Apex Conductivity probe not stable!

[BlackTip]

I installed the Apex conductivity probe 3 weeks ago. I installed it and calibrated it per instructions. The initial reading was off by 1 full point, but the reading was somewhat stable. The reading was between 31.5 - 32.1. My Milwaukee refractometer reads 32.

In the past two days, the reading fluctuate too much. It goes to 32.5, then withing ours drops to 29. I relocated the probe from between the baffle to the return section. Again, it went up to 32+ then drops to 29. It keeps doing this.

Is this probe faulty?

I have my outlets programmed to when the reading goes below 31. Yesterday, I had warning, alarm, text and email going off. I had to go home in the middle of work day to make sure everything is OK, and I woke up in the middle of the night on the alarm sound. I took the programming code out for now.

 

[slief]

You either don't have it calibrated properly or didn't let it settle in long enough before calibrating. FWIW, they should be in the water for about a week and then recalibrated for best accuracy. Also, when you calibrate, you should have the temp probe associated with the conductivity probe in the calibration solution so that temperature compensation is accurate. You also need to allow the probe plenty of time to settle during the calibration process and swirl the probe in the solution so that there are no air bubbles trapped in the probe tip.

You may have it in a heavily aerated area of your sump which can cause the Conductivity to be lower than expected.

Your Conductivity could actually be about 29. Have you measured your salinity with a properly calibrated refractometer?

Lastly, what is the salinity of your water when measured with a calibrated refractometer? FWIW, you should always calibrate your refractometers with 1.026 calibration solution and not distilled water.

Lastly, if you have stray voltage in your tank and or have the probes wires running parallel to any power cables, that can cause interference with the probe and instability in the readings.

All said, if I had to guess, you didn't allow the probe to settle in long enough in the tanks water before you calibrated it and likely need to recalibrate the probe. That or your salinity in your tank is lower than you think.

 

[BlackTip]

I calibrated the probe per instructions. It is connected to PM2 and the Temp probe is also connected to the PM2. It is configured to read salinity. That was 3 weeks ago. I didn't re-calibrate, because I don't have extra solution as of now.

My brand new and calibrated Milwaukee refractometer reads 32 each time.

All of my probes were located between the baffle, and they were fine. After the fluctuation of the Conductivity probe, I moved all of the probes to the return section. Water is very clam and stable there.

I thought of stray voltage, but I didn't add any addition equipment since then. The heaters are not even on.

Here is the chart for the today:

 

[Jyetman]

Don't forget to tilt the probe at a 45 degree angle. This helped fix mine.

 

[karimwassef]

I have one so I sympathize.

These probes are very sensitive to bubbles and particles. You need to find a quiet place where particles and bubbles are non-existent.

Make sure it's clean and 100% dry during the dry-cal portion. Make sure there are no bubbles during the wet-cal.

Finally, mine was susceptible to electrical interference. Look at the wires next to the probe wire. Do you have a powerhead wire? Heater wire?

You'll need to play around to reduce the noise.

In my case, I basically accept the variation as long as it's generally between two known states. I use it to look for big things, not fine measurement.

 

[slief]

I calibrated the probe per instructions. It is connected to PM2 and the Temp probe is also connected to the PM2. It is configured to read salinity. That was 3 weeks ago. I didn't re-calibrate, because I don't have extra solution as of now.

My brand new and calibrated Milwaukee refractometer reads 32 each time.

All of my probes were located between the baffle, and they were fine. After the fluctuation of the Conductivity probe, I moved all of the probes to the return section. Water is very clam and stable there.

I thought of stray voltage, but I didn't add any addition equipment since then. The heaters are not even on.

Here is the chart for the today:

To me it looks like your temp compensation is off or you didn't calibrate salinity with the temp probe in the solution or the calibration solution was different than the tank temp. I assume you have a second temp probe connected to the PM2? If not, did you assign the primary temp probe to the CondX probe for temperature compensation?

Can you post a graph for both temp and CondX? There is likely some correlation between that and Conductivity. The swing from 29 to 32 is a big swing. I'd expect to see swings of around .2 to maybe .4 which isn't enough to show up on a refractometer but 29-32 is a pretty big swing. That leads me to believe it's temperature related or something else in the tank that turns on and off at certain intervals like a DC pump, power head etc that could be producing stray voltage.

 

[BlackTip]

I have only one temp probe. It is assigned to the conductivity probe. The temp compensation is 2.2. When I calibrated, I didn't have the temp probe in the solution, but I had the solution bag in the same water.

My temp probe started to act up as will. Temp started climbing for no reason. I tested with 3 other thermometers and the reading were: 80F, 80F, 79F, but the probe reads 80.8

 

[slief]

Have you updated the firmware on your PM2? You might want to do that and then recalibrate. You don't have a temp probe on your base unit? Only on the PM2? If so, you should be able to move the temp probe to the base unit and select that temp probe as the one for the PM2. I'm asking that because TempX5 is the same name my PM2 temp probe uses where as my base temp probe is called "temp"

 

[BlackTip]

Have you updated the firmware on your PM2? You might want to do that and then recalibrate. You don't have a temp probe on your base unit? Only on the PM2? If so, you should be able to move the temp probe to the base unit and select that temp probe as the one for the PM2. I'm asking that because TempX5 is the same name my PM2 temp probe uses where as my base temp probe is called "temp"

When I was installing them, in the BRS video and the intruction manual, they strongly advice to have the Temp probe plugged into the PM2. They said, it will be more accurate this way.

I am going to order calibration solution and do it over.

BTW, what is the best place in the sump to place the probes?

 

[slief]

When I was installing them, in the BRS video and the intruction manual, they strongly advice to have the Temp probe plugged into the PM2. They said, it will be more accurate this way.

I am going to order calibration solution and do it over.

BTW, what is the best place in the sump to place the probes?

A place of high flow with minimal light and ideally, no micro bubbles. That said, the drops in your graphs make me suspicious (29-32 Salinity). That's equivalent of going from 1.021 to 1.0236. Something isn't right and there also seems to be a pattern to the salinity drops and peaks in your graphs. That said, from 14:00 on, it seems to have flatlined at 32 (salinity).

Not sure about the validity to what BRS mentioned in their video. I run separate temp probes and as part of my redundancy.

 

[jason2459]

Yes you can't use the temp prob for the conductivity from any other input. It has to be in the pm2 to work with the conductivity probe.

You need to have the temp probe in the same solution during calibration. You have to make sure they are well rinsed and completely dry before calibration.

Make sure the temp probe is next to the conductivity probe in the sump/tank. You can adjust the compensation up or down as needed.

Your return pump could be the main issue. There's a lot that can interfere with a conductivity probe or any probe for that mater.

 

[jason2459]

Also I would suggest the Neptune 53mS solution. Not another brand. Yes, they are different. No, you will not be able to calibrate a refractometer with it as it is does not have a salinity of 35ppt.

 

[BlackTip]

I filed a ticket with Apex, and they responded by saying that I need to re-calibrate and move the temp probe from the PM2 to the main module with 0.0 compensation.

The manual, however, states the following:

" In order for the PM2 to automatically compensate for changes in conductivity as the temperature
of the water changes, you must connect a temperature probe to the PM2 and set the temperature
compensation as described below. The temperature probe connected to the Apex Base Module cannot be
used for automatic temperature compensation on the PM2."

 

[jason2459]

I filed a ticket with Apex, and they responded by saying that I need to re-calibrate and move the temp probe from the PM2 to the main module with 0.0 compensation.

The manual, however, states the following:

" In order for the PM2 to automatically compensate for changes in conductivity as the temperature
of the water changes, you must connect a temperature probe to the PM2 and set the temperature
compensation as described below. The temperature probe connected to the Apex Base Module cannot be
used for automatic temperature compensation on the PM2."

Would be interested in clarification on their suggestion. My understanding as well is that would not allow for any ATC with the conductivity probe.

 

[BlackTip]

Would be interested in clarification on their suggestion. My understanding as well is that would not allow for any ATC with the conductivity probe.

I responded to their email, and asked for clarification already.

 

[BlackTip]

Have you updated the firmware on your PM2? You might want to do that and then recalibrate. You don't have a temp probe on your base unit? Only on the PM2? If so, you should be able to move the temp probe to the base unit and select that temp probe as the one for the PM2. I'm asking that because TempX5 is the same name my PM2 temp probe uses where as my base temp probe is called "temp"

I have only one temp probe. I updated the firmware 3 weeks ago.

The funny thing is that everything was working fine for 2 weeks, before it went crazy.

The Conductivity probe reading has been stable since yesterday.

 

[jason2459]

I have only one temp probe. I updated the firmware 3 weeks ago.

The funny thing is that everything was working fine for 2 weeks, before it went crazy.

The Conductivity probe reading has been stable since yesterday.

Nice. Could be many things that will cause it to swing around. Also, having it in your return section or the baffles just before it could also be thrown off by anything at all you might be dosing or like stated above any kind of microbubbles produced by various things like the skimmer, drains, turbulence going over/through the baffles, etc.

I've always had my probes in the least turbulent area, with as little light as possible or none at all hitting them, and upstream from any kind of dosing. Even ATO of fresh water will through it off. Lime water top off even worse.

I would still get another temp probe in another section just as a check and balance like slief said above as well. I've some how gone way overkill on temp probes and probes in general.

Behind my display tank I have an external overflow for my beananimal. No light directly hitting it and in the corner of it there's very little turbulence. I have there a temp probe, pH probe, and ORP probe.

In the drain section of my sump in the opposite corner of where the drains are is low turbulence, upstream from any dosing (I do vinegar and kalk top off), and I do not have it lit. I have there a ranco temp probe and then the apex temp, conductivity, and another pH probe. I also have a temp thermometer stuck on the inside I can read through the glass. I also have my old reefkeeper temp/pH/conductivity probes still in there as I just switched over to the apex.

I cross check all those. They are all with in hundredths or tenths of degrees of each other and so far fairly stable minus when I screw with them.

 

[BlackTip]

I may have to design something. There is no place in the sump that meet all of the criteria (no micro bubbles, low flow, low light). I have 5 sections in my sump - drain, skimmer, gfo/carb reactor, return, and fuge. The calmest section is the fuge, but it is let at night. The second suitable section is the return section. That were the probes located right now. Previously, they were located in between the baffles right before the return section. There is high flow area.

 

[jason2459]

I'd put it in the drain section in a corner away from equipment and drain if possible. You could also create pvc probe well(s) for them. Google search aquarium pvc probe well. Lots of DIY mods out there.

 

[jason2459]

Also, to clarify when I mentioned my readings have been stable is that they vary in a dependable and expected pattern with in a target range. If my readings don't change through out the day I think something is wrong.