Temperature sensor with remote probe

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  • Paul_B
    Automated Home Legend
    • Jul 2006
    • 608

    Temperature sensor with remote probe

    I might be confused but did a Idratek module exist that allowed for a wired probe? I had a quick look on the site but couldn't find one. The reason I'm looking for this is not strictly HA but I like to monitor the temperature of my compost bin to keep it hot composting (>45 degrees). I was using a Oregon weather station with a wireless temperature sensor that had a wired probe but this broke and company have discontinued the sensor.

    MT

    Paul
  • Karam
    Automated Home Legend
    • Mar 2005
    • 863

    #2
    If you're just looking for modest resolution/accuracy (which sounds like it) then you can use an off the shelf thermistor probe wired into a QAI module. Typically these will be NTC thermistors with resistance of around 10k @25C (the latter isn't critical so long as somewhere in the 5-50K range but will determine choice of the voltage divider balancing resistor at the QAI). Maybe a good choice for robustness would be the kind of probe used for UFH systems e.g. order code MC01882 from CPC, but don't hang me on this as I haven't got direct experience with these. You should be able to get a resolution of ~0.5C and accuracy will in part be dependent on the probe + QAI conversion accuracy, maybe 2% is possible.

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    • Paul_B
      Automated Home Legend
      • Jul 2006
      • 608

      #3
      Thanks Karam, I had forgotten about this as an option

      Paul

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      • chris_j_hunter
        Automated Home Legend
        • Dec 2007
        • 1713

        #4
        we've used NTC sensors (from Rapid) wired to QAIs in several locations, without problem, apart from the resolution being a bit coarse (readings change in about 0.4degC steps, we find), which can make correction a bit tricky …

        ie: our sensors are mostly strapped-on, rather than immersed, so some correction is required … the Compensation facility (bottom-left of Behaviour window) works well, with some iteration of the Gain, which can take several goes, because of the coarse resolution …

        NB: we contrived our own logic for correction, starting with some physics / algebra, then found, with some rearrangement, the Compensation facility could do the job …

        ie: Sensor Reading = Real Temperature - factor x ( Real Temperature - Local Ambient) where the factor = 0 for no losses, 1 for all lost => S = R - f ( R - L ) => R = S + ( f / 1-f ) x ( S - L ) => R = ( S - f L ) / ( 1 - f) …
        Last edited by chris_j_hunter; 7 May 2014, 05:08 PM.
        Our self-build - going further with HA...

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