I have a Pinpoint pH monitor and this morning it's reading "-1" on the display. Do the probes need cleaning occasionally or is this some other problem? said:
The probes do need recalibrating and cleaning them prior is a good idea. This doesn't sound like cleaning is the problem, you may be having a noise interference issue, have you moved the cable's around recently. Sometimes a weak battery causes wierd things also even if it's using the power adapter. The pinpoint I had would actually perform better when I just used battery power, it would flake out all the time when I tried using the power adapter.
Cheers,
