Conductivity Probe Calibration Problem

[shardyl]

Hi

I just calibrated my conductivity probe using the 50ms solution.

All went well but when i put it back in the solution at the same temp as the tank, I got a 49ms reading. I thought that was quite close but decided to calibrate again to see if i could get it more accurate.

I followed the same procedure again (but it had been in rodi water for about 5 mins) and this time the solution read 32.9ms!

I did it one more time and it still read 32.9ms. (wish i had left it alone!)

What have i done wrong? and how can i fix this problem?

thanks

[GHL Support]

You should simply repeat the calibration procedure.

[shardyl]

I have repeated the calibration process 4 times now and the reading of the fluid still comes out at 32.9-32.8

I have now ran out of calibration fluid.

could the probe be defective?

[GHL Support]

The first calibration went ok, didn't it?

Did you change anything before the second try?
Could you post the ADC (ADC1 / ADC2) values for the conductivity probe reported in ProfiLuxControl?
If you are using salt water with a ProfiLux3eX or ProfiLuxPlus2eX the range should set to salt water. If ProfiLuxControl shows Conductivity(S), the range setting seems ok.

[shardyl]

Yes the first one came out at 49 with the probe in the solution after the calibration

I left the probe in ro water and tried again

the ADC values were pretty constant during calibration with ADC1 at 19-20 and ADC2 at 449-451

The probe is set to sea water in profilux 3ex

[GHL Support]

Hm, the ADC values seems good - the higer value is perhaps a little low - but I have no reverence value now.

Which firmware version is running and which model do you have?
Did you a firmware update?

Maybe a solution:
save your settings and sensor data via PLC
make a factory reset on your ProfiLux
load the settings to the ProfiLux via PLC
check the ProfiLux settings
retry the calibration (you could reuse the calibration fluid for those tests - if the calibration went ok you could repeat it with fresh calibration fluid)

[diverdutch]

When did you purchase the calibration fluid? as in nov/dec there was a falty batch of mS liquid...
Forward the barcode of the bottle to GHL for checking!

[Matthias]

I doubt that the calibration fluid is the problem - we had a few bottles with 1.4mS in it instead of 50mS, if this would be the case he would measure complete different values, but these values are nearly OK

the influence of the temperature compensation is very high for conductivity measurement, that means that the temperature of the calibration fluid must be entered very accurately

just for testing - to check the probe and hardware with eliminating the temperature influence you can do this:
calibrate and enter a fix temperature, e.g. 25°C, and set a fixed temperature for the compensation instead of using the temperature probe
-> after this the ProfiLux should show a reading of 49.8 ... 50.2 mS when immersing the probe into the calibration fluid right after the calibration process

[aqua_digital]

This thread maybe of some help, not entirely related but could help others with issues and expectations

http://www.reefcentral.com/forums/showthread.php?t=1946686&highlight=salinity

[akindbro4u]

I'm having the same problem. Readings of 32.8 after calibration.

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[shardyl]

Just wanted to add that this problem was me being a total dumb ass!

You have probably got your reading set to the wrong type of measurement. i cant remember off hand what it was but when i changed the measurement reading type it turned out the probe was calibrated correctly!

doh!

[akindbro4u]

Fixed it. Very odd. Switch from salt, to fresh, and back. Now it works.

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