Resistance Measurements - TECPEL DMM-129A Operating Instructions Manual

4. Switch OFF or disconnect the circuit to be measured from all power
sources, connect the multimeter in series with the conductor in which
the current to be measured flows.
5. Switch ON the circuit. Note the reading.
6. Switch OFF or disconnect the circuit and remove the test leads from
multimeter.
A common abuse of multimeters in to attempt to measure a voltage
while the test leads are still plugged into the current input terminals.
This basically puts a short circuit across the voltage source since
current ranges have a low impedance. If the voltage source is typi-
cally 240VAC or a 3-phase industrial voltage (415V), very high
fault currents can result. This is why all current input terminal are
fused. If the fuses blow they must only be replaced by the equiva-
lent ones otherwise the safety of the instrument may be impaired.
7. Never apply a voltage between the COM terminal and current
terminals.
8. When switching between current ranges to obtain greater accuracy
and better resolution, completely de-energize the circuit to be mea-
sured before changing the range.

RESISTANCE MEASUREMENTS

Turn off power on the test circuit and discharge all capacitors before
attempting in-circuit resistance measurements. If an external volt-
age is present across a component, it will be impossible to take an
accurate measurement of the resistance of that component.
CAUTION
CAUTION
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