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Thema: conductivity question- strange thing?

  1. #1
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    Frage conductivity question- strange thing?

    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
    Geändert von MAKDENTAL (13.12.2011 um 16:06 Uhr) Grund: clarity

  2. #2
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    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?

  3. #3
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    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.

    (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



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