thermocouple aray, thermal conductivity of snow

[clouddancer]

I am trying to build a temperature probe to measure snow temperatures. I already have the wire picked out, but I am looking for a material to use as the holder. It will be mostly in the snow, but 5-10cm will be out of the snow and I don't want them to heat up with solar radiation. Can anybody tell me a material that will work best the thermal conductivity of snow is 0.6000 W/m*C

 

[tiki]

Hi clouddancer,
If you want to know the surface temperature of the snow, a pyrometer would do the best, fast and reliable. You need to know the radiation coefficient of snow/ice.
Wood, especially light wood like Balsa, has <0.2W/(m*K), glass has 0.6-0.9W/(m*K). Maybe, carbon fibre has a low thermal conductivity, in addition to it's high stability, but pure graphite has 140W/(m*K). An alloy, in Germany called &quot;Neusilber&quot; (German silver, Nickel silver, Pakfong), has 29W/(m*K). It is relatively hard, you can buy very thin pipes as laboratory equipment.
Another solution is to put the sensor nearly horizontal into the snow, to guarantee a long thermal way for the sunlight induced heat.
tiki

 

[nbucska]

Instead of thermocouple use thermistor -- its higher resistance can tolerate thinner/longer wire. <nbucska@pcperipherals.com>

 

[tiki]

Hi nbucska,
if you measure the thermocouple induced voltage with a relatively high impedance, the impedance of the wires will be neglible, and it will not self-heat. But the small voltages may require a preamplifier with very good dc-performance (chopper).
tiki