Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Patent
1995-07-21
1998-04-28
Nguyen, Vinh P.
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
374183, 236 78R, 236916, G01R 2708, G05D 2300, G01K 700
Patent
active
057449732
ABSTRACT:
A resistance to frequency circuit for measuring the ambient temperature on a thermostat. The temperature measuring circuit comprises a first Schmitt trigger NAND gate, a rectifier, a capacitor of which one terminal is electrically connected to ground, a first resistor, a thermistor and possibly a second resistor. The capacitor is connected with the cathode electrically connected to ground, the anode is electrically connected to the first input of a NAND gate. The output of the NAND gate is electrically connected to the anode of the rectifier. The cathode of the rectifier is electrically connected to both the thermistor and the first resistor. The second terminal of the first resistor is electrically connected to the anode of the capacitor and the first input to the NAND gate. The thermistor is electrically connected to a tri-state buffer of the microprocessor. The circuit uses the open drain output ports of a microprocessor to provide the multiplexer function of the A/D. Two precision resistors are connected to the cathode of the rectifier with their second terminals electrically connected to a second and third tri-state buffer. By selectively switching through the tri-state buffers, and measuring the resulting frequencies, errors in the system can be calculated and thereby eliminated from the measured temperature of the system.
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Richard Friedl & Peter Seyfried, A New Resistance-to-Frequency Converter for Temperature Measurements in Calorimeters, IEEE Transactions on Instrumentation and Measurements in Calorimeters, IEEE Transactions on Instrumentation and Measurement, vol. IM-24, No. 4, Dec. 1975.
Honeywell Inc.
MacKinnon Ian D.
Nguyen Vinh P.
Valone Thomas
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