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    Calibration of humidity sensor not working

    Am trying out mcsTemperature with a Temp08 I just got (with 3 remote temp/humidity sensors). Am impressed so far, but I ran into a small but, I think, importance snag.

    Am not able to calibrate the humidity sensors. The output readings (virtual device and database) are not incremented by the +2, +8 and +7 I've put in the Cal/Avg column. What am I missing?

    The temperature sensors are calibrating okay.

    By the way, how good are these offsets over a large range of temperatures (i.e. with the sensor I plan to use outdoors)?

    Also - and I realize this is more of a hardware issue - the humidity sensors (all 3 at different times) occasionally read 0. The temp sensors haven't done that yet. Is this normal? Anything I can tweak to eliminate 0 readings?

    #2
    My apologies, I threw up a bunch of questions when I posted last week, and only one was about mcsTemperature. I got carried away. Please ignore the other questions.

    Does anyone know how to (if I can) calibrate a humidity sensor. I put various numbers in the Cal/Avg column of the Analog(1) tab in Setup GUI. The calibration works for Temperature sensors, but not Humidity sensors. I tried changing field type from "Humidity" to "Temperature" and then to "Humidity Rate" for fun but it didn't fix the problem for those particular database fields.

    If this has already been asked/answered, please let me know. I may not have used the right search terms, or may have missed it in the result sets.

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      #3
      For Temp sensors the cal/bias is a bias added to the reading. For other sensors, I believe, it is a smooting factor with a value between 0 and 1 with a value of 0 meaning that no smooting will occur and a value of 1 meaning that the old value will never change.

      The humidity sensor has special provisions to limit it to 100% and to take unreasonably low reading and convert them to 100%. There was much discussion on the calibration of humidity sensors in the past and this approach to handling it was the consensus due to the physics of how the device works.

      There is also a checkbox on how to handle bad readings. It is either dont change from the prior reading or to set it to zero. Zero values will show up as dropouts in the line charts.

      For sensors such as wind speed the smooting function works well. Humidity sensors, depending upon the application, will likely change slowly so applying a smoothing calibration to these should also give good results. I'm happy with the clamping of the raw sensor data in my case.

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        #4
        humidity sensor calibration revisited

        Have been using my three Midon MD3020E humidity sensors for some time now with MCS Temperature and have not encountered any wild humidity swings (other than bad readings, which are dealt with elsewhere).

        Can the calibration of humidity sensors be dealt with the same as temperature sensors, i.e. an offset rather than a "smoothing" factor?

        The sensors are consistently off by a few degrees and I wonder if the smoothing wasn't originally implemented to deal with swings caused by bad readings before the other mechanisms were implemented for those.

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          #5
          The DS2438 for the Humidity sensor should return a Temperature and a Humidity. The Temperature reading can be biased like any other temperature. The Humidity reading will have averaging if so entered.

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            #6
            If you're politely telling me "no", fine, but if you just mis-read my question, I'm asking if you could make mcsTemp behave the same way for a humidity reading calibration as it does for a temperature reading calibration, since, in my experience and apparently yours, it does not change wildly (like a wind speed reading).

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              #7
              Yes I misread. I thought you were asking about the Temp sensor that is part of the DS2438. I could be able to do this. The setup options are really close to the limit of number of controls allowed on a form and I'm not going to split the form on this version.

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                #8
                Running 4.32.3

                Have been trying latest version with humidity calibration bias vs average check box and it doesn't work for me. I have 3 sensors with values of +2, +2, +4 and the box checked so it is a bias (i.e. offset) not an average.

                One of the three sensors was offset by -1 for while (today it's not offset) and the other 2 are not offset at all.

                See also this thread for some humidity sensor specific reading issues. http://forums.homeseer.com/showthread.php?t=101151
                Last edited by johnnyt; January 17, 2005, 09:20 PM. Reason: straighten up terminology: "average" and "bias"

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