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MAKDENTAL
10.12.2011, 12:57
I'm sorry if this is covered elsewhere but I couldnt find reference to it:

I have just recalibrated my conductivity probe after cleaning in proprietary cleaning solution. I calibrated using GHL 50mS at 25 c and using "temperature probe1" (rather than Manual temperature) as the ref temperature in the tank turned down to 25 C as a temperary measure just to make it easier.

The strange thing is, at the end of calibration, the calibration program asks to save the new settings which I obviously do and at this point I havn't taken the probe out of the 50mS reference solution expecting it to keep reading 50 mS because its still at 25c, then over the next 20-30 seconds it climbs to 50.2mS. Surely it should still read 50mS? can some one please explain?

I repeated the proceedure to see what happened and got the same deviation. The ADC1 reading is 18 & ADC2 is 414.

Can someone please explain what's going on and should I now put in a density offset compensation? If so what value?

I normally keep my tank at 26 c keeping a mixture of SPS & LPS. I am now wondering once I get a true reading what Conductivity value I should aim for. previously I held it at 53.0 Msv

MAKDENTAL
13.12.2011, 17:05
Anybody please give advice?

is it considered normal to have reading 0.2mS out if so then I'll accept -but what does density offset mean and how much should I offset if at all?

Blahenazo
13.12.2011, 19:06
Is it a new probe ?

If that is the case I would just let it run a while and recalibrate it. (your ADC values are far apart <= which is always a good indicator for calibration => means alot of resolution )

that being said , if you look online
a 0.2 ms is very minimal , so it would have minimal impact ( it could even related to temp difference or something )

I would not loose sleep over it if you look in the table below.

DENSITY CONVERSION TABLE
(Reference Temperature = 25°C)
Conductivity Density Salinity Specific
(mS/cm) (g/l) (ppt/PSU) Gravity

46.5 ms/cm 1019.7 g/l 30.2 ppt/psu 1.0223
47 ms/cm 1020 g/l 30.5 ppt/psu 1.0225
47.5 ms/cm 1020.3 g/l 30.9 ppt/psu 1.0228
48 ms/cm 1020.5 g/l 31.3 ppt/psu 1.0231
48.5 ms/cm 1020.8 g/l 31.6 ppt/psu 1.0234
49 ms/cm 1021.1 g/l 32.0 ppt/psu 1.0236
49.5 ms/cm 1021.4 g/l 32.4 ppt/psu 1.0239
50 ms/cm 1021.6 g/l 32.7 ppt/psu 1.0242
50.5 ms/cm 1021.9 g/l 33.1 ppt/psu 1.0245
51 ms/cm 1022.2 g/l 33.5 ppt/psu 1.0248
51.5 ms/cm 1022.5 g/l 33.8 ppt/psu 1.0250
52 ms/cm 1022.8 g/l 34.2 ppt/psu 1.0253