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Linear temperature-to-frequency

2017-03-18 20:24  
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This circuit provides a linear increase of frequency of 10 Hz/?°C over 0-100 ?°C and can thus be used with logic systems, including microprocessors. Temperature probes Ql Vbe changes 2 mV/?°C. This transistor is incorporated in a constant current source circuit. Thus, a current proportional to temperature will be available to charge Cl. The circuit is powered via the temperature stable reference voltage supplied by the 741
Linear temperature-to-frequency

Comparator ICl is used as a Schmitt trigger whose output is used to discharge Cl via Dl. To calibrate the circuit Ql is immersed in boiling distilled water and PR1 adjusted to give 1 kHz output. The prototype was found to be accurate to within 0 ?°C.

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