Abstract: A probe having a temperature sensor mounted in its tip for measuring the temperature of a body into which the probe is inserted, has a heating coil positioned on the shank of the probe near the tip, and a second temperature sensor in the tip area positioned generally between the coil and the first sensor. A control circuit is operative to energize the heater coil in response to differences in the temperature sensed by the two sensors, so that the shank of the probe is heated to track the temperature rise of the tip of the probe upon insertion into a body whose temperature is to be measured. This heat servo thermally isolates the tip from the remainder of the probe, and eliminates long thermal time constants which would otherwise be associated with the flow of heat from the tip area down the probe shank.

Abstract: A highly accurate low-cost electronic thermometer with digital readout, intended primarily for clinical use. Temperature sensing is accomplished by a thermistor in a probe assembly which includes a unique disposable probe cover which provides excellent thermal contact with the thermistor to a measuring circuit which includes a bridge and a rebalancing servo. Digital readout is accomplished by a coding disc driven by the servo and pickoff brushes. The coding pattern on the disc provides analog to digital conversion, compensation for the inherent nonlinearities of the thermistor, and a nonvolatile memory. Means are provided for operating the thermometer in an estimation mode to give readings more quickly than would be otherwise permitted by the thermal response of the probe. In estimation mode, measurement is terminated at a predetermined point in the measurement cycle, and a special calibration of the measurement circuit is used to give an estimate of what the final temperature would be.