SECTION 
1 
GENERAL INFORMATION 
1.1 
INTRODUCTION 
The  Model  197  is  a  six  function, 
5?h 
digit  resolution 
autoranging digital multimeter  with a 
+-220,000 
count LCD 
(Liquid Crystal Display). This 
A/D 
range is greater than the 
normal  +-199,999 count 
A/D 
used in many 
5?h 
digit DMMs. 
The 
5% 
digit resolution allows the Model 197 to measure 
DC 
voltage from 1pV/count to 
1OOOV. 
AC 
voltage  and current 
measurements  are standard in the Model  197. TRMS ACV 
capability  ranges from IpVlcount to 
750V. 
The Model  197 
measures resistance from 1mQ to 220MQ on seven resistance 
ranges. The Model 197 has six current  ranges  that  measure 
current from 1nA (lO-9A)  to 10A. 
The dB function  makes 
it 
possible to compress a large range 
of  readings into a much smaller scope. The Model 197 dBm 
measurements are referenced to the standard 
600Q 
impedance 
but can be modified  with  the use of  relative 
(REL) 
feature. 
The  Model  197 has  two  IEEE-488  interface  options:  The 
Model  1972 and the Model  1973. These optional  interfaces 
enhance  the  capabilties  of  the  Model  197 by  allowing  pro- 
grammed control over the IEEE-488 bus. The Model 1972 also 
includes an analog output. The bus commands are the same 
for each interface and respond  to IEEE-488 protocol. 
6. 
5% 
Digit  Resolution-The  Model  197 has  a  +220,000 
count  A/D that  surpasses  the  more  common  k199,999 
count A/D. 
7. 
Four 
Terminal  Ohms-These  terminals  are  used  to 
eliminate  the  voltage  drop  across  the  current  carrying 
leads. 
8. 
Sensitivity-The  Model 197 has 1pV, ImQ and 1nA sen- 
sitivity. The IpV of  sensitivity allows minute levels of off- 
set, temperature etc. A 1nA sensitivity allows low current 
measurements  without  special  equipment.  Measure 
leakage, bias and offset current. A ImQ sensitivity allows 
easy low resistance measurements. 
1.3 
WARRANTY  INFORMATION 
Warranty information may be found on the inside front cover 
of  this  manual. Should 
it 
become  necesary  to  exercise  the 
warranty, contact your Keithley representative 
or 
the factory 
to  determine  the  proper  course  of  action.  Keithley  In- 
struments  maintains  service  facilities  in  the  United  States, 
United  Kingdom  and throughout  Europe.  Information  con- 
cerning the application, operation 
or 
service of  your instru- 
ment may be directed  to the applications engineer at any of 
these locations.  Check the inside front cover for addresses. 
1.4 
MANUAL ADDENDA 
1.2 
FEATURES 
The Model 197 includes the following features: 
1. 
2. 
3. 
4. 
5. 
Six Measurement  Functions-DCV,  ACV,  DCA,  ACA, 
OHMS 
and dB all built in. 
(REL) Relative Mode-The  relative mode allows offsets to 
be  nulled  out (e.g. test  lead resistance  for low resistance 
measurements)  and  selects  a  variety  of  reference  im- 
pedances for dB measurements. 
Digital Calibration-A  non-volatile 
RAM 
stores calibra- 
tion constants and can be performed from the front panel 
or 
over the IEEE-488 bus. 
Data Logger-A  data storage buffer  is included to allow 
up to 
100 
readings and minimum/maximum readings be 
internally stored at a user selectable rate. The buffer may 
be read  and controlled  from  the front panel 
or 
over the 
IEEE-488 bus. In the talk-only mode, the output rate can 
also be programmed. 
Autoranging-The  Model 197 includes a fast autoranging 
feature for easier measurements. 
Information concerning improvements or changes to this in- 
strument which occur after the printing 
of 
this manual will be 
found on an addendum  sheet included  with  this manual. Be 
sure to review these changes before  attempting to operate 
or 
service the instrument. 
1.5 
SAFETY SYMBOLS AND TERMS 
The  following  safety  symbols  and  terms  are  used  in  this 
manual or found on the Model  197. 
The symbol 
A 
on the instrument denotes the user should 
refer to the operating instructions  in this manual. 
The symbol  &n  the instrument  denotes that a potential 
of 
1OOOV 
or 
more may be present on the terminal(s). Stand- 
ard safety practices should be observed when such dangerous 
levels are encountered. 
1-1 
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