5322A
Operators Manual
38
To switch between grounded and ungrounded (floating) output:
1. Push the Setup softkey.
2. Using the cursor keys or rotary knob, highlight High resistance source and
either push the Select softkey or push in the rotary knob.
3. Using the cursor keys or rotary knob, highlight High resistance source GND
and either push the Select softkey or push in the rotary knob.
4. Using the cursor keys or rotary knob, move the cursor to GND On or GND
Off and either push the Select softkey or push in the rotary knob.
5. Push the Exit softkey repeatedly to return to the main display.
The High-Resistance Multiplier may be used to extend the Product range to
10 TΩ. To activate the High-Resistance Multiplier, push the R Mult softkey. Yes
should appear to the right of R multiplier in the PARAMETERS area of the
display. Pushing the R Mult softkey again turns off the resistance multiplier.
The high-resistance multiplier outputs high resistance from 350 MΩ to 10 TΩ with
a maximum applied voltage of 10 kV dc. The multiplier is only used with
insulation resistance testers with a third terminal, commonly called the Guard
terminal. See Calibrate Insulation Resistance Testers with the Resistance
Multiplier. Most testers of this type use a virtual ground-sensing circuit, that
effectively has an input resistance of 0 Ω. The resistance multiplier operation is
based on a passive T-type resistance network, with a nominal multiplication
value of 1000. The exact multiplication value depends on the resistance multiplier
calibration, so refer to the multiplier's calibration data to determine actual output.
The input resistance of the multiplier is approximately 300 MΩ. As mentioned, the
multiplier can be used for checking Device Under Test (DUTs) that use a virtual
ground (current to voltage converter) input as the current sense terminal and an
effective input resistance of 0 Ω.
For DUTs with a finite input resistance and a non-virtual ground on the sense
terminal, the input resistance must be taken into consideration. The Product has
a parameter R multiplier input in the Setup menu for this purpose. The default
value is 0.00 MΩ, with a maximum setting value of 100 MΩ. The input resistance
of the DUT’s sense terminal should be entered into the R multiplier input for the
multiplier to work properly.
Note
The input resistance of the DUT’s sense terminal is different for
various models of megohmmeters. For megohmmeters with a virtual
ground, 0 Ω should be written into the R multiplier input parameter.
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