Problems with the FE165 pH Amp are very rare.
The problem is most likely caused by inadequate filling of the reference electrode barrel with KCl filling solution, or an issue with the composition of the filling solution (e.g., it has been diluted or has degraded). To correct for both possibilities, it is recommended that any existing fluid in the barrel of the reference electrode is discarded and replaced with fresh KCl filling solution to the correct level.
Other possible explanations of fluctuating pH measurements include:
- The electrode tips are insufficiently or not continuously immersed in the solution. In this case increase the measuring volume.
- The circuit between the pH and reference electrodes is faulty.
- Ground loops are present. Ensure no other probes/electrodes are placed in the solution unless they are isolated from the same ground (mains).
- The glass pH electrode was stored incorrectly and is not functioning correctly.