Guildline 6530 Series, Руководство оператора

Страница: 151 / 158

Section 8
OM6530-C1-00
19 November, 2019
8-10
8.7. MEASUREMENT TECHNIQUE
8.7.1. LARGE VALUE RESISTOR MEASUREMENT TECHNIQUE
The measurement of very large value resistors presents special challenges for the
operator. The measurement is often rendered meaningless unless certain precautions are
taken.
8.7.2. ENVIRONMENT
The test equipment and the test sample should be located in a clean dry area where the
temperature is relatively constant near 23

C. The air humidity should be between 20 %rH
and 40 % rH. Ionized air and ionizing radiation should not be present in the test area.
8.7.3. SAMPLE PREPARATION
It is very important to prepare the test sample properly so that unwanted parallel leakage
paths are reduced as much as possible. The condition of the insulation surface between
the sample terminals is very critical since this usually forms a significant source of
electrical leakage. The surface must be dry and free of conductive salts or other deposits.
8.7.4. TEST LEAD ROUTING
Although it is good general practice to use shielded test leads (shielded wires with the
shields connected to ground) it is especially important with higher value test resistors.
Shielded test leads shunt unwanted leakage current away from the electrometer circuit.
8.7.5. CAPACITIVE TEST SAMPLES
Test samples that store electrical charges and have long time constants can be difficult to
measure using the autoreverse feature of the TeraOhm Bridge-Meter. You can adjust the
autoreverse parameters or, deactivate autoreverse until a stable resistance reading is
displayed with one test voltage polarity and then manually reverse the polarity. The
reading from both polarities should be recorded and an average computed.
The true resistance of the sample is the numerical average calculated from the two
readings taken. This technique allows the sample sufficient time to be measured properly.