Conductivity Probe Calibration?

[tomreefer]

I have the 2016 APEX and I was told to do it this way:

Dry probe about 2hrs out of tank
Put tank temp at 77 degrees
Let calibration solution float in tank for 30 min
Do manual calibration
Set TC at 2.2 Update apex
Now start manual calibration
Wait about 2 min to settle (dry)
Put probe in solution(In sump) tap on probe to release bubbles
wait at least 5 min
after that probe should be calibrated..

This correct?

 

[ohashimz]

Yes but you over complicating a bit.
I will assume here that you have s yemp prob in the tank connected to apex
No need to change tank temp, as long ad you make the solution similar to tank temp(hence you put the solution bag in the sump to have it the same temp) you should be good. Because the prob use the temp from the prob to adjust the reading based on temp change.
Also no need for 2 hours to dry the prob, I dry it using a towel without too much rubbing, then leave it for like 10 20min while the calibration solution in the sump then I calibrate.

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[tomreefer]

Ok finally got my probe working.. Showing 34.9ppt and my Milwaukee showing 35ppt.. I am guessing my Milwaukee off a bit.

 

[ohashimz]

Ok finally got my probe working.. Showing 34.9ppt and my Milwaukee showing 35ppt.. I am guessing my Milwaukee off a bit.

Naah. Your apex is bit off and that's the best you can get. It will actually drift over time more s bit but I would donot care. You cannot use apex prob as your main salinity check, they are not that accurate. Use it to show you a trend or big event that's all.

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[tomreefer]

Yea I have an alarm if Salt goes less than 32ppt or shut off my ATO.. Or that not good to do?

 

[ohashimz]

Yea I have an alarm if Salt goes less than 32ppt or shut off my ATO.. Or that not good to do?

That should be fine.
If you are looking at accuracy you need to use other devices like reflectometer or Milwaukee. Use apex prob with +-2ppt accuracy in mind. Do not believe anyone who tell you otherwise.

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[ohashimz]

One more thing. Make sure you have a temp prob connected to you pm2 module because the probe use the temp pulled by the same module its connected to...at least that how I remember once heared from neptune

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[tomreefer]

I have the APex 2016 model and no PM2..

I heard the TC factor is the issue and has to be played with. I have it set to 2.2. However, when changed value it does nothing lol.. unless that is based off temp because my temp is 77 degrees and constant

 

[RussM]

Naah. Your apex is bit off and that's the best you can get.

The published resolution and accuracy of the Milwaukee MA887 is 1.0 PPT and +/-2.0 PPT respectively. Therefore, there is no valid basis for your saying that the Apex is off. Likewise, there is no reason here for the OP to suspect that his Milwaukee is not correct.



The 0.1 PPT difference between the OP's Milwaukee and his Apex salinity probe is inconsequential; for all practical intents and purpose, the two measurements are the same.

 

[ohashimz]

The published resolution and accuracy of the Milwaukee MA887 is 1.0 PPT and +/-2.0 PPT respectively. Therefore, there is no valid basis for your saying that the Apex is off. Likewise, there is no reason here for the OP to suspect that his Milwaukee is not correct.



The 0.1 PPT difference between the OP's Milwaukee and his Apex salinity probe is inconsequential; for all practical intents and purpose, the two measurements are the same.

I am referring to a calibrated Milwaukee. When using the Milwaukee or reflectometer qe calibrate. But apex not ad much so it drift.
I was trying to explain the right expectation instead of just blindly advocating to the apex.
Basically I was avoiding the good old argument of" but then other side is bad as well".
I use reflectometer and calibrate it every time before use. That's the best way.
Apex prob is not good absolut measurment way, it's a good relative measurment.


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[kurt_n]

I think you're missing the point Russ was trying to make. No one is advocating one over the other.

Even if everything is perfectly calibrated, the published resolution and accuracy figures have to do with the electronics and software behind the numbers the display is telling you. With perfect calibration, if the readings between the Apex and Milwaukee units are less than +/- 2 ppt from each other, that is within their stated accuracies and should be considered equal.

For example, if my thermometer had an accuracy of +/- 2 deg F, and I was reading 80 deg F but I knew for certain it was actually in 82 deg F water... that would still be within the accuracy of the thermometer. The thermometer is not "wrong" or "inaccurate" at all... it's just doing the best it can.

 

[ohashimz]

I think you're missing the point Russ was trying to make. No one is advocating one over the other.



Even if everything is perfectly calibrated, the published resolution and accuracy figures have to do with the electronics and software behind the numbers the display is telling you. With perfect calibration, if the readings between the Apex and Milwaukee units are less than +/- 2 ppt from each other, that is within their stated accuracies and should be considered equal.



For example, if my thermometer had an accuracy of +/- 2 deg F, and I was reading 80 deg F but I knew for certain it was actually in 82 deg F water... that would still be within the accuracy of the thermometer. The thermometer is not "wrong" or "inaccurate" at all... it's just doing the best it can.

I get that, my point was, this prob will not hold its accuracy for more than a week after calibrated...while reflectometer or Milwaukee hold their performance for much longer.

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[ohashimz]

Here is my 4 months old apex salinity prob.
I kid you not I have got 6 thus far over 3 years on 2 seprate setups. The 35ppt point is the day I calibrated the prob.

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[vhuang168]

And here is mine with Temp overlayed. Does not drift over time.