strange behaviour during pH calibration

[redlion]

i have just upgraded to P3 and have been calibrating the probes, as i only have pH fluids of 4 and 7 i have used these until i get hold of a 7 & 9/10,
this is what happened -

firstly i calibrated using 4 & 7, i put probe into tank and get a reading of 3.00??

then i calibrated again using 4 & 7 and put probe into tank and it was 3.00 again, i put the probe back into 7 and it reads 7, i put probe into tank, it was 3, puting probe into 4 moves reading back to 4... and then climbs to 4.75??

then trying to identify a pattern i put it back into 7 and it rises to 7.5 before dropping and stabalising at 6.5-6.6, finally i placed probe in a high flow area of my tank and its a stable 3.00

before doing this i cleaned the probe in a cleaning solution i had from my aquatronica days, i cant see how this would have made it behave like this but im baffled why its reading like it is, all indications during the calibration process seem to be positive.

any thoughts appreciatted

[GHL Support]

Hello,

what happens if you measure the pH-value in a glass with aquarium water, which value is then displayed?

There could be some electromagnetic fields in/at the aquarium which disturb the measurement.

[UK-GHL]

I spoke to Ian this morning, the probe tip had been damaged and the glass junction was missing. New probe time, unfortunately.

Steve