Need help with Thermistor use and Data-logger for snow column.

Discussion in 'The Projects Forum' started by vega1ice, Feb 6, 2009.

  1. vega1ice

    Thread Starter New Member

    Feb 6, 2009
    Okay the title was weak I know, but I'm green here so be patient. I'm working on a project to determine if I can take measurements of snow in graduated 10 CM increments utilizing thermistors, specifically how I do it.

    I wanting to get is temperature spreads throughout the season in a snow pack in Alaska for avalanche control. Usually we have snow that remains right around 0 degrees Celsius, but other times we don't mainly near the surface of the snow-pack on cold nights. Now I take temps manually with a thermometer, and it's a pain.

    I'm envisioning a long sturdy PVC pipe, with holes all the way up say a 400 CM post, with a macrame of wires feeding all these thermistors into my Multiplexer, which only has 32 channels so it will probably end up being less than 10 CM.

    Any help at all would be greatly appreciated.
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    You might want to use LM35's. The device has a linear output calibrated in deg. C. It has 3 legs, one for ground, one for any voltage from +4 to +20 VDC, and an output, which is 10 mv/deg. C. Pretty handy.

    The full-range critter goes to -55 C, good for Alaska. Lots easier to use than thermistors - no calibration curve to worry about. Google "lm35" and get the data sheet.
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007

    Will your datalogger accept thermocouple inputs? For this purpose they might be more rugged than thermistors. We did this to monitor the temperature gradient at several points, for 80 meters down a Bergschrund as it filled and opened over the winter.

    Just another option.

  4. Søren

    Senior Member

    Sep 2, 2006

    I assume you mean cm (centimeter) rather than CM?

    I don't think you need to make holes in the pipe, as long as you can place the sensors up against the wall and as long as it is going to stay for some time.
    The temp. will change slowly and the temp of the pipe will follow.
    It would make the pipe stronger and smoother to ram into the snow (plus easier to secure the wiring and components in the tube from moisture giving false readings).

    You could expand your multiplexer with eg. 8 inputs a pop (with cheap CMOS multiplexers) connected to each of your current multiplexers inputs if needed.

    What kind of temperature range and what kind of precision do you need?

    As others have mentioned, there are lots of other thermo-sensor types, but thermistors might be the simplest solution and I assume that is a major factor, as almost any other type will need more elaborate circuitry.