Both temperature and moisture ?

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This topic contains 3 replies, has 2 voices, and was last updated by  Brian Young 9 months, 4 weeks ago.

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  • #1318

    Mathieu Le Breton
    Community Member
    • ★★★★

    Hi,

    We are interested in measuring both temperature and moisture, at a large range, for outdoor environmental monitoring. On the datasheet, the Magnus S3 would do it. However, there is no tag advertised as doing both, it’s either moisture (based on S2), or temperature (based on S3). I guess the moisture sensing capability mainly comes from the tag antenna design.

    Would the tag RFM3240 work also for moisture sensing ?
    Otherwise, would you have a tag on the shelf that can do both ?

    Best regards,

    Mathieu

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    #1319

    Brian Young
    RFMicron Team Member
    • ★★★★

    The marketing messaging can make this a little difficult.  With the exception of the RFM3240, all of our sensors have the adaptive frontend enabling moisture sensing.  An S3 is an S2 with added temperature sensing plus improvements in a number of areas.  The RFM3240 is the exception because the adaptive frontend is not present on the chip, so it cannot measure moisture.

    The S3-based sensors that can measure both moisture and temperature are the RFM3200, RFM3250, and RFM3254.  The RFM3260  is not practical as a moisture sensor because the antenna is protected within the plastic housing.

    The amount of sensor code movement varies from sensor to sensor depending on the amount of water present and the location of the water.  The water detunes the antenna and the adaptive frontend adjusts to compensate, leading to the detection of moisture.  Since every antenna behaves a little differently, the moisture sensitivity varies with the antenna design.  The sensitivity of the sensor code movement also varies with the location of the water on the antenna since some areas are far more sensitive than others.

     

     

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    #1320

    Mathieu Le Breton
    Community Member
    • ★★★★

    Hi Brian, thank you very much for the information !
    So the RFM 3200 would work great (and I can forget the RFM3240).

    Still, the antenna of the RFM 21000 has a ‘Z’ shape near the IC, which may increase its sensitivity to moisture, but which is not on the RFM3200. On the other side, the better resolution of the S3 may compensate for any potential sensitivity decrease.
    Is that correct ?

    Anyway, I should probably test both, as my major immediate concern is moisture.

    Thank you again for the information.

    Mathieu

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    #1321

    Brian Young
    RFMicron Team Member
    • ★★★★

    The RFM2100 and RFM3200 are indeed very similar.  The RFM2100 has an inter-digitated capacitor added to increase its sensitivity to moisture.  One way to think about it is that the RFM2100 is a high-sensitivity moisture sensor with less dynamic range and the RFM3200 is a low-sensitivity moisture sensor with more dynamic range.

    Given the time your post came in, I am assuming that you are interested in operating in Europe in the narrow ETSI band.  S3 has a big advantage over S2 in the ETSI band because the resolution at a given frequency is much better than S2.  In the wide North America FCC band, the sensor can be read at many channels, so the S2 resolution can approach that of the S3 through post-processing.

    Because of the very large range of applications involving moisture, testing is the best way to work out the best sensor to use.  So your plan looks good.

     

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