PH meter calibration

[aztbs]

So I bought one of the Hanna digital PH meters because I have a hard time with the drops/color chart. I am having the hardest time with the calibration!
I had a powder and instructions to mix in 100ml of water. I bought distilled water and mixed up solutions. If I calibrate first to the 7.0 solution (which out of the box read 7.63), then the 10.0 solution reads 8.4! If I adjust the dial, it will not go up over 8.9. So I adjust to the 7 and then tried a 4.0 solution and it reads at 6.4 and will not adjust below 5.7.

So maybe I got bad buffer solutions? Could a low battery cause the reading to be off? Does anyone locally calibrate these things?

[Aaron]

if it is the low-end Hanna they are supposed to come already calibrated.

I have had 4 of those... they all ended up going bad and calibration became impossible!

I finally gave up, got my $ back and now I don't bother testing pH at all... and all is fine with the world :-)

[owsi]

What does it look like? Digital, with temp, red case with black cap, temp calibrated? They are self calibrating, if your are not sure about mixing the solution, buy the foil premix packets, get the 4.0 and the 10.0 for salt water, put in cal mode, put in 4.0 solution, when it says accept, shake off and dip in 10.0 till it accepts, thats all. then go back to 4.0 to check and 10.0 to check again. Store damp 4.0 or storage solution and should be fine for months if you take care of it. John