milwaukee pH controller, incorrect readings

[jankyjameson]

if someone could help me out with this it would be greatly appreciated. i have a milwaukee sms122 pH monitor in my tank, and i am getting inaccurate readings. i calibrated it straight out of the box with the pH 7.01 solution, and it stabilized at 7.01 like it was supposed to. when i put it in my tank, it got a reading of 7.5, and have gotten btw this and 7.6 for the last 2 weeks, though several other tests say otherwise. elos and api tests read a pH of 8.2.

i am not sure that the probe i have is the one that was supposed to come with the monitor, because it has a screw on type cap that would fit into a calcium reactor. none of the probes/electrodes that i have seen on their website have this, and it seems to be permanently attached to mine. and given the situation that i got this monitor, it is possible that the probe could've gotten switched b/c it was an open box buy. does anyone know if the electrode that comes with the 122 is supposed to have this? it doesn't seem unreasonable because it is meant to be a controller, i'm just not using it as such. anyone have any idea what the problem could be/why i'm getting incorrect readings? i read somewhere that i needed to get the 10.1 solution as well and use both, but the milwaukee website says otherwise so i just don't know. please help.

 

[Randy Holmes-Farley]

Does it have 2 point calibration? Setting pH 7 alone is not adequate.

If it only has single point calibration, which may mot even be usable if it cannot read pH 10 correctly, you need to at least check it in pH 10 solution to see how far off it is.

Any pH probe that actually fits the connection will work for any meter.

These articles have more:

Measuring pH with a Meter
http://www.advancedaquarist.com/issues/feb2004/chem.htm

A Comparison of pH Calibration Buffers
http://reefkeeping.com/issues/2005-02/rhf/index.htm

 

[jankyjameson]

perfect. i appreciate the help, and thanks for the quick response.

 

[Randy Holmes-Farley]

You're welcome.

Good luck.

 

[madadi]

it doesn't sound like it is the factory probe. even though any standard pH probe should work, i would be concerned since its a returned item. maybe someone wanted to get a free probe and decided to return it with their old, not working probe. see if you can borrow a working probe from a friend and see if you get a better reading.

i have the same controller and i love mine. it was calibrated out of the box. i put it in 7 it read 7, i put it in 10 it read 10. i put it in my tank it read 8.2 borrow a good probe.