View Full Version : Can someone explain the "break in" period of a Salinity probe?

12/09/2016, 08:08 AM
I got my Apex set up the other day and calibrated the Salinity probe. When I put it in my water it was right on at ~35ppm, but shortly after it dropped to about 20ppm. After doing some research, I learned that these probes need a "break in" period, so I decided to leave it alone for a few days. Sure enough, all of a sudden yesterday the value started increasing. This morning it is now up to 30ppm. I'm expecting it to creep right back up to its accurate measurement...

But the scientist in me just needs to know how/why this occurs with these probes? Would someone mind explaining? Why would the correctly calibrated probe suddenly loose calibration significantly but then slowly creep back up?

Here's the graph:


12/10/2016, 11:56 AM
Sure enough, it's back at 35ppm

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12/11/2016, 03:37 PM
I have had this happen with pH probes also. It could be that films are on the probes from the manufacturing process that have to wear off of the probe surfaces. I always wait a few days after placing a new probe in the tank before calibration.

12/12/2016, 01:14 PM
also, if you start getting wack readings soak in vinegar

12/27/2016, 09:15 AM
So I had a horrible time with this probe over the last couple weeks. Finally, I realized that the probe gets air trapped in it that doesn't come out via the provided hole when you insert it into the water. So, I flipped the probe to the side under water and shook it vigorously. Sure enough, a bunch of bubbles came out. I then put it into the holder while still under water. Voila! The probe has now been dead-accurate and stable for almost a full 24 hours. I don't expect any issues from here on out.


They should make it clearer that simply inserting the probe into the water and tapping it is not enough to rid it of trapped air. It seems that you really have to put effort into getting it out.