The electrodes are manufactured to a very high specification and checked before dispatch. However they are installed and exist in some aggressive environments so problems can occur with the units during and after installation. To help our clients to avoid and identify these problems we have listed some of the common problems.
After installation the potential drifts to zero on the low impedance setting.
- This may indicate that there is poor contact between the electrode and the concrete or soil. In very dry conditions the contact may be restored once the moisture returns. Alternatively the electrode will need to be replaced or reinstalled.
After installation the potential drifts to zero on the high impedance setting.
- This may indicate a break in the cable insulation.
Electrodes exhibit open circuit below -10°C
- At very low temperatures the pore water in the concrete freezes and the electrode loses contact with the electrolyte. The electrode will recover once the temperature rises.
Prior to installation the electrodes are “calibrated” on site and checked against the laboratory calibrations. The results do not correspond.
- The electrodes are very sensitive units and it is not possible to repeat the calibration test under site conditions and obtain identical readings. The electrodes should undergo functional checks on site to ensure the readings are stable prior to installation.
The electrodes are pre potted in a mortar cylinder and checked again to see if the readings correspond to the pre encapsulation test within +/- 3mv. The results are outside this range.
- The readings will not necessarily be within this range due to a position dependence variation in the potential. This check should be used to confirm that the potentials are steady and thus indicate that there is good contact between the mortar and the electrode end sensor.
High positive readings are recorded after installation
- Check the readings again at high and low impedance.
- Disconnect the electrodes for one month to see if they recover.
- Check that the CP system wiring is correct.
- Are the electrodes being polarized by the measuring system?