Welch Allyn SureTemp PlusModule - User Manual - Manual (Page 9)

SureTemp Plus Module OEM Implementation Product Overview
Welch Allyn OEM Technologies Confidential 9
Measuring Principle
The Welch Allyn proprietary probe utilizes a negative temperature coefficient (NTC) thermistor
and control circuitry in combination with the SureTemp Plus module’s predictive algorithm to
calculate patient temperatures.
NTC thermistors have a large temperature coefficient of resistance and change in resistance as
temperature changes. This predictable change in resistance is the basis for predictive
thermometry.
The oral/axillary probe is pre-warmed to 34
°
C (93
°
F) upon extraction from the probe well. The
probe-warmer circuitry is used to heat the probe tip before taking a temperature reading to speed
the convergence of the prediction algorithm. A fail-safe hardware shut-off circuit is included to
ensure that the heater shuts down in the event of a software failure.
When the probe is placed in the mouth, the heat supplied by the mouth reduces pulse widths to
zero.
The shape of the rising temperature curve is monitored and the best fit to a curve is found. When
the curve fit is stable, the final predicted temperature is provided.
The module can determine the type of probe connected.