Electric automatic temperature control
US5397874A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 26, 1991 |
| Grant date | Mar 14, 1995 |
| Priority date | — |
| Expiry date | Aug 26, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG05D23/24
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A temperature control circuit is disclosed utilizing automatically either the electric heating (or cooling) element or a separate sensor to measure the instantaneous temperature of the thermal load device. Either a pulsating dc or an ac electric power source may be used with the temperature sensing occurring at near-zero points of the source voltage waveform. The sensor forms one element of a Wheatstone bridge which when unbalanced by a value lower than a chosen reference value, causes a monostable oscillator to flip for at least several cycles of the source power. This turns on a power SCR to feed electric current to the thermal load to increase its temperature (and resistance) until the bridge is again balanced to reverse the state of the monostable oscillator and turn off the SCR. A simple, reliable two step, user friendly calibration circuit is provided for the temperature selecting component. For multiple channel applications the circuit need be reiterated only in part whereby major portions thereof remain common to the various channels and need not be duplicated, thereby minimizing manufacturing cost, component space, heat generation, and power consumption.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.