Section 3
3-56
3.8.3. Resistance Measurement - High Ohms - 100 k Rs
100 M; Rx 1 G
Refer to Figure 3-6 for External High Voltage (HV) power supply connections and to Figure
3-7 for Internal HV power supply connections. Figure 3-8 details a suggested guarding
interconnection for the high resistance measurement mode.
The Model 6675A bridge in its High Ohms mode enables measurement of resistance values
up to 1 G:100 M (Rx:Rs). This is a 2-terminal measurement. In this measurement mode
there is a ±90 mA current source with a 30 volt compliance available on the Program Out
terminals in order to drive a Model 9607 High Voltage Reversing Switch directly. Also in
this measurement mode the test voltage set in the measurement setup is available at the High
Voltage and terminal (referenced to ground Rx) once the measurement has been started.
3.8.3.1. High Ohms Measurements - General Procedures
Step 1) Connect one end of the resistor to be measured to the Rx-C
2
, P
2
terminals (use one of the shorting bars provided to short the Rx-P
2
to
Rx-C
2
terminals)
Step 2) Connect one end of the reference resistor to the Rs-C
2
, P
2
terminals
(use one of the shorting bars provided to short the Rs-P
2
to Rs-C
2
terminals).
Step 3) Connect the free end of the Rs and Rx resistor to the internal or
external HV supply (make sure the external HV supply is disabled
first!).
NOTE:
To minimize errors in this 2-terminal measurement introduced by the wire
interconnects, the wiring from the HV supply to the Rs and Rx resistors and the
wiring from the Rs and Rx resistors to the front panel should be as short as
possible.
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