What is an acceptable margin of error for Apex brain/PM1 pH readings?

[smartwater101]

I had a heck of a time getting my (brand new) Neptune probe calibrated. I had to send it in for "diagnostics and repair." While waiting, I purchased a Milwaukee probe and BRS probe.

Once the Neptune probe was returned I tried all 3 and all 3 calibrated well. But would eventually drift within the week. Placing any of the probes in 7/10 solution (for at least 5 min) would show o .06 - .1 off.

Same goes for the Alkatronic that I now have plugged into PM1. While calibrating, Apex would read 10 and 6.99. Now .01 inaccuracy is reasonable in my opinion. But just a few days later it will start to drift. Alkatronic reading 9.45 and Apex displaying 9.51. Seems crazy since Apex isn't reading a probe in this instance.

Is an offset of .06 -.1 common? Since its happening with 4 different probes and 2 different modules, I'm wondering, what should my expectations be for these readings? Seems a bit much to me. Certainly not giving consistent readings anyway.

Thoughts?

 

[Brew12]

I had a heck of a time getting my (brand new) Neptune probe calibrated. I had to send it in for "diagnostics and repair." While waiting, I purchased a Milwaukee probe and BRS probe.

Once the Neptune probe was returned I tried all 3 and all 3 calibrated well. But would eventually drift within the week. Placing any of the probes in 7/10 solution (for at least 5 min) would show o .06 - .1 off.

Same goes for the Alkatronic that I now have plugged into PM1. While calibrating, Apex would read 10 and 6.99. Now .01 inaccuracy is reasonable in my opinion. But just a few days later it will start to drift. Alkatronic reading 9.45 and Apex displaying 9.51. Seems crazy since Apex isn't reading a probe in this instance.

Is an offset of .06 -.1 common? Since its happening with 4 different probes and 2 different modules, I'm wondering, what should my expectations be for these readings? Seems a bit much to me. Certainly not giving consistent readings anyway.

Thoughts?

I wouldn't think so. I don't have an Apex any longer but my pH probe will stay within 0.02 for at least a few months between calibrations. It sounds like your Apex has an issue with the sensing circuit but I'm not sure what their tolerances are. I would reach out to Neptune and ask if what you are seeing is within their design criteria.

 

[BestMomEver]

My husband is the quality manager at a large chemical manufacturer. They use pH probes daily (he’s a chemist). He tells me they calibrate them with EVERY use. And they are the high quality, lab grade units. He believes that a pH probe will become less and less accurate with every use, making a continuous use probe (like Apex) not very accurate at all. I guess it depends on what margin of error you’re willing to accept, but I don’t put much faith in mine. I measure dkh daily. It’s a better indication of tank health, IMO.

 

[ca1ore]

I tend to be happy with accuracy of 0.1 plus or minus. Partly why I don't like the idea at all of using a pH probe to control anything. Monitor/alert …. yes; control …. absolutely not.

 

[smartwater101]

Contacted Neptune and the response was "how long did you wait for a reading." Apparently the 10 min I mentioned in the email wasn't clear lol.
They haven't responded in 2 days. le sigh...