Types Of Megohmmeters And Use Of The Resistance Multiplier - Fluke Calibration 5322A Operator's Manual

Types of Megohmmeters and Use of the Resistance Multiplier

From a functional point of view, megohmmeters have these designs:
a. Two terminal meters. Terminal meters are equipped with two single sense
terminals usually measuring a resistance ratio against an internal range
resistor. The meters require two pole resistance standards for calibration. The
meters can be calibrated with the Product up to 100 GΩ but not in the
extended range with the resistance multiplier adapter. Typical examples are
models Fluke 165x and other hand-held ohmmeters and multimeters.
b. Two terminal meters with a third Guard terminal. The guard terminal is used
the most for electrostatic shielding to avoid spurious leakage currents flowing
along the surface of objects in the measurement area. The meters can be
calibrated with the Product up to 100 GΩ but not in the extended range with
the resistance multiplier adapter.
c. Three terminal meters with a proper third terminal (COM or GUARD or
GROUND) and with a virtual μA-meter low sense terminal. The COM
terminal is used as a common terminal of the source of test voltage and the
sense μA-meter. The meters can be calibrated both directly by the Product
and the resistance multiplier adapter.
d. Three terminal meters with a third terminal (COM or GUARD or GROUND)
and with a μA-meter that has a fixed input resistance in the low sense
terminal. The COM terminal is again used as a common terminal of the
source of test voltage and sense μA-meter. The meters can be calibrated
directly with the Product and with the resistance multiplier adapter. The input
resistance in the low meter terminal must be known and entered as a
correction in the Product (Setup>High resistance source>R multiplier
input). The meter input resistance is usually specified in its operation
manual.
Multifunction Electrical Tester Calibrator
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