Capacitance monitoring bridge circuit for an enthalpy responsive device
AssigneeHoneywell Inc.
InventorArlon D. Kompelien
Life of this patent
Estimating the term…
Abstract
An enthalpy control circuit has a humidity responsive capacitive element in one leg of a bridge circuit and a temperature responsive resistance element in another leg. The circuit is powered by a pulsating DC voltage of 1 kilohertz frequency for providing DC output, from an integrator connected to the output of the bridge circuit, indicative of enthalpy. A feedback from an integrator output to the bridge circuit is provided by chopping the DC output into appropriate AC for rebalance. Another feedback circuit around an amplifier provides a reference point compensated for offset voltages brought about by conditions such as temperature affecting circuit components.
Claims7
In a control circuit comprising
- moisture responsive capacitance means having a capacitance which varies with the amount of humidity in the surrounding air,
- bridge circuit means having an input power circuit and an output circuit for providing an output when said bridge circuit means is unbalanced,
- means connecting said moisture responsive means in one branch of said bridge circuit,
- bridge power supply means providing a pulsating DC voltage at a predetermined frequency and connected to said input power circuit,
- amplifier circuit means having a reference input circuit,
- integrator circuit means having an input circuit for receiving a pulsating signal and an output circuit providing a DC output voltage,
- means connecting said output circuit of said bridge circuit to said input circuit of said integrator circuit means through said amplifier circuit means whereby said DC voltage is indicative of humidity,
- first feedback circuit means comprising switch means synchronized with said predetermined frequency connecting the DC output voltage of said integrator circuit means to said bridge circuit means for providing a voltage to balance said bridge circuit means.
Dependencies are inferred from the claim text.