PH Meter Problem

[balance]

Hi,

I have a PH meter in my tropical tank which controls the flow of CO2 which has been in place for about 3 months. I have it set to PH 7.5 and everything seems happy - however, in the last day the PH is showing as around 3 to 4.

I've tested the water today and the PH is somewhere between 7 and 8 (so pretty much where my water normally would be - definitely not in the 3 to 4 range). I've tried to recalibrate the meter using buffer solutions and for some reason the maximum I can dial into the meter is 7 and with the probe sitting in either solution the reading never settles - varing by around .5 to 1 PH seemingly at random.

To finally get to the point - I'm looking for advice as to where my problem might lie on the meter / probe and any tips for what I might be able to fix my problem.

Many thanks

[fort384]

Did you get the meter used? The pH probe is expendable and has to be replaced every 12-18 months or so to work accurately. While I wouldn't expect an overnight massive shift like you have, before scrapping the meter I would get a new probe. You can usually find them on eBay for pretty cheap.

[balance]

It was purchased new but an ebay cheapie so I'll have a look for a new probe - I didn't realsie they "wear out".

Thanks

[fort384]

Good luck and let us know how it comes out.

Welcome to AA by the way!