PH now read 7.0

[sherman]

Last week I reload a new sketch after adding ATO with one float switch using relay 6.
After that PH drop to 7.0.
I try recalibrate with PH 7 and PH 10 fluid a few time.
PH still reading 7.0
My PH pen read 8.0 .
I remove the probe from the tank and fill a cup with tank water .
Put the probe into the cup of tank water this time it read 8.0.
I remove the float switch connector from the head.
Reset the head by power off then on again.
Still the PH read 7.0.
Is it the probe problem?
Please help

[lnevo]

Sounds like either the switch still is an issue or somewhere else your getting stray voltage. If it reads correctly in an isolated cup of water than ra is good and probe is good.

[sherman]

Thank You for the info.
I will check for stray voltages.

[ReEfnWrX]

Just curious as I will be receiving my RA+ soon. Would grounding his sump/DT prevent the affects of stray voltage on his probes? Or is the only options replacing/fixing whatever is putting the current in the tank and/or buying the expansion modules with galvanic isolation?