Fluke 8842A User Manual

8842A
Instruction Manual
5-12
Resistor R701, precision resistor network Z701, and transistor/zener diode combination
U701 are produced as a matched set so that the output of U702A is precisely -7.00000V.
This output is remotely sensed at the pins of the custom A/D IC (U101). Diode CR701
prevents the output from going positive at power-up.
U702B functions as an inverter to provide the +7.00000V output and to supply the
reference amplifier. The gain of U702B is set by the two 20 kΩ resistors in the resistor
network Z702.
5-15. OHMS CURRENT SOURCE
The Ohms Current Source (Figure 5-7) provides a precise test current for the ohms
functions. The first stage (U401, R401, and Q401) produces a precise reference current,
using precision resistor R401 and a -7.0000V reference voltage from the Precision
Voltage Reference.
f5-07.wmf
Figure 5-7. Ohms Current Source

Fluke 8842A Specifications

General

Maximum Voltage	1000 V
Maximum Current	2 A
Operating Temperature	0°C to 50°C
Weight	2.5 kg
DC Voltage Range	100mV to 1000V
DC Current Range	0 to 2 A
AC Current Range	0 to 2 A
Frequency Range	20 Hz to 20kHz
Basic Resistance Accuracy	0.01%
Dimensions	216mm x 88mm x 280mm
Resistance Range	200 Ω to 20 MΩ