pH controller questions

[jrp1588]

I bought one of those Milwaukee 122 pH controllers and am having some minor problems. Something in the calibration isn't working properly. I can calibrate it to 7 with the supplied 7.01 pH solution, but when I dip into the 4 pH solution, i can only dial it in to 5.1. I followed the instructions to a T. Is my calibration fluid bad? Could it have been contaminated? I did try testing some of the 7 pH calibration fluid with my test kit and registered at barely over 6...I'm not sure if it would work though, is the calibration solution simply water buffered to the specific pH?

My other thought was that maybe my probe is bad. Instructions said it was supposed to have a cap on it which was supposed to be removed while in use...the cap is simply to protect the probe. Well, there was no cap. What do you think would be the most likely issue? Also, where would I buy replacement calibration fluid and probes? I can't find a website for Milwaukee.

 

[neilanh]

I would suspect the probe as well. Where did you purchase the unit?

Here's one place to buy probes, but if you just got the unit I'd talk to them and get them to send you a replacement.

 

[jrp1588]

I bought it used, so yeah, no kind of guarantee or anything.