PH readings

Wbflyer · Feb 1, 2021

I have the Hanna PH checker and I just bought the Milwaukee Pro constant PH monitor. They both read the correct PH in the calibration fluid whoever, the Hanna is .3 lower than the Milwaukee. Hanna reads 7.7 and the Milwaukee reads 8.0. Ugh...

How could they be that off form each other??

lapin · Feb 1, 2021

You calibrated both with the same fluids and are you reading your tank water ph?

Wbflyer · Feb 1, 2021

lapin said:
You calibrated both with the same fluids and are you reading your tank water ph?

Yes, good question the same calibration fluid. The difference is when it's reading the tank water.

elysics · Feb 2, 2021

You keep referring to a singular calibration fluid, is that intentional or just a typo? There's supposed to be two different ones you use for calibration. Do they both read correct?

Wbflyer · Feb 2, 2021

Sorry, yes I used both the 7.01 & 4,01 for calibration

Randy Holmes-Farley · Feb 2, 2021

I don't know which, if either, is accurate, but check both again in the calibration fluids.

it would be pretty surprising if both read both fluids correctly, and still diverged that much in tank water.

Wbflyer · Feb 3, 2021

Checked them again in the cal fluid. Same results in the tank water. I guess I'll just take the middle of the two as the truth..

Randy Holmes-Farley · Feb 3, 2021

Wbflyer said:
Checked them again in the cal fluid. Same results in the tank water. I guess I'll just take the middle of the two as the truth..

So what you are saying is the both of them read each fluid correctly (the same 2 fluids) but then deviated only when read in the tank?

If true, I'd try them both in a cup of tank water away from the tank to see if one is experiencing electrical interference, which does happen.

The Pinpoint pH meter sometimes showed such issues if its electrical cord got near interfering devices, but had no such interference on a battery in the same location.

There are also things called ground loops that can mess with pH measurement, and the cup away from the tank eliminates that issue.

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