What is an electrode test?
An electrode test, or electrode contact test, is a feature on the ABEM Terrameter LS2 which checks the quality of the electrical connection between each electrode in your resistivity array and the ground.
The electrode test is the first step of data acquisition and should always be carried out to avoid acquisition of poor quality data from inadequate ground contact.
The test is made using the “focus one” method, in which the resistance of each electrode is measured against all the other electrodes. If the electrodes are all properly connected and well grounded, and the measured ground resistance falls beneath the designated threshold, the full measurement sequence will commence immediately after the electrode contact test has finished.
If any electrode registers a high contact resistance, the test fails and the instrument progress log will register how many electrodes have not passed the test. The measurement process will be stopped to wait for instruction from the operator. A separate list of all electrodes gives the detailed test results, including electrode positions, contact resistance and number of times each electrode will be used in the coming measurement. The electrodes which have not passed can then be checked and remedied, before the electrode test is re-made.
There are two threshold levels that can be defined in an electrode test, namely “bad” and “fail”. Typically, “bad” is set to an ‘ideal’ level that you hope all contact resistances fall below (1000 or 5000 Ohms) whilst the “fail” threshold is set to identify those electrodes with no contact at all (e.g. 300 kOhm); potentially indicating a missed connection or cabling problem.
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