Apex conductivity probe

[dacostas]

So I bought a new apex and received it earlier this month. I've had nothing but trouble with the conductivity probe ever since.. It reads just under 32 ppt and I have contacted Neptune about this. After some back and fourth they told me:

"You calibrated it with solution it read 34.9~ this is normal. Broken probes would not read this well if they were non operational. Then placing it into your sump you get lower salinity. The probe is going to read what it gets based on the distribution of ions in the water it's sitting in. You cannot compare it's reading to anything else. Nothing with read number to number to our probe. Than after seeing this low number you moved it back to the bag of solution and it read 34~ again.

The probe is working as intended. The probe reading 31 in the sump is normal. As I mentioned. Our probe will not reflect values you see in refractometers or any test kits. It's a PPT reading of our own. It's operating normally."

I've tried everything from separating the probe from all wires, turning off All equipment minus apex, testing in a cup of tank water (so no flow, microbubbles, etc.), and if I add the probe in calibration solution it reads correctly. On 2 refractometers, they read 35ppt. My probe reads just under 32 in my sump and they say this is normal? It doesn't make sense why someone would be willing to spend so much $ on a system and one of the most important "levels" don't read properly? This is my first controller system so I have nothing to compare against but it doesn't seem right. I feel like I'm getting excuses by Neptune. I have tried every suggestion on forums for 2 weeks now and have recalibration a few times with a new calibration solution every time.

Thoughts? Suggestions? Thanks.

 

[reefeqmover]

Calibrate it in sump, easiest solution.

 

[Brew12]

So I bought a new apex and received it earlier this month. I've had nothing but trouble with the conductivity probe ever since.. It reads just under 32 ppt and I have contacted Neptune about this. After some back and fourth they told me:

"You calibrated it with solution it read 34.9~ this is normal. Broken probes would not read this well if they were non operational. Then placing it into your sump you get lower salinity. The probe is going to read what it gets based on the distribution of ions in the water it's sitting in. You cannot compare it's reading to anything else. Nothing with read number to number to our probe. Than after seeing this low number you moved it back to the bag of solution and it read 34~ again.

The probe is working as intended. The probe reading 31 in the sump is normal. As I mentioned. Our probe will not reflect values you see in refractometers or any test kits. It's a PPT reading of our own. It's operating normally."

I've tried everything from separating the probe from all wires, turning off All equipment minus apex, testing in a cup of tank water (so no flow, microbubbles, etc.), and if I add the probe in calibration solution it reads correctly. On 2 refractometers, they read 35ppt. My probe reads just under 32 in my sump and they say this is normal? It doesn't make sense why someone would be willing to spend so much $ on a system and one of the most important "levels" don't read properly? This is my first controller system so I have nothing to compare against but it doesn't seem right. I feel like I'm getting excuses by Neptune. I have tried every suggestion on forums for 2 weeks now and have recalibration a few times with a new calibration solution every time.

Thoughts? Suggestions? Thanks.

A refractometer and conductivity probe measure different things. A refractometer will indicate the total density of all the dissolved solids and how they change light flow through the water. A conductivity probe will only measure the dissolved solids that can conduct electricity. Since not all of the components of sea water are conductive I would expect the refractometer to read higher than the conductivity meter.

A good way to test this would be to dissolve table salt in RODI water to around 34ppt. Your refractometer and conductivity probe should read much closer since all of the dissolved solids should be conductive. If they still read substantially different during this test then I would question the accuracy of the probe further.

 

[dacostas]

A refractometer and conductivity probe measure different things. A refractometer will indicate the total density of all the dissolved solids and how they change light flow through the water. A conductivity probe will only measure the dissolved solids that can conduct electricity. Since not all of the components of sea water are conductive I would expect the refractometer to read higher than the conductivity meter.

A good way to test this would be to dissolve table salt in RODI water to around 34ppt. Your refractometer and conductivity probe should read much closer since all of the dissolved solids should be conductive. If they still read substantially different during this test then I would question the accuracy of the probe further.

Thank you for the suggestion. I tried your method using table sea salt (that's all I had) and both probe and the 2 refractometers I tested with came close. (34ppt vs 34.9)

 

[Brew12]

Thank you for the suggestion. I tried your method using table sea salt (that's all I had) and both probe and the 2 refractometers I tested with came close. (34ppt vs 34.9)

Glad to help. I think they would have been even closer with actual table salt. Others may argue, but I would use your refractometers to mix and check your saltwater. Use the probe to give you real time updates to make sure your salinity is remaining constant. Now that you know what to expect to see on the probe for a given salinity you will recognize if some unusual change is occurring.

 

[dacostas]

Glad to help. I think they would have been even closer with actual table salt. Others may argue, but I would use your refractometers to mix and check your saltwater. Use the probe to give you real time updates to make sure your salinity is remaining constant. Now that you know what to expect to see on the probe for a given salinity you will recognize if some unusual change is occurring.

Thank you! This was driving me up a wall and I feel confident in my probe now lol

 

[Brew12]

Thank you! This was driving me up a wall and I feel confident in my probe now lol

I will say that I find it disappointing that Neptune doesn't have a better way to explain why the probe reads lower. While their explanation about it being "based on the distribution of ions in the water" is accurate, it won't make sense to a large number of people. Instead of saying that "It's a PPT reading of our own" they should explain that the probe reads conductivity in micro siemens and they use a self created conversion factor to give an estimation in ppt based on that reading.
Just my feelings.

 

[WetWhistle]

Did you select temperature compensation when calibrating the probe? I had an issue like this but once i moved my temp probe from the base module to the PM2 salinity probe mine sits at 35 PPT no problem. Once my temp and salinity probe were on the same module with temp compensation checked off I had no issue. I know the salinity module is really sensitive to noise so if any cabling is touching the wires on it, it messes up my readings.

 

[dacostas]

I will say that I find it disappointing that Neptune doesn't have a better way to explain why the probe reads lower. While their explanation about it being "based on the distribution of ions in the water" is accurate, it won't make sense to a large number of people. Instead of saying that "It's a PPT reading of our own" they should explain that the probe reads conductivity in micro siemens and they use a self created conversion factor to give an estimation in ppt based on that reading.
Just my feelings.

Your reply makes a lot of sense. That's why I posted cause the "PPT reading of our own" statement just made it seem like they were just trying to close out another issue. Thanks again

 

[dacostas]

Did you select temperature compensation when calibrating the probe? I had an issue like this but once i moved my temp probe from the base module to the PM2 salinity probe mine sits at 35 PPT no problem. Once my temp and salinity probe were on the same module with temp compensation checked off I had no issue. I know the salinity module is really sensitive to noise so if any cabling is touching the wires on it, it messes up my readings.

I have the latest and it doesn't come with a pm2. I did try the compensation just in case and it did nothing at all. Now that I know it is working properly even though it's off by ~3ish ppt, I can trust it now and use it if an Ato fails, etc.. Thank you for the suggestion!

 

[andys]

I had a similar problem with apex. finely i called them for the 4th time very frustrated and the logged it to my computer and did the correct calibration and now both takes read the proper reading and they do match the same with my
Milwaukee

 

[cromag27 Verified Sponsor]

Can you expand on what they did?

@andys

 

[tomstrange]

Did you select temperature compensation when calibrating the probe? I had an issue like this but once i moved my temp probe from the base module to the PM2 salinity probe mine sits at 35 PPT no problem. Once my temp and salinity probe were on the same module with temp compensation checked off I had no issue. I know the salinity module is really sensitive to noise so if any cabling is touching the wires on it, it messes up my readings.

I was going to say... you need to either get another temp probe and plug it into the same module or move your temp probe to the same module. Otherwise, if you know that your water is correct going in the probe will just tell you if it varies. The temp probe needs to be plugged into the same module as the conductivity probe.

 

[Salty1962]

I bought an extra temp probe to put on my PM2 to help with accurate readings. That's what Neptune recommends, it's a bummer to have to purchase 2nd probe but at least I'll feel more comfortable with the readings.

 

[WetWhistle]

I have the latest and it doesn't come with a pm2. I did try the compensation just in case and it did nothing at all. Now that I know it is working properly even though it's off by ~3ish ppt, I can trust it now and use it if an Ato fails, etc.. Thank you for the suggestion!

I look at mine this way. Even if it doesn't show that actual value of my salinity as long as it shows a drastic change up or down in salinity I am good with that. If I need to know my actual level of salinity I will test it. At least it will show if something is wrong even if the salinity is not bang on. I use mine in the same situation as you for a fail in ATO ect.

 

[WetWhistle]

I bought an extra temp probe to put on my PM2 to help with accurate readings. That's what Neptune recommends, it's a bummer to have to purchase 2nd probe but at least I'll feel more comfortable with the readings.

I ended up doing the same thing. I just put one in my DT and one in my sump.

 

[dacostas]

I was going to say... you need to either get another temp probe and plug it into the same module or move your temp probe to the same module. Otherwise, if you know that your water is correct going in the probe will just tell you if it varies. The temp probe needs to be plugged into the same module as the conductivity probe.

It is hooked up to the same module (the control head unit) but with the new apex, it seems like I may need the pm2 for the compensation to work. I did try the temp compensation but it did absolutely nothing.