Abstract
The temperature field in circular and square plate test specimens is calculated and thereby the error from the heat exchange at the outer edge of the guard ring derived for single and double plate devices contact. The error is shown to be proportional to the reduced temperature difference (difference between the mean specimen and the ambient temperatures divided by the difference between the hot and cold plate tem peratures) and the margin of error, therefore, can be optimally reduced by an appro priate adjustment in the ambient temperature. Experiments on an extruded foam confirm the results of the analytical calculations. Diagrams and tables which are de veloped on the basis of the above derived relationships make possible estimation of margin of error for different measuring arrangements for plate devices of usual sizes.
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