pH probe problem?

[Dave_P]

I have had my probes almost a year now.

The other day I recalibrated one of the probes using 7 & 10 calibration fluid. The calibration went fine.

Although now the probe seems to be reading approx .2 under what it should be. Prior to the calibration the probe was reading fine.

Now I know what you are thinking ;) but no it is under reading when compared to another pH probe + interface (brand new) and a handheld pH meter.

Is this indicating that the probe is coming to the end of it's life?

Dave

[Dave_P]

Same thing has happened to my calcium reactor probe :mad: which I calibrated at the same time

Dave

[Dave_P]

Just went to calibrate again, after using the ph10 calibration fluid I am getting 'Bus Error' :mad:

Dave

[Dave_P]

After a lot of playing, when I calibrated the probes, I did it through the PC software. The probes are then out! If I do it through the controller I get a 'Bus Error'. I am guessing that the PC software is ignoring the Bus error and calibrating incorrectly.

I have changed the controller (bought as a spare the other day) and that didn't make a difference. I have changed the probe (again new) and still got the bus error. That only leaves a problem with the ph interface or power bar. I am guessing the pH interface.

Dave

[jobr]

Seems very strange dave, I had trouble calibrating a probe after just over a year, so i replaced it and all was well.

Not heard of any other problems with the interfaces.

Have you PM'd Ian?

[petergillett]

Been fighting with my year old probe. Calibrated fine each time but reported tank at 7.5 ish. Struggling to get good effluent without pushing to 6.3 (as Dave already knows from earlier discussions).

Bought a new one the other day from a non sponsor, all looking good now.

Tis a bit of a concern if they calibrate and then read wrong. How are you supposed to know they're duff and ready for changing? (Without buying another to compare with and being 100% sure it's calibrated correctly!)

[muzzy]

as a side note,
i read a good article the other day on calibration fluids. seemed that the only one worth getting that is easily available to us is the pinpoint solutions.

there were massive fluctuiations in many of the ph solutions they tested.

http://www.reefkeeping.com/issues/2005-02/rhf/index.php

[Dave_P]

Seems very strange dave, I had trouble calibrating a probe after just over a year, so i replaced it and all was well.

Not heard of any other problems with the interfaces.


When I initially got the system, I had to have one of the interfaces replaced as it wouldn't calibrate. This was after a replacement probe was sent.

So it's not unknown!

Dave

[Dave_P]

I noticed that there is a lot of difference between the speed of calibration between the old and new probes.

I am going to order 2 new probes and a new interface, as the probes are going to be due to be replaced soon anyway.

If the interface proves to be faulty, I will send it back under warranty.

Tis a bit of a concern if they calibrate and then read wrong. How are you supposed to know they're duff and ready for changing? (Without buying another to compare with and being 100% sure it's calibrated correctly!)

The only reason why I found out about the calcium probe is the fact that alkalinity dropped down to 7 dKH. Just coinsiding with a bulb change :mad:

Reviewing the chart it was obviously under reading from the calibration. I would post the chart, but I don't want to go through the hassle of setting up a new controller again, the data is on the other controller.

Dave

[petergillett]

On a side note re our other thread, with the new probe I'm now pushing 34dkh of crystal clear at 6.4ph at 50ml/min on the 1501 outputting from the CO2 bleed rather than the outlet.

[Dave_P]

On a side note re our other thread, with the new probe I'm now pushing 34dkh of crystal clear at 6.4ph at 50ml/min on the 1501 outputting from the CO2 bleed rather than the outlet.

That's pretty good :applause:

I am not too sure what I am at the moment, the last time I measured mine it was 47dKh at 46ml/min (from memory). But I have increased the flow since then.

Once I have the probe sorted, I will measure mine again.

But my pH is starting to drop because of the CO2.

Dave

[petergillett]

the last time I measured mine it was 47dKh at 46ml/min (from memory)

And I thought I'd done quite well getting my 34dkh at 50ml!

[Dave_P]

Told a lie :laugh: Looking at my records

41dKH at 48ml/min (it's more than this now)

41 * 48 = 1968
34 * 50 = 1700

So you are not too far behind me.

Considering I started at 50ml/min (probably high) at 28dKH, IIRC you started about here as well.

50 * 28 = 1400

Dave

[petergillett]

Definitely probe related. I was running mid 20s at 35ml until I really pushed the ph down 6.3 ish. Swapped the probe and 28dkh/50ml/6.5ph or 34/50/6.4

Would be useful if there was a real indicator to say they weren't working. Not to bad on a free probe that you can pull out and pop in calibration fluid, but getting the probe out of the 1501 is a bit of an effort.

[Dave_P]

My alkalinity had dropped, so I looked at the graphs.

I turn off the CO2 overnight and the pH rises in the Calcium Reactor. Looking at the graphs I could see that the pH was not rising overnight to as much as it should. The time it started coinsided with my recent calibration.

Dave

[petergillett]

My overnight was rising to 7.5 in the reactor, now hit 7.7 within 2 hours and 8.0 by calcium on time.

Yet calibrations on old probe worked absolutely fine and measured to within .1 ph of the required value during the calibration.

[Robbyg]

If your AQ pH probe is a year old then it's just about at the end of it's life.

[arrows]

seems strange how they all start playing up after one year i wonder :rolleyes:

[Dave_P]

If your AQ pH probe is a year old then it's just about at the end of it's life.

Spoke to Aquatronica today and they basically said the same.

Although I have finally got my ethernet module working :dance::dance:

There was an issue with a v4 ph interface conflicting with the ethernet module which was my problem.

So they did add that this could be faulty and causing the problems with the other probes/interfaces and not necessary the probes needing replacing.

I am about to test all the probes to see what happens.

Dave

[Dave_P]

Finally got the 'Bus Error' sorted.

First, replaced the old probes but this didn't make a difference. Calibration still gave me a bus error on the probes.

So I started swapping the interfaces with a new one I purchased.

With the problems with the ethernet module, I changed the v4.0 interface first. This didn't make a difference, still couldn't calibrate.
Then swapped another, and I was able to calibrate all the probes :dance:

Just to make it clear, the dodgy interface affected all calibration on all probes on the system.

Dave

[Robbyg]

Good too hear :)
What Ver pH interface are you using now?

[Dave_P]

v7, v7 and v4. IIRC is was V6 which was the problem, although it had worked fine for ages.

Might have been due to the recent update, on the other hand might be coincidence. as it was only detected during a calibration after the update.

Dave