crystal-based remote thermometer

Posted on Jul 2, 2012

An economical and commercially available quartz temperature sensor, Y1 and IC1, an LTC-485 RS485 transceiver in transmitter mode, form a Pierce crystal oscillator. The sensor, an Epson HTS-206, presents a nominal frequency of 40 kHz at 25°C and a temperature coefficient of 29.6/ppm/°C (Reference 3). The transceiver`s differential-line-driver outputs deliver a frequency-coded temperature signal over a twisted-pair cable at distances as far as 1000 ft.

A second LTC-485, IC2, in receiving mode, accepts the differential data and presents a single-ended output to IC3, a PIC-16F73 processor that converts the frequency-coded temperature data and presents the temperature in Celsius format on LCD1. Click here

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