Measuring heat leak with a heatmeter

The heatmeter or more precisely the heatflowmeter is a device based on thermal conductivity measuring techniques. It consists of a thermal conducting body between two thermometers, with provisions for thermal connections and calibration. The paper describes the design, construction details, calibration and performance of one such heatmeter for use with heat reservoirs at either 4.2 K or 78 K. Near 4.2 K it has a sensitivity of 10 micro W and requires less than a minute to reach steady state. Near 78 K its sensitivity is 10 MW and requires 25 minutes to reach steady state.