# Calibrating an electronic temperature sensor based on power consumption

I'm working with an electronic temperature logger that is being affected by heat generated internally.

How does one come up with a calibration equation to calculate a more accurate reading of ambient temperature based on what the temperature sensor reads, taking into account its own power consumption?

details:

After a few hours and in equilibrium, the sensor reports values that are actually 1 degree Celsius higher than the ambient room temperature (22C) measured by a calibrated device. The sensor is accurate to 0.1 degree C at reporting the temperature of the device itself (which due to heat generated by the electronics has gotten warmer)

The device consumes ~0.1 watts of power, weighs about 200g and has an average specific heat capacity of 1.0 j/g (weighted mix of glass, abs, fr-4, copper). Dimensions are 1"x 3"x 4".

What I've got so far is this heating calculation: 200g * 1c * 1.0j/g / 0.1w / 60s = ~33 minutes to heat up 1 degree.

I'm assuming what we need is to figure out Sensor value - Heat-generated + Heat-dissipated to arrive at actual temperature. Which will require measure the K in newton's law? then what?

I'd really appreciate you help here.

• Are you sure that the operating heat is not affecting the immediate environment to that degree? Simulation suggests that if some of the sensor packages we installed in the Double Chooz far detector were left running full time they could affect the immediate environment to that level. (Of course that is in a very static environment, and packages that combine several instruments.) Accordingly we only power up the most power-hungry parts of the boards for a few seconds every five minutes or so. Oct 18, 2012 at 18:09
• I make a point of measuring ambient temp a few cm away from the device. knowing the heat generation rate (measure and computed) and measuring the dead device cooling rate, I'd like to be able to infer what the ambient temperature was if the sensor reports a given T. Oct 18, 2012 at 18:38