Temp. regulating circuitry for electrical heating element - uses current measuring resistor and reference voltage forming divider consisting of ohmic resistors in series with element

摘要

The circuitry regulates the temp. of a heating conductor (2) connectable at a DC or an AC source via a switching element (3). A current measuring resistance (4) lies in series to the heating conductor as does a reference voltage divider consisting of ohmic resistances (5, 6, 14), the end side connections of which are connected to the corresp. connections of the voltage divider formed by the heating conductor and the current measuring resistance. The voltage drop at the current measuring resistance is compared with the desired voltage drop at the tapping of the reference voltage divider by a comparator (7). The switching element is opened or closed according to the logic position of the comparator. A pulse transmitter (16, 20) is periodically closed for carrying out a voltage comparison through the comparator (7). For the operation at an AC source, a storage element (13) is provided, which stores the output signal (8) of the comparator in-between. USE/ADVANTAGE - Facilitates regulating by exact measuring of resistance alteration of heating conductor during operatoin. Fluctuations of supply due to interference are suppressed. Heating element of air heating appts., lubrication warmer, car seats heater, hair dryer.