Temp. regulator for convection heater - uses thermistor close to heat sink of power control thyristor to compensate local heating effects on measuring thyristors

摘要

The regulator for electric convection heaters incorporates a circuit which compensates the effect on the temp. transducer of heat transmitted directly from the controller and radiator. The electronic circuit is mounted on a printed circuit board which forms the base (A) of the regulator enclosure, and the main power controller thyristor (TR1) is mounted on the aluminium lid (B) of the enclosure. An external thermistor measures the room air temp. while a second thermistor (T2), mounted near the main thyristor (TR1), provides a measure of the power being supplied to the convection heater. The temp. characteristics of the second thermistor (T2) is opposite to that of the air temp. transducer, thus removing from the air temp. measurement local heating effects caused by the heat source.