The measuring instrument WM 694 realises the measurement of the thermal resistance of power semiconductors.
The measurement of the temperature increase in a pn- junction is enabled by the relatively defined temperature behaviour of the forward voltage at small current density. This temperature coefficient is typically in a range of -2mV/K and the variance is small for samples taken from the same production run.
Measuring before and after a power pulse the temperature increase is measurable.
These results are used to calculate RTH or ZTH.
The test system is controlled by a microprocessor situated within the measurement unit. All test parameters, actual test methods and results are transmitted via serial interface to the operating PC.