Salinity expansion problem

[AndyC]

I have the salinity expansion and calibrated it in the tank (verified with a refractometer) but then it shows the salinity dropping by about a point per day down into the teens. The probe looks ok, no precipitate as far as I can tell. What might be going wrong? Is there a way to clean the probe, or is the probe faulty? It's been doing this since about 1-2 weeks after installation.

[rimai]

You can clean it by soaking in white vinegar.
What happens if you drop the probe in a cup with tank water?
Was it working correctly in the first 1-2 weeks?

[AndyC]

It's hard to say if it was working properly. I tried calibrating in refractometer calibration solution and couldn't get it to match once I put the probe in the tank. It would be 35 in the solution and 30 in the tank. I messed with it for a while and then just figured I'd just make sure it stayed around 30 and then I'd be good. Then it started dropping from there.

I'll try cleaning it and see if that helps. Hmong often should the probe be cleaned?

[wolffman64]

I also have the salinity expansion, and have a similar problem. My salinity goes way up and then keeps on dropping, and I could also feel some stray voltage in my sump last night (have never felt it before), but it was gone this morning, but the salinity probe is still going haywire.....

[Paul_Velasco]

I have to say I am seeing the same thing. Cross calibrate with 35 ppt solution and hanna photometer. It should be dead on 35.

The issue is micro bubbles. If I shake the meter it goes back to 35. Throughout the day it will drift down into twenties. Once I shake probe and get rid of bubbles back to 35. So check for bubbles even if you think you have none. I am going to fabricate a sensor holder and put probes directly in tank. Hopefully reducing the bubble issues. The sump does not seem to be the best placement for my sensors

[Paul_Velasco]

Changing the probe to the overflow and it is dead on 35 all day

[AndyC]

I had the probe working for several months but now it's frozen at 6.0. I unplugged it, unplugged the whole unit, etc, recalibrated and nothing helps. When I try to recalibrate, if just shows 0. I've had it six months. It can't be worn out already, can it?

[rimai]

Try cleaning it.
If you have stray voltage coming from somewhere, it could deteriorate the probe faster.

[AndyC]

I did clean it in white vinegar and nothing changed. There shouldn't be stray voltage anywhere. I have a ground probe going. How long are probes supposed to last?

[rimai]

I would say for at least a year. I've used mine for a couple years now.
The manufacturer says with good cleaning practices, it lasts for a couple years or more, but their cleaning practices involve some weird solution, which I know nobody will ever do.

[AndyC]

should I contact the manufacturer or is there a warranty on them? The unit itself looks fine, no corrosion. Just dead.

[rimai]

PM me for RMA and we go from there.