ground reference problem?

[laurentm]

I think I lost the ground reference for the pH and ORP probes (I have an ACIII pro). The only way I can get a correct reading right now is if I place the conductivity probe next to the other probes in the sump.

The temperature reading seems ok, but the titanium tip is not connected to anything at the jack side. I tested it with an ohm meter. Is there any way I can repair the temperature probe or do I need a new one? Can I force the ground reference with another titanium probe?

 

[clp]

The titanuium tip should be connected to the middle terminal on the temperature probe connector. If not the internal wire is broken somewhere. If it is broken at the probe end, it will be impossible to fix. If broken at the connector end, a new connector could be installed. If the AquaController's ground was connected to the titanium probe, it would work as a ground reference.

Curt

 

[laurentm]

I ended up connecting an external titanium probe to the middle terminal on the temperature probe and placing it right next the pH and ORP probes.

The pH and ORP look ok now except that I can see immediate changes in temp and pH reading if the Conductivity probe is connected but outside the water (it usually sits in its own drip cup). The readings are higher (by .5 for the temp and .03 for the pH) when the conductivity is dry. If I put the Conductivity probe back in the water (isolated from the tank water), the readings go down!

Any idea what could cause this?