Ph probe reads lower than my measured values.

[dradam]

Up and running after lightning destroyed my pentair automation system. Intellichem and easy touch boards are new as is my vf drive.

fc 4
ta 125
cya 30
ph measured 7.8
ch 250

Noticed the value from my PH probe was always reading about one entire unit lower than the intellichem reading. Measured 7.8 by strip and taylor test kit, but intellichem reads 6.8 with a .3 up tweak

Pentair tech just came out and replaced the PH probe yesterday , but the readings are identical. from the screen logic graph It almost looks like it is reading backwards-- yet the connections are correct. ph feed indicates 94 % activity, but the level is set to 7.5 and it is not dispensing muriatic acid.

F/C has been rock stable at an orp setting of 650.

While I have heard concerns about the intellichem usualy the concern is ORP and ph is ok. I would appreciate it if anyone has any suggestions as to why the ph reading and measured are so different.

Many thanks

 

[Bama Rambler]

Did they calibrate the pH to a standard solution?

 

[dradam]

No, They just changed the probe, came out when I was not there. I was disappointed that the did not schedule the appointment with me and look at the screen logic record as well. Had asked them to upgrade my intellichem software and while they said they would they did not do that either.

Thank you for responding.

 

[Patrick_B]

This seems strange to me. Isn't cal to a standard buffer the norm with these pool pH controllers? It certainly is in my business and we do three point cals to 4, 7, and 10. This way, the controller can set a reference curve so it can be accurate.

 

[Bama Rambler]

Any time a probe is changed out the new one should be calibrated. Preferably to 3 standards, but at least two.

 

[dradam]

the intellichem goes through its own calibration sequence on startup . Is that good enough ?

 

[Patrick_B]

Any time a probe is changed out the new one should be calibrated. Preferably to 3 standards, but at least two.

No different than ours that control acid/caustic feed, we just do it on a much different scale. There are units that don't require it, but guess what we think of them usually.

 

[Bama Rambler]

the intellichem goes through its own calibration sequence on startup . Is that good enough ?

I wouldn't think it's a proper calibration. The reason for calibrating to standard buffers is because each probes glass has a slightly different impedence and if you don't calibrate the electronics to that impedence, it can never know what the pH really is. There are probes that have electronics built into the probe that supply that info to the instrument but they're a little more expensive than you'd put on a pool.

 

[dradam]

Thank you,

I just got off the phone with the company that brought out the new probe. They are going to check it out again.

Many thanks

 

[Patrick_B]

There are probes that have electronics built into the probe that supply that info to the instrument but they're a little more expensive than you'd put on a pool.

:-D

You could say that.