Almost all temperature sensor circuits use some form
of discrete component (such as a thermistor or a solid-
state sensor) to actually measure the environment’s
temperature. It is left to the microcontroller to interpret
the reading into a human-friendly form for the user’s
benefit.
It is possible, however, to design a digital thermometer
without an external sensor, by using a temperature
sensitive property of the microcontroller itself. This
Application Note shows how to use the Watchdog
Timer (WDT) of a PICmicro
®
microcontroller for tem-
perature measurement.M AN828
Measuring Temperature with the
PIC16F84A Watchdog Timer
Author: Leena Chaudhari THEORY OF OPERATION
Microchip Technology Inc.
The WDT on all PICmicro microcontrollers has a nomi-
nal time-out period of 18 ms. The WDT time-out period
varies with temperature, VDD and part-to-part process
INTRODUCTION ……
