The increasing application of sensor networks in many different fields causes a growing demand of low-cost passive
sensors for monitoring physical variables as temperature, pressure or ambient humidity. These sensors need a
conditioning circuit that allows an easy interface to a microcontroller, taking advantage of the full range of the sensor
and reducing the microcontroller requirements. This paper presents a conditioning electronics designed to transform the
output of low-cost resistive sensors to a frequency variable signal. The circuit is designed to use the full frequency range
available, providing a good resolution. These quasi-digital signals are compatible to the logic levels of a standard low-power
microcontroller, allowing its connection through a digital I/O port.