Operation And Function; A) General - Voltcraft Rim 1000 Bedienungsanleitung

7. Operation and function

a) General

The accumulator internal resistance measuring device "RIM
1000" has a special, manual measuring device housing. An LC
display is integrated; the measuring cables are firmly connected
to the device to avoid contact resistances.
The measuring device can determine the internal resistance in
just a few seconds.
In principle, measurement of the internal resistance is
quite simple. The accumulator or accumulator pack is
discharged at a high, defined current and the drop in
voltage compared with the uncharged status is
determined. The difference in voltage divided by the
load current then gives you the internal resistance.
In practice, however, this measurement is not so simple. On the
one hand, it concerns very low differences in voltage in the 'milli'-
volt range (mV) and, on the other, the measuring device has to
cope with at least briefly high discharge currents and the asso-
ciated loss in power.
In addition, exponential results can only be attained when the
detection of voltage takes place directly on the accumulator.
Otherwise, the drops in voltage on the measuring cables would
falsify the result markedly.
To fulfil these requirements, quite special measurement
cables are used fort he measuring device "RIM 1000"
(4-cable measuring technology).
The measuring cables are firmly connected to the measuring
device. This prevents the contact resistances of conventional
measuring device jacks as described at the beginning.
Two cables per measuring cable are conducted to the probe tips
One conducts the discharge current, the other is responsible for
the measurement.
The probe tips are sprung which should lead a relatively even
pressure on the measuring point (e.g. pole caps of the accumu-
lator).
The high discharge current flows over the big round contact. The
small pointed contact is used for recording the measured values
directly on the measuring point (e.g. pole caps of the accumula-
tor).
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