o l t a g e t r a n s d u c e r s were i n c l u d e d because o f the a v a i l a b i l i t y o f 16 m u l t i p l e x e r channels of the voltage  transducers.  and the low c o s t  17  3.2.1.  Current  Transducers  A H a l l M u l t i p l i e r was design  chosen f o r use  used i n c o r p o r a t e s a c o n s t a n t - c u r r e n t  the H a l l m u l t i p l i e r ,  and  to the computer.  shown i n f i g u r e  3.1.  devices,  H a l l m u l t i p l i e r was  were c o n s i d e r e d  Current  a number o f i n p u t c u r r e n t  3.2.1.1  Hall  constant,  to be measured, i ^ ,  design with  flows  i t s availability in  through the w i n d i n g  o f the H a l l - E f f e c t and  to be  to Ki„, where K i s a f  amperes and  i n p u t ranges, 0-3  0-20  s e t up i n the a i r  d e v i c e , v^,  i s equal  A list  i n the d e s i g n i s p r e s e n t e d  to  If i ^ is  constant,  Six current  amperes, and  amperes and  the s i x c u r r e n t i n p u t s a l l o w e d .  encircling  i ^ i s the e x c i t a t i o n c u r r e n t .  s e v e r a l i n p u t c u r r e n t ranges.  i n p u t ranges, 0-40  liers utilized  and  d i f f e r e n t m u l t i p l i e r s were used i n the c u r r e n t  to p r o v i d e  ducers w i t h  output  a p r o p o r t i o n a l magnetic f i e l d  i s a constant,  v, i s equal h Two  cost, r e s p e c t i v e l y .  ranges.  v o l t a g e a t the output  K ^ i ^ i ^ , where  devices  diagram o f a H a l l - E f f e c t m u l t i p l i e r i s shown i n f i g u r e  the i r o n core c a u s i n g The  magneto-  Multiplier  A simple The. c u r r e n t  and  other  chosen o v e r s e r i e s r e s i s t a n c e p r i m a r i l y because o f  e l e c t r i c a l i s o l a t i o n between i n p u t and  gap.  a number o f  and m a g n e t o r e s t r i c t i v e c u t o f f and h i g h  signal  configuration i s -  selected i n preference-to  transformers  The  excitation for  the output  A b l o c k diagram of t h i s  u n s u i t a b l e because of d.c.  The H a l l m u l t i p l i e r was  3.2.  to p r o v i d e  i n c l u d i n g s e r i e s r e s i s t a n c e s , current transformers,  r e s t r i c t i v e devices.  its  source  a d i f f e r e n t i a l a m p l i f i e r to b o o s t  for transmission  The  as a c u r r e n t t r a n s d u c e r .  0-1.5  transducer transducers  s i x current  trans-  amperes, are p r o v i d e d  of s p e c i f i c a t i o n s o f the H a l l i n Table  3.1.  for multip-  18  0 CURRENT TRANSDUCER CONFIGURATION: FIGURE  3.1  19  Table  3.1:  HALL MULTIPLIER SPECIFICATIONS (BELL INC.)  Model No. HM-3500 ( f o r p a r a l l e l connected  Parameter A.  Magnetic F i e l d  D.  Hall  1 mft. 0.39%/°C. 20 mft/KHz. 40 A." , < 1 KHz.  0.06ft. 0.39%/°C. 4 ft/KHz. 3 A. < 1 KHz.  20 fi  2.5 -ft. < +.15%/°C. < 25% o f R i n 330 mA. <L 500 KHz.  Input  R e s i s t a n c e ( i f = 0) Temp. C o e f f . o f above Magnetoresistance Current Rating Frequency Range C.  Model No. HM-3010 coils)  Input  Resistance Temp. C o e f f . o f above Reactance Current Rating Frequency Range Hall  field  < +..02%/°C. < +2.5% o f R i n 330 mA. < 100 KHz.  Output  Resistance Load R e s i s t a n c e Maximum Output Temp. C o e f f . o f V j  io fi. 50 fi. 200 mV.  10 fi. 50 ft. 200 mV.  0°C.to 50°C. -25°C. t o 75°C.  <; ± . 5 % < ±1%  < ±.5% < ±1%  < .5% F.S. < .5% F.S. 3.°/KHz. -.3 dB./KHz. < .2 mV./KHz.  < .5% F.S. < .5% F.S. 3P/KHz. -.3 dB7KHz. < .1 mV./KHz.  < .25% F.S. < .3 mV;. < .3 mV. d.c.  < .25% F, < .1 mV. < 12 mV. d.c.  Hall  Output v s . F i e l d  Input  L i n e a r i t y E r r o r (ij=K) Remanent R e s i d u a l Phase S h i f t Frequency Response Inductive Error Voltage H a l l Output v s . H a l l  Input  L i n e a r i t y E r r o r (if=K) R e s i s t i v e Error Voltage Thermal E r r o r V o l t a g e  20  3.2.1.2  Constant-Current  A constant-current and  a current regulator.  Source source was implemented u s i n g a v o l t a g e  Both discrete-component  source  "voltage/current  cross-  6 over  supplies  and i n t e g r a t e d - c i r c u i t r e g u l a t o r s were c o n s i d e r e d  as c u r r e n t r e g u l a t o r s . 3.3,  were c o n s i d e r e d  f o r use  S e v e r a l p o s s i b l e c o n f i g u r a t i o n s , as shown i n f i g u r e  for supplying  e x c i t a t i o n current  to t h e 12 H a l l m u l t i p l i e r s  In f i g u r e 3 . 3 ( i ) and 3 . 3 ( H ) , one main discrete-component r e g u l a t o r i s used while  i n f i g u r e 3 . 3 ( i i i ) i n d i v i d u a l i n t e g r a t e d - c i r c u i t r e g u l a t o r s a r e used.  Configuration  3.3(i)  i s s u p e r i o r t o 3 . 3 ( i i ) and 3 . 3 ( i i i ) f o r c u r r e n t  a t i o n ; however, a f a i r l y voltage  drop a c r o s s  l a r g e c u r r e n t r e g u l a t o r i s needed t o m a i n t a i n t h e  t h e m u l t i p l i e r s (approx. 50 v o l t s @ 300 mA.) .  of lower c o s t , i t was d e c i d e d 3.3(  regul-  On t h e b a s i s  t o use i n d i v i d u a l r e g u l a t o r s as shown i n f i g u r e  iii). The  design  c h i l d UA723C v o l t a g e  o f t h e i n d i v i d u a l r e g u l a t o r s was s t r a i g h t f o r w a r d . r e g u l a t o r s were used i n t h e c i r c u i t  to r e g u l a t e t h e v o l t a g e  drop a c r o s s  a current-sensing  s p e c i f i c a t i o n s o f t h e yA723C r e g u l a t o r a r e l i s t e d handling  Fair-  shown i n f i g u r e 3.4  resistance.  i n Table  3.2.  The The c u r r e n t - ,  c a p a b i l i t i e s of t h e r e g u l a t o r s were extended by u s i n g power t r a n s i s t o r s  at t h e o u t p u t s .  This design  provides  a measured c u r r e n t r e g u l a t i o n o f 0.05%  f o r l o a d v a r i a t i o n s (0£L to 20ft.) under t y p i c a l l a b o r a t o r y 3.2.1.3  conditions.  Level Amplifier  A . l e v e l amplifier i s required  t o b o o s t the ±200 mV.F.S. output o f  each H a l l m u l t i p l i e r up to t h e ± 1 0 V.F.S. t r a n s m i s s i o n H a l l - E f f e c t d e v i c e has a common-mode v o l t a g e to t h e v o l t a g e  level.  Since the  superimposed on i t s output due  drop i n t h e r e s i s t i v e semiconductor m a t e r i a l from t h e 300 mA.  excitation current, a d i f f e r e n t i a l amplifier i s required.  This amplifier  must have a d i f f e r e n t i a l g a i n o f 50 and a common-mode r e j e c t i o n r a t i o  better  21  Current  Ic  Regulator  Hall Multiplier  CM  Current Regulator  66  O  (it)  (.tu)  CURRENT REGULATOR CONFIGURATIONS : FIGURE 3.3  i  R,  Rp (current sensing resistance)  R.  R  L  CURRENT  (LOAD)  REGULATOR: FIGURE 3.4  2000-3000JT.  49.911  200 mv.  ma.%.  49.9J7.  DIFFERENTIAL AMPLIFIER DESIGN FIGURE 35  23  T a b l e 3.2:  Max.  s u p p l y = 1 2 V. t o 15 V. s u p p l y = 1 2 V. to 40 V. s u p p l y = 1 2 V- to 15 V. (0° < T A <70° C)  0.01 0.1  0.1 0.5 0.3  %V out %V out %V  Load C u r r e n t = l to 50 mA. Load C u r r e n t = l to 50 mA." (0 < T < 70°C)  0.03  0.2 0.6  Pout ^ out  f=50 Hz. t o 10 KHz. f=50 Hz. to 10 KHz.  74 86  ' Condition V  Min.  V  v  Load R e g u l a t i o n  Unit  Typ.  Parameter Line Regulation  SPECIFICATIONS OF FAIRCHILD yA723C  Out  v  A  Ripple Rejection Average Temp. C o e f f . of V  0 £ T  A  0.003  < 70°C.  dB. dB. 0.015  %/°C.  0  Reference  Voltage  6.80  7.15  7.50  %/1000 h r s ,  0.1  Long Term S t a b i l i t y ^  V".  Input V o l t a g e Range  9.5  40  V.  Output V o l t a g e Range  2.0  37  v'.  Input-Output Voltage D i f f e r e n t i a l  3.0  38  V ..  ABSOLUTE MAXIMUM RATINGS  Input-Output D i f f e r e n c e V o l t a g e Maximum Output C u r r e n t I n t e r n a l Power D i s s i p a t i o n O p e r a t i n g Temperature Range C u r r e n t from V,,™  40 V. 150 m A . 800 mW. 0°C to 70°C. 15 mA. ,  24  than 250:1.  Finally,  the output  impedance of the a m p l i f i e r s h o u l d be as  low as p o s s i b l e to f a c i l i t a t e p r o p e r The a m p l i f i e r d e s i g n e d  signal transmission.  f o r t h i s purpose i s shown i n f i g u r e  3.5,  u s i n g a M o t o r o l a MC1741CG o p e r a t i o n a l a m p l i f i e r w i t h s p e c i f i c a t i o n s as listed  i n T a b l e 3.3.  marized  3.2.2  The d e t a i l s of the d e s i g n of t h i s a m p l i f i e r a r e sum-  i n APPENDIX A.  V o l t a g e Transducers  N  A v o l t a g e d i v i d e r f o l l o w e d by a u n i t y - g a i n b u f f e r a m p l i f i e r as shown i n f i g u r e 3.6 were used i n the d e s i g n of the v o l t a g e t r a n s d u c e r .  This  arrangement a l l o w s the r e d u c t i o n of the ±500 V.F.S. l a b o r a t o r y i n p u t s to the i l O V.F.S. t r a n s m i s s i o n l e v e l s .  To p e r m i t v o l t a g e measurements w i t h  r e s p e c t t o an ungrounded r e f e r e n c e , a b a l a n c e d d i v i d e r and d i f f e r e n t i a l a m p l i f i e r were used. were p r o v i d e d . i n APPENDIX B.  Two measurement ranges,  0-500 v o l t s and 0-10  volts,  The d e t a i l s of the d e s i g n o f these t r a n s d u c e r s a r e summarized  25  TABLE 3.3:  SPECIFICATIONS OF MOTOROLA MC1741CG  Condition  Parameter Input O f f s e t  Voltage  Input O f f s e t  Current  R  Min.  < 10 K ft.  Input B i a s C u r r e n t Input  0.3  Resistance > 2Kft.,  Large S i g n a l Voltage Gain Swing  ^  Supply  Voltage  Units  2.0  6.0  mV.  30.  200.  - nA.  200.  500.  nA.  1.0 100,000  ±12  ±14  V.  R^ > 2 Kft.  ±10  ±13  V.  ±12  ±13  V.  70  90  =  1  0  V  Input V o l t a g e Range CMRR  Max.  0UT P^ > 10 Kft.  V  Output V o l t a g e  20,000  Typ.  R  < 10 Kft.  R  < 10 Kft.  30  dB. 150 yV./V.  Rejection Ratio 50  Power Consumption T r a n s i e n t Response ( u n i t y gain)  85 mW.  V „ = 20 mV. IN T  R^ = 2 Kft.; C  < 100 pf.  -risetime  0.3  ysec.  -overshoot  5.0  %  Slew Rate ( u n i t y  > 2 Kft.  gain)  * The f o l l o w i n g a p p l y f o r Input O f f s e t  Voltage  Input O f f s e t  Current  0.5  0°C < T < 70°C. A R  g  ^ 10 Kft.  Input B i a s C u r r e n t Large S i g n a l Voltage Gain Output V o l t a g e  Swing  V. /ysec.  > 2 Kft. = ±10 V, OUT R > 2 Kft.  15,000  V  +10  7.5  mV.  300.  nA.  800.  nA.  —0 4  2K-Q.  (vA-Ve,!^  Zoo*  VOLTAGE TRANSDUCER DESIGN: FIGURE ' 3.6  27  4.  RESULTS  Two s e r i e s o f measurements were made on the t r a n s d u c e r s e t to determine  4.1  i t s performance.  First  S e t o f Measurements The f i r s t  s e t was conducted  Measurements were made to determine:  on the t r a n s d u c e r s e t by i t s e l f .  (1) measurement e r r o r ,  (3) common-mode r e j e c t i o n r a t i o , and (4) f r e q u e n c y r e s p o n s e . of are  t h e t e s t s performed  i s included  i n APPENDIX C.  (2) o f f s e t  drift,  A description  The r e s u l t s o f these  tests  p r e s e n t e d i n T a b l e 4.1. To b e g i n w i t h , t h e performance  of the c u r r e n t t r a n s d u c e r s under  t y p i c a l l a b o r a t o r y c o n d i t i o n s was checked.  The l a r g e s t magnitude of measure-  ment e r r o r observed was 0.82% F.S. f o r b o t h t h e 0-40 and 0-3 ampere i n p u t ranges. found  The t y p i c a l o u t p u t o f f s e t d r i f t  over a p e r i o d of t h r e e hours was  t o be 0.12% F.S. f o r a l l i n p u t ranges.  Finally,  the t y p i c a l  frequency  c u t o f f was measured to be a p p r o x i m a t e l y 30 K H z . ( f o r the 0-3 ampere i n p u t range) . A s i m i l a r s e t of measurements was made on t h e v o l t a g e t r a n s d u c e r s to  check  t h e i r performance.  F o r t h e 0-500 v o l t  measurement e r r o r observed was 0.39% F.S.  i n p u t range,  The output o f f s e t d r i f t  case was n e g l i g i b l e f o r a three-hour measurement p e r i o d . mode r e j e c t i o n r a t i o was 104:1.  As w e l l ,  common-  Though t h e 0-500 v o l t i n p u t  range was found t o perform a d e q u a t e l y , the 0-10 v o l t t h e 2:1 v o l t a g e d i v i d e r used  p r o v i d e f o r l a r g e common-mode v o l t a g e s .  The worst  i n this  t h e f r e q u e n c y response was f l a t  to w i t h i n ± 3 dB. up t o a f r e q u e n c y of 40 KHz.  s a t i s f a c t o r y because  the l a r g e s t  i n p u t range was un-  i n the d e s i g n d i d n o t  T a b l e 4.1:  tf , Transducer y  Voltage (0-500 V.)  Current (0-40A.)  Current (0-3A)  Max. D.C. Measurement E r r o r (%F.S.)  0.39  MEASURED TRANSDUCER  Typ. A.C. Measurement E r r o r (%F.S.)  0.66  CHARACTERISTICS  Output Offset D r i f t %F.S./3 h r s .  negligible  -  0.82  0.63  ~  0.115  0.114  CMRR @D.C.  104:1  29  4.2  Second Set of Measurements To evaluate the design more f u l l y , a system s i m i l a r to the  proposed for the e l e c t r i c a l machines laboratory was was  set up.  one  This system  implemented i n the hybrid computer laboratory using the PDP-9 computer,  the hybrid i n t e r f a c e , and the transducer set developed. measured using d.c. inputs only.  System errors were  A f u l l description of the tests conducted  i s included i n Appendix C. The worst measurement errors were found to be 2.2% current inputs and 1.4%  F.S.  for the voltage inputs.  what larger than a n t i c i p a t e d . o f f s e t voltage i n the analog  for the  These values are some-  The main source of error appears to be  to d i g i t a l i n t e r f a c e .  the  At the time of measure-  ment, the input o f f s e t voltage on the hybrid i n t e r f a c e was (2£70 mV.).  F.S.  rather large  Subsequent measurements show that the normal input o f f s e t  voltage i s of the order of 20 mV.  Hence, better r e s u l t s may  with this system than were obtained i n this test.  be expected  As w e l l , i t should  f e a s i b l e to reduce the o v e r a l l error even more by compensating for the o f f s e t voltage either with hardware or  software.  be  30 5.  CONCLUSIONS AND SUGGESTIONS  A set of transducers f o r measuring current and voltage waveforms on an e l e c t r i c a l machine set was designed, constructed, and tested.  The  r e s u l t s of t h i s design have been presented and i t i s concluded that the hardware developed i s u s e f u l as a part of a data a c q u i s i t i o n and processing system f o r the e l e c t r i c a l machines l a b o r a t o r y . A complete system i s proposed for use w i t h the transducers developed. system.  P a r t i a l t e s t s were made on t h i s  The r e s u l t s i n d i c a t e that the system design proposed i s workable. Future development of t h i s equipment w i l l r e q u i r e a d d i t i o n a l  hardware and software before p r a c t i c a l computer-assisted l a b o r a t o r y i n s t r u c t i o n can commence. For hardware, i t i s recommended that a d d i t i o n a l ranges f o r input to the transducers be provided.  In p a r t i c u l a r , the a d d i t i o n of lower voltage  ranges to the voltage transducer w i l l r e q u i r e an improved d i f f e r e n t i a l l e v e l a m p l i f i e r such as shown i n f i g u r e 5.1.  As w e l l , transducers to measure  shaft angle, v e l o c i t y , and torque might be added.  Overload p r o t e c t i o n for  the current transducers must be i n v e s t i g a t e d . Though the voltage t r a n s ducers may be e a s i l y protected using back-to-back  zener diodes at the inputs  of the o p e r a t i o n a l a m p l i f i e r s , i n t e r r u p t i o n of an overcurrent i s more d i f ficult.  The use of f a s t - a c t i n g fuses designed f o r SCR p r o t e c t i o n i s a  possible solution.  In a d d i t i o n , low-pass f i l t e r s w i t h lower c u t o f f frequencies  than the ones now being used on the transducer inputs may be r e q u i r e d .  If  the transducers are to be used w i t h a PDP-8/L or NOVA computer, hardware such as an a d d i t i o n a l 4K of memory, an e x t e r n a l bulk storage device such as a d i s c , and m o d i f i c a t i o n s to the m u l t i p l e x e r on the analog i n t e r f a c e to handle 16 channels w i t h i n d i v i d u a l sample-and-hold u n i t s w i l l be d e s i r a b l e . A l t e r n a t i v e l y , use of the PDP-9 computer w i l l r e q u i r e the i n s t a l l a t i o n of 16 lines.  31  A  SUPERIOR DIFFERENTIAL AMPLIFIER : FIGURE 5.1 :  c  32  from t h e e l e c t r i c a l machines l a b o r a t o r y t o the h y b r i d Eventually, graphical  computer  laboratory.  a d i s p l a y or x-y p l o t t e r would be u s e f u l f o r the d i s p l a y of  information. To p r o v i d e  is essential.  a u s e f u l working system, an e f f i c i e n t  s o f t w a r e package  Software i s a v a i l a b l e f o r data a c q u i s i t i o n and p r o c e s s i n g 3 7  using  t h e h y b r i d i n t e r f a c e and PDP-9.  '  However, a d d i t i o n a l s o f t w a r e w i l l  be r e q u i r e d , even i f these r o u t i n e s can be used, to c a l c u l a t e the p r o p e r values  required  may be r e q u i r e d the v a r i o u s  f o r the experiment.  Eventually, a dedicated  to permit time-sharing  r o u t i n e s i n the proper  executive  routine  of a number o f machines and to sequence  order.  33  '  APPENDIX  A  CURRENT TRANSDUCER AMPLIFIER DESIGN The  output v o l t a g e ,  e^, from a d i f f e r e n t i a l a m p l i f i e r o f t h e  9 c o n f i g u r a t i o n shown i n f i g u r e 3.5 i s  R • s where R^ i s the feedback r e s i s t a n c e , R is  the i n p u t d i f f e r e n t i a l v o l t a g e .  i s t h e i n p u t r e s i s t a n c e , and -^ e  g  For t h i s design, Rf/R  w  a  s  s  e  t  a  2  _e  50  t  g  to b o o s t the 1200 mV.F.S. output from t h e H a l l m u l t i p l i e r up t o ±10 V.F.S. Several non-ideal considered  to avoid  aspects  errors.  First  of t h e o p e r a t i o n a l a m p l i f i e r must be of a l l ,  may e x i s t due to the i n p u t o f f s e t v o l t a g e , the i n p u t b i a s c u r r e n t . current e f f e c t s w i l l  an o f f s e t  the i n p u t o f f s e t  I f a balanced c i r c u i t  tend  i n the output  t o c a n c e l each o t h e r  voltage  c u r r e n t , and  i s used, t h e i n p u t  bias  out so t h a t the output o f f -  9 set voltage  i s essentially AV = [1 + R./R ] V + R.I OUT f s os f os m i r r  where V To  OS  i s the i n p u t o f f s e t v o l t a g e  reduce AV^^, R  attenuate  g  i s the i n p u t o f f s e t  low v a l u e ,  r  0.306 v o l t s .  AV  '  F.S.).  25°C,  AV^ OUT max. TirT1  T h i s v o l t a g e may be n u l l e d u s i n g the  should  n o t exceed  Over the temperature  0.383  volts.  Hence, the  OUT max.  n e t maximum o f f s e t v o l t a g e ( e r r o r = 0.76%  At  J  f e a t u r e o f the o p e r a t i o n a l a m p l i f i e r .  0° t o 70°C,  current.  49.9ft., which does n o t  the H a l l m u l t i p l i e r output s u b s t a n t i a l l y .  was c a l c u l a t e d to be  range, °  OS  was s e t a t a f a i r l y  r  zero n u l l  and I  after nulling  i s approximately  0.076  volts  Though t h i s c a l c u l a t i o n i s r a t h e r c r u d e , the a c t u a l  i m p l e m e n t a t i o n has v e r i f i e d  t h a t the o f f s e t v o l t a g e  i s not a serious  problem.  34  Since  the H a l l  multiplier  i s r e s i s t i v e i n nature, the excitation  c u r r e n t g e n e r a t e s a common-mode v o l t a g e o f a p p r o x i m a t e l y 0.5 v o l t s output terminals.  To c h e c k t h e e r r o r  common-mode r e j e c t i o n The o v e r a l l  d u e t o t h e common-mode v o l t a g e , t h e  r a t i o of the d i f f e r e n t i a l amplifier  common-mode r e j e c t i o n  at the  ratio  must be c o n s i d e r e d .  f o r t h e r e s i s t i v e network and  g operational amplifier  c o n f i g u r a t i o n of f i g u r e  CMRR  t  CMRR  w h e r e t h e common-mode r e j e c t i o n  c  + c  CMRR  op amp  r a t i o o f t h e r e s i s t i v e network i s g i v e n by 1 +  CMRR  3.5 i s  =  R  .  /R  -  4a where a r e p r e s e n t s  t h e maximum f r a c t i o n a l  1% t o l e r a n c e r e s i s t o r s , imately  1275 y i e l d i n g  common-mode r e j e c t i o n  an output e r r o r  temperature c o e f f i c i e n t variations  the overall  deviation i n resistance.  specification  ratio  i s approx-  o f a p p r o x i m a t e l y 0 . 1 9 6 % F.S. o f -50 ppm./°C. l i m i t s  t o ± 0 . 2 5 % f r o m 0° t o 50°C. w h i c h i s m o r e t h a n  Using  A  resistance  adequate.  35  APPENDIX  B  VOLTAGE TRANSDUCER AMPLIFIER  The  d e s i g n of t h i s a m p l i f i e r  current transducers.  DESIGN  i s s i m i l a r to t h a t used f o r the  The c i r c u i t d e s i g n e d  i s shown i n f i g u r e  T h i s c i r c u i t may be a n a l y z e d by t a k i n g the T h e v e n i n circuit  a t the output  of the r e s i s t i v e d i v i d e r .  3.6. equivalent  The e q u i v a l e n t c i r c u i t i s  b a l a n c e d w i t h an e q u i v a l e n t v o l t a g e source of v a l u e  ^s R  and  +  s  (V. - V_) A B  h  volts  two e q u i v a l e n t r e s i s t a n c e s of v a l u e R R_ s B R  + R^ s  T h i s reduces  n_  B.  the r e s i s t i v e network to the s t a n d a r d d i f f e r e n t i a l  form as i n f i g u r e 3.5.  amplifier  The output v o l t a g e i s e q u a l to  , - "'\ <Y- V • A v a l u e of R^/R^ e q u a l to 1/50 was chosen f o r t h i s d e s i g n . i n p u t r e s i s t a n c e o f s e v e r a l thousand ohms, R R^ t o be 2 Kfi. were used f o r  To d i s s i p a t e the power l o s s ,  for this  was chosen to be 100 Kft. and 7 watt p r e c i s i o n power  resistors  V  S i n c e R^/R^ amplified.  To p r o v i d e an  i s c l o s e to u n i t y , the i n p u t o f f s e t v o l t a g e i s not  A n e t maximum output  design.  o f f s e t e r r o r of 0.08% F.S. was  calculated  36  The output e r r o r due to common-mode v o l t a g e s a t the i n p u t i s a s e r i o u s problem. mode r e j e c t i o n  F o r a 500 v o l t  common-mode v o l t a g e , an o v e r a l l  r a t i o o f 100 i s r e q u i r e d to l i m i t  these v o l t a g e s t o 1% F.S.-  common-  t h e output e r r o r due to  S i n c e the o v e r a l l CMRR i s a p p r o x i m a t e l y  1  equal to  R,/R'  + 4a  a must not exceed specified were used.  0.005.  f o r this design.  Hence, r e s i s t a n c e s w i t h a t o l e r a n c e of ± 0 . 5 % were Also r e s i s t o r  temperature  coefficients  of ± 5 0 ppm./°C.  37  APPENDIX  C  DESCRIPTION OF TESTS C l  Transducers C.l.l  Only  Measurement E r r o r The  c o n f i g u r a t i o n shown i n f i g u r e C l was used  i n p u t / o u t p u t c h a r a c t e r i s t i c s of the t r a n s d u c e r s .  to measure the  Inputs were a p p l i e d and  measured and from t h i s the c o r r e c t o u t p u t s were c a l c u l a t e d based desired  transducer r a t i o .  Next, the a c t u a l o u t p u t s were measured and the  d i f f e r e n c e s between the a c t u a l and c a l c u l a t e d o u t p u t s were used the measurement e r r o r s . the l i n e a r i t y the  on the  to compute  T h i s measurement a l s o g i v e s some i n d i c a t i o n of  of the t r a n s d u c e r s s i n c e a number of i n p u t s were used i n  tests. Measuring Equipment: D.C. V o l t a g e Source:  H e a t h k i t 0-400 V.D..C. r e g . s u p p l y  D.C. C u r r e n t Source:  Lambda 1-4 V.D.C  r e g . s u p p l y and p r e c i s i o n  resistances A.C  V o l t a g e Source:  Dropping  a.c. l i n e  Resistances:  Voltmeter:  (120 V.(r.m.s!)@ 60 Hz)  p r e c i s i o n 1(1-.0012) ft.  .:i(l+.0013) ft. .05(1+.0014) ft. F l u k e 4^/2 d i g i t D i g i t a l V o l t m e t e r accuracy: s p e c i f i e d to be <.05% F. S. measured to be 1. .10% F.S.  Measurement C o n d i t i o n s : -bench  environment  -approx.  70°F.  temperature  -1 hour warm-up p e r i o d Inputs Used: D.C:  420,300,200,100,50,0  A.C :  120 V. (r.m.s.)  volts  voltmeter —a  voltage source  -o-a-  voltage transducer  V ) volt me ter  precision current sensing resistance^ . voltage source  current » « limiter voltmeier (/  V j voltmeter  J  FIGURE  C.I: MEASUREMENT ERROR TEST  transducer  ciirrent transducer  FIGURE  voltmeter  {V)voltmeter  C.2: OFFSET  DRIFT TEST  V) voltmeter vol tage source  ©© }  vol (meter  FIGURE C.3: CMRR MEASUREMENT  39  C.1.2  Offset D r i f t With no i n p u t s , the output  v o l t a g e was monitored f o r a p e r i o d  of  approximately  in  f i g u r e C.2). The measurement c o n d i t i o n s were the same as i n C . l . l .  C.1.3  t h r e e hours u s i n g the FLUKE d i g i t a l v o l t m e t e r  Common-Mode R e j e c t i o n R a t i o In t h i s case,  t e s t i n p u t s o f 250 v o l t s d.c. and 120 v o l t s a . c .  (60 Hz.) were used as shown i n f i g u r e C.3. of  (as shown  t h e v o l t a g e t r a n s d u c e r s was computed.  From t h i s , t h e common-mode g a i n  The common-mode r e j e c t i o n  ratio  was c a l c u l a t e d u s i n g G CMRR =  assuming G^ e q u a l to 1/50.  — cm  ,  I n t h i s s e t of measurements, the FLUKE d i g i t a l  v o l t m e t e r was used t o measure the v a r i o u s v o l t a g e s and the t e s t  conditions  were i d e n t i c a l to those of C . l . l .  C.1.4  Frequency Response Inputs  illustrated  from a WAVETEK s i g n a l g e n e r a t o r  i n f i g u r e C.4.  The g a i n o f the t r a n s d u c e r s was e s t i m a t e d  a TEKTRONICS TYPE 581 o s c i l l o s c o p e . to  be the lowest  values obtained  C.2  are only  The c u t o f f frequency  a t which the g a i n was reduced  using  was c o n s i d e r e d by 3 dB.  The  approximate.  System T e s t The  and  frequency  were used i n t h i s t e s t as  transducers'developed  PDP-9 computer i n the h y b r i d  Constant  were connected  t o the h y b r i d i n t e r f a c e  computer l a b o r a t o r y as shown i n f i g u r e C.5.  v o l t a g e s and c u r r e n t s were used as t e s t i n p u t s and were measured  u s i n g the FLUKE d i g i t a l v o l t m e t e r .  The PDP-9 computer was programmed as  40  voltage source  voltage transducer  voltage ) source  current transdi rcer  oscilloscope  FIGURE CA: FREQ. RESPONSE" TEST  voltage source *  precision resistance  •/ voltmeter  voltmeter  voltage source  FIGURE  C.5 : SYSTEM TEST  41  shown i n the f l o w c h a r t In a d d i t i o n , in the  of f i g u r e C.6 and the program l i s t i n g  measurements were made on the h y b r i d  interface i t s e l f  f i g u r e C.8 to determine i t s i n p u t / o u t p u t c h a r a c t e r i s t i c s . g a i n of the i n t e r f a c e was computed assuming l i n e a r i t y  ment e r r o r s were c a l c u l a t e d Test  of f i g u r e  C.7.  as shown  From  this,  and the measure-  using t h i s r a t i o . .  Conditions:  - approx. 66 F. - hybrid  computer l a b o r a t o r y  environment  - g a i n of i n t e r f a c e measured and used to compute measurement - sampling p e r i o d - error  calculated  error  approx. 101 u s e e . / c h a n n e l from worst e r r o r  committed i n 10 s u c c e s s i v e  samples.  Inputs: D.C. V o l t a g e :  H e a t h k i t 0-400 V.D.C. r e g . s u p p l y ; @ 420.4, 350.4, 300.4, 230.5, 160.5, 109.9, 20.18 v o l t s  D.C. C u r r e n t :  Lambda 1-4 V.D.C. r e g . supply; p r e c i s i o n dropping r e s i s t a n c e s : 1(1-.0012), 0.1(1 + .0013), 0.05(1 + .0014)fi. @ 38.19, 33.31, 24.98, 20.02, 15.00, 10.92, 2.50 amperes  C L f A R A / D B l F F E X RBGlSTKK  | S E T Sg^H T o T ^ I C K M Q O £ |  PAUSE  jSer  1  s ^ r J T O r)o<-p MQPe^j  I  |f/JiT7ALfZE  A/O  UJA/T LOOP  j  t  LOAD /AOrti  M O X C(+AAJAJ£L POO. M U X ADDRESS  gee.  START A/D CO«JO£KSIO/J ;O/SABCE  |fAje^emeAJr mo* C ^ A O / O E L . MO.[[  FiOW c/Mr FIGURE  C6  43  F i g u r e C.7:  DATA ACQUISITION PROGRAM LISTING  10  303  100  701104 140200 200200 740001 701607 740000 740000 200200 701607 200201 040300 200200 040301 200301 701407 701306 200202 040302 440302 600122 701117 060010 440301 440300 600115 600100  110  115 120 122  130 131 200 201 202  000000  300 301 302  000000 000000 000000  777760 777746  / CLEAR S I I 11 (A/D BUFFER REG.) / DEPOSIT A ZERO IN 200 / LAC 200 / COMPLEMENT AC / LOAD S & H VIA SOI* 16 to TRACK / NOP / NOP / LAC 200 / LOAD S & H VIA S O I 16 to HOLD / LAC 201 (201) = 777760 / DAC 300 (300) = COUNT / LAC 200 (200) = 000000 /DAC 301 : (301) = MUXADD / LAC 301 #  #  / LOAD MUX ADDRESS DIRECTLY / START A/D CONV.; DISABLE SFC  / LAC 202 : (202) = 777746  / / / / / ./ / / /  DAC 302 : (302) = A/D COUNT ISZ 302 JMP . CLA-E.T.* 1, LOADBUFF, JAM AC CLEAR BUFF /// DAC* 10 ISZ 301 (MUXADD) ISZ 300 (COUNT) JMP 115 JMP 100 _ 1  / -y COUNT / -> A/D COUNT  44  UO.O  7  7  0  voltmeter  No.l  PDP-9  voltAge souice  NO.N  o—  Hybrid Interface  INTERFACE  CHARACTERISTICS FIGURE  C8 :  MEASUREMENTS:  45  REFERENCES  1.  K a b r i e l , B. J . , p r i v a t e communication, Power Group, Dept. of E l e c t . Engrg., U. o f B r i t i s h Columbia, Vancouver.  2.  Bekey, G. A. and K a r p l u s , W. New  3.  York, N. Y.,  H a s l i n , S.,  J . , Hybrid  U.S.A., 1968,  Computation, W i l e y and  125-127.  "An O n - l i n e Computer System f o r P r o c e s s i n g E x p e r i m e n t a l  Waveforms", Summer E s s a y , Dept. of E l e c t . Engrg., U. o f B r i t i s h Vancouver, 4.  D i g i t a l Equipment  Corp., Advanced  Software System M o n i t o r s , D.E.C.,  Chapter 5.  Rothman, James E., " F a s t F o u r i e r T r a n s f o r m S u b r o u t i n e " , Program C a t a l o g , DECUS., Maynard, Mass., 1969, page  6.  Columbia,  1968.  Maynard, Mass., 1968, 5.  Sons,  Library  16-Y.  Birman, P., Kepco Power Supply Handbook, Kepco I n c . , F l u s h i n g , N.  Y.,  1967. 7.  Crawley, B., M.A.Sc. T h e s i s , Dept. of E l e c t . Engrg., U. of B r i t i s h Columbia, Vancouver,  8.  Burr-Brown LI-227,  9.  Research Corp., Handbook and C a t a l o g of O p e r a t i o n a l  Amplifiers:  1969.  Fairchild View,  1969.  Semiconductor I n c . , L i n e a r I n t e g r a t e d C i r c u i t Handbook, M o u n t a i n  Calif.,  1967.  

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