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TABLE OF CONTENTS

SECTION I .UNPACKING A N D INSTALLATION

Unpacking and I n s p e c t i o n ....................... 1-1
I n i t i a l Adjustments ............................
.....................
I n s t r u c t i o n s f o r Bench Use
1-1
1-1
.................
I n s t r u c t i o n s f o r Rack Mounting
Safety Precautlons ............................. 1-1
1-2

SECTION I1 .SPECIFICATIONS ...... ................... 2-1

SECTION I11 .M N A OPERATION
AUL

General ........................................ 3-1
Connections ....................................
..........................
Four-Wire C o n n e c t i o n s
3-1
3-1
...........................
Two-Wire C o n n e c t i o n s
............................
Numeric V a l u e E n t r y
3-4
3-4
Step Control
Memories
...................................
....................................... 3-5
3-5
...................
Two-Wire/Four-Wire S e l e c t i o n
2724A W i t h o u t CPR.............................. 3-6
3-6
2724A With CPR .................................
Slow-Mode and Fast-Mode (2724A W i t h o u t CPR)....
3-6
3-7
Two-Wire Key (2724A With CPR)
Fast-Mode Key (2724A With CPR)
..................
................. 3-7
3-8
Card PNT Key
PPM DEV Key
...................................
.................................... 3-8
3-9

SECTION I V .IEEE-488 INTERFACE OPERATION
IEEE.488.
Definitions
;...... .....
An E x p l a n a t i o n O f The Bus
.................................... 4-1
4-1
General ........................................ 4-3
Simple Commands and Examples ................... 4-5
Advanced Commands and Examples .................
.............
SRQ. S e r i a l P o l l and P a r a l l e l P o l l
4-7
4-8

SECTION V .THEORY OF OPERATION
General ........................................ 5-1
Functional Description ......................... 5-1
Detailed Circuit Descrlptions ..................
............................
Reference R e s i s t o r s
5-1
5-1
REF B u f f e r..................................... 5-2
...............................
U n i t Gain B u f f e r
................................
Ohms M u l t i p l i e r
5-2
5-3
........................
V a r i a b l e Gain A m p l i f i e r 5-3
TABLE OF CONTENTS (Cont.) T

MDACfs ......................................... 5-3
Output B u f f e r .................................. 5-4
...................................
A/D C o n v e r t o r 5-4
.............
P r e - S c a l i n g and I n p u t M u l t i p l e x i n g 5-4
Reference Voltage Generator ....................
..............................
FET S w i t c h D r i v e s
5-5
5-5
Current Balance ................................ 5-5
Floating Section Isolation
Microprocessor
.....................
................................. 5-5
5-6
A/D Convertor Logic ............................
Opto-Isolator Latches/Drivers .................. 5-6
5-6
Microprocessor (MPU)
Address Decode
...........................
................................. 5-6
5-8
Memory .........................................
Clock. D i s p l a y and Keyboard .................... 5-8
5-8
.............................
IEEE-488 I n t e r f a c e
Power S u p p l i e s................................. 5-9
5-9

SECTION VI .CALIBRATION AND MAINTENANCE
6.1 A Brief Description of the Calibration Procedure .....6-1
...............................................6-2
6.2 General
...........................................
1

6.3 Calibration 6-3
6.3.1 Step 1 (Non CPR units) ................................
................................6-2
6.3.2 Step 2 (Non CPR units) 6-,2
6.3.3 2724 CPR Adjustment Procedure .........................6-3
6.3.4 Front Panel Calibration ...............................6-5
............6-6
6.3.5 Step 3 Active Mode Calibration (all units)
6.3.6 Step 4 CPR Calibration (option CPR only) ..............
....................6-9
6.4 Step 5 -
Completion of Calibration
6.5 Automatic Calibration ................................ 6-9
6-10
6.6 Troubleshooting ......................................
6-10
SECTION V I I .AVAILABLE OPTIONS

General ........................................
.................................... 7-1
O p t i o n TL-1 7-1
....................................
O p t i o n RX-3
.....................................
O p t i o n BBL
7-1
7-1
...............................
O p t i o n s GP1. GP2
............................
C a l i b r a t i o n K i t M24
7-1
7-1
.....................................
O p t i o n CPR
SP-2 ........................................... 7-1
7-1

SECTION V I I I .USEFUL HINTS
General ........................................ 8 - 1 -
Unstable Test Currents ......................... 8-1
P
TABLE OF CONTENTS (Cont.)

Wheats t o n e B r i d g e Comparison t o S t a n d a r d
Resistors ..................................... 8-2
................ 8-1
Use With High R e s i s t a n c e M e t e r s

Use With A c t i v e Feedback C u r r e n t S o u r c e s
.............................. 5-2
.......
~ i n e nterference
~
........................ 8-2
Additional H e l p f u l H i n t s 8- 3
SECTION I X - DIAGRAMS

9.1 General ........................................ 9-1

SECTION X - PARTS LISTS
10.1 General........ .......................................... 10-1
LIST OF TABLES

1.
1 . V o l t a g e S k l t c h S e t t i n g s and F u s e R a t i n g s......... 1-1
2.1 . General S p e c i f i c a t i o n s ...................... 2-1
2-2 . O p e r a t i n g S p e c i f i c a t i o n - ......................... 2-2

3.l.(a) F r o n t P a n e l C o n t r o l s (2724A and 2724CPR) ......... 3-2
3-l.(b) F r o n t P a n e l C o n t r o l s (2724A W i t h o u t O p t i o n CPR) .. 3-3
3.1.(~) F r o n t P a n e l C o n t r o l s (2724A With O p t i o n CPR) ..... 3-3
E r r o r Message D i s p l a y s ........................... 3-4
.
3.2 .
4.1
42
.
.
.
ASCII C h a r a c t e r and Bus Messages ................. 4-4
SRQ B i t P a t t e r n s ................................. '4-9

6.1 . T r o u b l e s h o o t i n g Guide ............................ 6-8

LIST OF ILLUSTRATIONS

F i g u r e 3-1 Slow Mode E q u i v a l e n t C i r c u i t ................... 3-6
................... 3-8
F i g u r e 3-2 F a s t Mode E q u i v a l e n t C i r c u i t
F i g u r e 3-3 CPR Mode E q u i v a l e n t C i r c u i t .................... 3-7
F i g u r e 6-1 C a l i b r a t i o n C o n n e c t i o n s ........................ 6-4
SECTION I - UNPACKING AND INSTALLATION

1.1 UNPACKING AND I N S P E C T I O N

I f t h e s h i p p i n g c a r t o n i s damaged, r e q u e s t t h a t t h e c a r r i e r ' s
a g e n t b e p r e s e n t when t h e u n i t i s u n p a c k e d . I f , when u n p a c k e d ,
t h e u n i t shows e x t e r n a l damage, t h e c a r r i e r ' s a g e n t s h o u l d
a u t h o r i z e repairs before the unit is returned t o the factory.
I f t h e s h i p p i n g c a r t o n i s damaged, t h e u n i t may h a v e s u f f e r e d
i n t e r n a l damage i n t r a n s i t t h a t may n o t b e e v i d e n t u n t i l t h e
u n i t i s operated o r t e s t e d t o v e r i f y conformance with i t s
specifications. I f t h e u n i t f a i l s t o p e r f o r m o r f a i l s t o meet
t h e p e r f o r m a n c e s p e c i f i c a t i o n s o f S e c t i o n 11, n o t i f y t h e
c a r r i e r ' s a g e n t and t h e n e a r e s t V a l h a l l a S a l e s O f f i c e . Retain
the shipping carton for the carrier's inspection. DO NOT
r e t u r n equipment t o V a l h a l l a S c i e n t i f i c o r a n y o f i t s s a l e s
o f f i c e s p r i o r t o o b t a i n i n g a u t h o r i z a t i o n t o do s o .
1.2 I N I T I A L ADJUSlMENTS

The o n l y adjustments r e q u i r e d b e f o r e p l a c i n g t h e u n i t I n
o p e r a t i o n are t o s e t t h e r e a r p a n e l s w i t c h t o t h e l o c a l power
v o l t a g e a n d v e r i f y t h a t t h e p r o p e r f u s e i s i n s t a l l e d as l i s t e d
i n T a b l e 1-1.
m
T a b l e 1-1. Voltage Switch S e t t i n g s and
Fuse R a t i n g s .

SUPPLY SWITCH FUSE
VOLTAGE SETTING RATING

115 0.5 Amp S l o B l o
230 0 . 2 Amp S l o B l o

1.3 INSTRUCTIONS FOR BENCH U S E

The u n i t i s d e l i v e r e d w i t h a l l r e q u i r e d h a r d w a r e f o r b e n c h u s e
i n s t a l l e d and s p e c i a l i n s t r u c t i o n s f o r u s e i n t h a t manner are
n o t necessary. However, b e f o r e c o n n e c t i n g t h e u n i t t o t h e
l o c a l power s o u r c e , v e r i f y t h a t t h e power c o r d i s e q u i p p e d w i t h
a three-terminal connector (see the Safety Instructions o f
paragraph 1.5).
1.4 INSTRUCTIONS FOR RACK MOUNTING

O p t i o n a l b r a c k e t s are a v a i l a b l e f o r m o u n t i n g t h e Model 2 7 2 4 A i n
an equipment r a c k . These a r e l i s t e d i n S e c t i o n V I I . The s i z e
F o f t h e u n i t and t h e l o c a t i o n o f i t s c e n t e r o f g r a v i t y d i c t a t e
t h a t i t s h o u l d b e s u p p o r t e d on b o t h s i d e s a l o n g i t s e n t i r e
l e n g t h through the u s e o f " t r a y s " o r s l i d e s . If i t i s t o b e
t r a n s p o r t e d w h i l e mounted i n a r a c k , i t s h o u l d b e s u p p o r t e d
s u c h t h a t movement i n a n y a x i s I s n o t p o s s i b l e .
Note t h a t t h e s p e c i f i c a t i o n s l i s t e d i n S e c t i o n I1 i n d i c a t e t h a t
accuracy o f .the u n i t Is degraded at abnormally h i g h
temperatures. T h e r e f o r e , i t i s recommended t h a t l l s p a c e r l l
p a n e l s a t l e a s t 1.75 i n c h e s h i g h be . i n s t a l l e d b e t w e e n t h i s a n d
a n y o t h e r u n i t s i n t h e rack t o i n s u r e freedom o f a i r flow.
Under no c i r c u m s t a n c e s s h o u l d t h e a m b i e n t a i r t e m p e r a t u r e
a r o u n d t h e u n i t e x c e e d 50