Evaluation of insulated miniature thermistors for skin temperature measurement in the rat

A miniature thermistor modified by covering its outer surface with insulating foam was evaluated as a temperature sensor at three skin sites in the adult male laboratory rat. A high precision thermistor was modified by covering the outer epoxy surface with about 1/4 inch of a commercially available insulating foam. Such foam thickness provided sufficient insulation to reduce the influence of ambient temperature on the thermistor reading yet contributed minimal additional probe weight. Results indicate that compared to the insulated thermistor, the uninsulated probe underestimated skin temperature measured at the midscapular region of the back, ventral surface of the foot, and dorsal base of the tail at cool ambient temperature (25c) and overestimated temperature at the back and tail skin sites at high ambient temperature (42c). The differences in temperature measured by the insulated and uninsulated thermistors were greastest at the back skin site, which was the only fur-covered and the least vascularized area of the rat that we studied. Using an insulated miniature thermistor to reduce the influence of environmental temperature on thermistor readings when measuring skin temperature in a furred laboratory animal is recommended.