G) Measuring Resistance "Ω - VOLTCRAFT R-200 Bedienungsanleitung

g) Resistance measurement "Ω"
Make sure that all the circuit parts, switches and components and other objects of
measurement are disconnected from the voltage and discharged.
The Milliohm meter allows you to measure resistances in normal measurement ranges from 0.1 Ω to 40
MΩ using the 2-lead measurement procedure and also allows the precise measurement of low Ohm
resistances from 0.1 mΩ to 40 Ω using the 4-lead measurement procedure.
The 2-lead measurement includes the resistance of the measuring leads in the total
measurement. The measurement lead resistance is approx. 0.5 Ω. This low value can
be disregarded in a measurement range up to 40 MΩ. The switching diagram is illus-
trated on the right:
Both resistances "R E1" and "R E2" indicate the measurement leads. "R" indicates the
measured object. All three resistances contribute to the measured value.
The 4-lead measurement connects a current and voltage measurement circuit.
According to Ohm's law, all currents in a series circuit are equal. The current mea-
surement in the measurement circuit is independent of the measurement location.
The voltage measurement is carried out at high Ohms so that the measurement circuit
is not loaded and the measured values are not falsified. The additional voltage mea-
surement then allows the resistance to be measured without loss through cables (for-
mula: R = U/I). The switching diagram is illustrated on the right:
The two measurement methods are explained in the following.
Proceed as follows to measure the resistance using the 2-lead procedure:
- Turn the DMM on and select measuring range "Ω".
- Plug the red single measuring lead into the Ω -measuring socket "E2"
(10) and the black measuring lead into the COM measuring socket "E1"
(13).
- Check the measuring leads for continuity by connecting both measuring
probes with one another. The resistance value must be approximately 0 -
0.5 Ohm (inherent resistance of the measuring leads).
- Connect the measuring probes to the object to be measured. As long as
the object to be measured is not high-Ohm or interrupted, the measured
value will be indicated on the display. Wait until the displayed value has
stabilised. With resistances >1 MΩ this may take a few seconds.
- If "OL" (overload) appears on the display, you have exceeded the mea-
suring range or the measuring circuit has been broken.
- After measuring, remove the measuring leads from the measured object and turn the DMM off.
If you carry out a resistance measurement, make sure that the measuring points which you con-
tact with the measuring probes are free from dirt, oil, soldering paint or similar. An incorrect
measurement may result under such circumstances.
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