The Use of Auto-correlation Coe cients for Variable Ordering for ROB-DDs

A constant temperature heater includes a thermistor having a positive temperature coefficient and a varistor stacked upon one another in an electrically insulating casing in such a manner that the thermistor and varistor are electrically connected in series with each other and the thermistor is in heat exchange relationship with a radiator plate on the casing. A spring in the casing presses the varistor and thermistor into firm engagement with each other and biases the thermistor into good heat conductive relation with the radiator plate. The varistor serves to reduce the transient currents in the thermistor and reduces the heat dissipation power of the thermistor, thereby providing a longer service life.