US PATENT SUBCLASS 219 / 497
.~.~.~ Comprising voltage and/or current measuring and comparing or combining means

Current as of: June, 1999
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219 /   HD   ELECTRIC HEATING

200  DF  HEATING DEVICES {14}
482  DF  .~ With power supply and voltage or current regulation or current control means {4}
490  DF  .~.~ Automatic regulating or control means {11}
497.~.~.~ Comprising voltage and/or current measuring and comparing or combining means {2}
498  DF  .~.~.~.~> Including follow-up servo means
499  DF  .~.~.~.~> Including bridge means

DEFINITION

Classification: 219/497

(under subclass 490) Subject matter including means for deriving at least one first voltage, the magnitude of which is dependent upon some variable of a heated space or material, means for producing a second reference voltage representative of a desirable condition, means for comparing or combining the two derived voltages and further means whereby the condition of a heating device is adjusted by application of the voltage resulting from the combination or comparison of the two or more derived voltages.

SEE OR SEARCH THIS CLASS, SUBCLASS:

494+, for heaters wherein the voltage or current combined or compared with the standard is derived from the temperature of the heater.

496, for heater control systems wherein the variable voltage or current compared or combined with the standard is derived from changes in pressure of the heated medium or structure.

SEE OR SEARCH CLASS

323, Electricity: Power Supply or Regulation Systems, 234, 298, which regulators or systems may be controlled by comparing a change in the electrical condition controlled with some standard or pre-set voltage or current.