Calibrate PH Meter questions

[byronyasgur]

I just bought a cheap PH meter - looks like this one

Some solution came with it and the instructions for making that up said it was OK to use tap water but that DI water was preferable. I don't have DI water but could I use RO water - how much difference would it make?

I also wonder whether there's any need to check it at all. I got it free with my TDS meter but I though it would be handy for checking mash PH - I used it last brewday and the reading was the same as predicted by bru'n water so I suppose I'm thinking that it's probably accurate. The instructions dont say anything about calibrating it before first use just after a lot of use or after a lot of no use.

 

[schokie]

I have a similar one. It works ok, but the calibration drift is pretty bad. Might not notice it if you used it all the time, but if you're just using it once a week or every other week it'll be off by at least 0.3. You must calibrated prior to each use. I ordered buffer solution off amazon. The amount that comes with it is only enough for one use.

You really don't want to use tap water. It's not going to have a ph of exactly 7.00 and its residual alkalinity will throw off the buffer solutions, giving you invalid calibration points. Distilled water is really easy to find. I bought a gallon of it at the local grocery store in the bottled water section. That's lasted me a long time.

Tip for this meter: let it soak in distilled water for at least 5 mins, longer is better. Otherwise your readings will be jumping all over the place. The long soak gets the readings to settle out right away.