The Model 197A is a six function, 5-1/2 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 5-1 /2 digit DMMs.
The 5-1 /2 digit resolution allows the Model 197A to measure
DC voltage for 1µV/count to 1000V. AC voltage and current
measurements are standard in the Model 197A. TRMS ACV
capability ranges from 1µV/ count to 750V. The Model 197A
measures resistance from 1mΩ. to 220MΩ on seven resistance
ranges. The Model 197A has six current ranges that measure
current from 1nA (10⁻⁹A) to 10A.
The dB function makes it possible to compress a large range
of readings into a much smaller scope. Model 197A dBm
measurements can be referenced to 50, 75,93,135, 300 or 600Ω
(default), but can be modified with the use of the relative
The Model 197A has two IEEE-488 interface options: The Model
1972A and the Model 1973A. These optional interfaces enhance
the capabilities of the Model 197A by allowing programmed
control over the IEEE-488 bus. The Model 1972A also includes
an analog output. The bus commands are the same for each
interface and respond to IEEE-488 protocol.
The Model 197A includes the following features:
1. Six Measurement Functions — DCV, ACV, DC A, ACA, OHMS and
dB all built in.
2. (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 impedances
for dB measurements.
3. Digital Calibration — A non-volatile RAM stores
calibration constants and can be performed from the front
panel or over the IEEE-488 bus.
4. 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.
5. Autoranging — The Model 197A includes a fast autoranging
feature for easier measurements.
6. 5-1/2 Digit Resolution — The Model 197A has a ±220,000
count A/D that surpasses the more common ±199,999 count A/D.
7. Four Terminal Ohms — These terminals are used to
eliminate the voltage from across the current carrying leads.
8. Sensitivity — The Model 197A has 1µV, lmΩ and 1nA
sensitivity. The 1µV of sensitivity allows minute levels of
offset, temperature etc. A 1nA sensitivity allows low
current measurements without special equipment. Measure
leakage, bias and offset current. A 1mΩ sensitivity allows
easy low resistance measurements.
9. Electroluminescent Display Backlight — A switch
selectable electroluminescent display backlight used to
enhance the liquid crystal display under low light or dark
10. dB Reference Impedances — Selectable dB reference
impedances of 50Ω, 75Ω, 93Ω,135Ω, 300Ω and 600Ω (default).