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During the measuring process, wait until the contact resistance becomes stable before
taking a reading. This may take a few minutes.
Select the most appropriate settings.
Select the most appropriate stack in order to stop the reading when the chargeability
and the resistivity responses are stable. Depending on your sample and contact
resistance, the number of stacks needed to obtain stable values will vary.
We suggest using the same timing and windows than your field IP survey. Otherwise, a
timing of two (2) seconds and arithmetic windows give good results.
Use the appropriate mode (constant current or constant voltage).
There are two modes of measurement, voltage and current. In order to determine
which one to use, the contact resistance value (Rs) can be a good indication. For a Rs
between 1 kOhm and 24 kOhms both modes are possible. However, we suggest
selecting a constant current for an Rs lower than 1 kOhm and a constant voltage when
Rs is greater than 1 kOhm. In voltage mode make sure that the Vp (mV) is greater than
half of the selected voltage and in current mode make sure that the I (uA) is almost the
same value of the selected current. If there is saturation, the reading may not be
reliable. In that case, try a lower current or a lower voltage.
For better results, take the average of several readings on each core sample.
Instrumentation GDD Inc.
Constant current
Rs = 1 kOhm
Constant current
Rs = 1 kOhm
Rs = 24 kOhms
Constant voltage
Constant voltage
2018-09-18
Page 8
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