Help? Defective pH probe?

[fishnu]

OK, trying to calibrate my new ac3 pH and either I am doing it wrong or I have a defective probe.

I removed the clear latex cover ( I assumed I should since it was airtight)
I placed the probe in my tank

It read over 12.

So I got some rodi water and some calibration solution (7 and 10)

I went to setup>ph calibration>ph>7.0 calibration
I dipped the probe in rodi water for 10 seconds, wiped it off, placed it in the 7.0 solution, and waited.
No change...12.73
Finally I hit select, selected 10, rinsed the probe in rodi, placed it in the 10 solution and waited............................................ .................................................. .................................................. .....................12.73

OK, I hit select............................................ .................................................. .................................................. ..........Defective probe.

Am I doing something wrong or is the probe defective?

John

[Mako]

Is this for the AC3 Pro? I know with the Pro you need to have the temp probe in the solution with the ph probe when calibrating. Something to do with a ground reference if I am not mistaken.

Not sure if this is the same for the AC3 also. I know it surprised me as you did not have to do that with the any of the AC2's I owned.

[broke1]

I think I may be having a problem that's along the same lines. When I calibrated with the 7.0 solution, the AC3 read 7.93, when calibrating with the 10.0 it read 11.03. Now that it's back in the tank it says 6.41.

Is that true about having to have the temp probe in the solution? That I did not do.

[kenargo]

When you calibrate, the reading that you see in the screen (during the calibration) does not represent the PH of the solution; it is just a reading which the AC uses to create the reference and slope values for the particular probe. Once the calibration is completed you can 'double check' that the calibration was successful by placing the probe into the calibration solutions and you should get the correct readings. If the probe reads correctly then when placed in the tank it is most likely a correct reading.

Note: If the calibration fluid is bad or contaminated then it is possible that the calibration could be incorrect and therefor the readings would be incorrect but I haven't heard of this being common.

ONLY for the AC3 Pro does the temp probe need to be in the solution. The AC3 Pro has slightly different electronics and uses the temperature probe as a ground reference for the PH (and ORP) probes. The AC3 and AC3 Jr does not require the temp probe to be in the PH solution.

[svb57]

Hey kenargo

I too was tryign to calibrate pH probe and had same issues as fishnu. Read your post and was able to calibrate....

Thanks
Jim Mc

[fishnu]

My Probe is defective. I shorted the pH socket and it went to 7. I plugged the probe back in and it went back to 12.7. I placed the pH into the ORP socket and it read 0.0

So, good AC3, bad probe.

Anyone got a probe to sell cheap??

[60Cubed]

I had a bad probe brand new. It would calibrate, then start to drift lower and lower. I replaced it with a brand new pinpoint and it works perfectly. I sent it back and they sent me a new one. Just got it in the mail. There is a warranty on the probes. But I think the pinpoints are a better probe. JMO though. I will keep the pinpoint on my tank and use the neptune on my reactors. The accuracy on them isn't as crucial.