pH probe placement?

[shullat]

sorry roger but i have another question. I placed the calcium reactor in my sump in the return section, the probe is in the skimmer section just before the baffles. The wird thing is the Ph is jumping around like crazy ...it was 8.32 for most of yesterday, and today it went up to 9.3 then back down to 7.2 at night. Could the vibrations from the skimmer, or the current be causing this. I can assure you that no additions were made that could alter the pH in such a drastic manner. Where is the best place to place the probe?

 

[rvitko]

It is best to place the probe in a quieter area of the tank preferrably farthest from the reactor. It sounds like a possible stray voltage issue. Imagine an electrode as a 100mV battery, essentially that is what it is. Instead of lead and lead oxide and sulphuric acid it has platinum, platinum oxide and KCL. The pH induces a change in current in millivolts from say 120mV-80mV and if any stray volatge is present it can cause erratic readings. The other thing that can cause this is using a battery and the power supply on the controller, if you have the solenoid and power supply, no battery should be used. You may need a ground probe for the tank.