INSTRUMENTATION. AND EQUIPMENT
High resistance voltmeter.
Two lengths of flexible cable, each fitted with a voltmeter connector and a crocodile clip.
1.1 Place the electrode in the ground.
1.2 Connect the electrode to the positive pole of the voltmeter.
1.3. Connect the negative pole of the voltmeter to the pipeline test point connection.
1 4. Move the electrode in 1/2 m steps at a 1m radius around the test post.
1.5. Record the lowest and highest voltage readings on the meter.
1.6 Place the electrode at the point which showed the lowest voltage and record the voltages at 1 minute intervals over a period of 10 minutes.
This will show if there is a fluctuating in the voltage at this location. This could be due to the ground potential fluctuating or the metal potential fluctuating.
If there is any fluctuation then further tests are necessary in accordance with other procedures, described later.
These measurements will show the degree of error inherent at this location, due to variations in the ground potential, at the exact point of contact.
These variations will be due to each contact point having a different potential and could be due to currents flowing through the ground resistance or could be due to 'teluric effects' which are static and constant.
Such records can be used to correct readings previously recorded.