Hand-held electronic thermometer - uses diode as temperature sensor and has digital read=out and touch contact power switch

摘要

A constant current is supplied to a diode junction (21) which is mounted on the inside of the silver cap at one end of the thermometer. The voltage across the diode, which is directly proportional to the temp. is amplified (20) and fed to a peak detector and memory (19). The analogue output from the memory is fed via control logic (18) to an analogue to digital convertor (23). The B.C.-coded value is then latched (24) and fed to a liq. crystal display (26) via a driver circuit (25). Touching two contacts (14) on the body of the thermometer, switches on the power supplies (15 and 16) for a preset time. The operation of the logic and display circuits is controlled by a clock (17) and frequency divider (27). The response time of the thermometer is about one second. A series of light-emitting diodes may be used in place of the liq. crystal display.