Performance Test of Steel Tube Enclosed Thermistors in Air Temperature Measurements

The performances of two steel tube enclosed precision thermistors are tested in a well controlled air environment to determine if the thermistors have enough accuracy for ±0.01°C levels of air temperature gradient measurement. Three Fluke´s 5641 and three 5610 thermistors were tested for 24 hours in Fluke´s 7008 calibration bath in the first step. In the second step, two of the 5641s were airproofed in a temperature well controlled tube, the performances of these two thermistors in steady state and transient state air temperature environments were tested for 8 hours separately. The results illustrate that, when steel tube enclosed precision thermistors are used in air temperature measurement, there are unstable departures from each other with a maximum 8.8 m°C in constant air medium and 27 m°C in temperature changing air medium. The transient-time errors are too large to show the true amounts of temperature changes for air temperature measurement.