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Best non-contact temperature sensor for metal?

Discussion in 'General Electronics Discussion' started by Doug3004, Jul 14, 2018.

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  1. Doug3004

    Doug3004

    119
    23
    Sep 5, 2014
    I have an Arduino thing I have built, that is an oven for making rubber strips.

    What this is, is a heating element with a strip of aluminum suspended ~3 inches above it on wires. I need to monitor the temperature of the strip to keep it 130 to maybe 150F, and within about 5 degrees over or under. The wet rubber is extruded on top of the strip.

    The previous enclosed version of this oven used a TMP36 sensor that was accurate enough, but that was in an enclosed air space, which this version doesn't have. The TMP36 is an analog sensor in an ordinary plastic TO-92 case, so it doesn't really have any directional discrimination. I was going to try using it by placing it near the underside of the strip, but am wondering if an IR/non-contact sensor might do better. I could spend maybe $50 tops here, and it must be something I can connect to the Arduino, since that is the timer & heater control being used.

    There is a lot of IR-type sensors around, but I have not used them in a project before. I have seen in the past that cheaper IR thermometers don't work correctly on polished metal due to the metal's surface not radiating heat normally. Really expensive lab/industrial IR thermometers have the ability to use an emissivity setting to try to account for this problem, but mathematically (or circuit-wise) I don't know how they do that...
    http://www.pyrometer.com/Products/Non-Contact-IR

    Are there any sensors that avoid that problem entirely? Or is there any info online about how it can be estimated from a reading from a normal non-contact sensor?
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,906
    2,098
    Nov 17, 2011
    Most likely not. A direct contact sensor will give the most accurate reading.

    An IR sensor needs to be calibrated and as you noticed works best for surfaces that are "black" in the IR spectrum, not on polished metal.
     
  3. WHONOES

    WHONOES

    859
    206
    May 20, 2017
    Try a platinum thermometer element. They generally come in a ceramic package. They are very predictable but will need a small amount of electronics to realise the control that you require. The 5 degrees of hysteresis you want would be easily achievable.
     
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