Calibrated PH probe(s) read diff. #'s in the same rez.Why?

[Thallamus]

Ok here’s a little brain teaser (at least it is for me). I have a Hanna Grochek Combo ph/ec/tds/temp meter. I recently had to get a new ph probe for it because the first one was damaged in shipping. So I had to get a milwaukee ph stick until the new probe came in. After the new Hanna probe came in, I decided to see how different the ph calcs were (Milwaukee vs Hanna). After calibration, both read the buffers (7.01 and 4.01) correctly. Now here is the really weird part. When I use both probes in my rez, I get large differences between the two. Example, the Milwaukee will read 6.3 and the Hanna 5.2. Am I missing something here? Any help would be appreciated. I am at week 4 and I don’t want my girls to lock out.
-T

 

[LBZ Farmer]

Are they both Temperature Compensating? That is important.

 

[Thallamus]

The hanna has two probes. One for Ph and the other for ec/ temp . The other probe (milwaukee stick) just measures Ph. I know the temp of the rez can play a part in measuring Ph. I think that's why the hanna is doing what it's doing. But the readings between the hanna and the milwaukee are so far apart. I'm not sure which number to go with so I just take the average reading. I don't want to keep doing things this way.
-T

 

[cemchris]

I would trust Milwaukee over Hanna anyday.