Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1983-06-06
1986-01-28
Rowland, James L.
Communications: electrical
Condition responsive indicating system
Specific condition
340585, 340586, 340599, 340663, 340687, G08B 2100
Patent
active
045674744
ABSTRACT:
A device simply and effectively senses undesirably high temperatures in a refrigerated volume with an accuracy of about 3 percent, and activates an indicator in response to the sensing. A temperature probe is disposed in a freezer, refrigerator, or cooler volume, the probe including a negative temperature coefficient thermistor forming part of a voltage measurement bridge. The resistors of the voltage measurement bridge are all accurate to one percent, and are connected up to a voltage comparator of an integrated circuit. A 9 volt battery powers the device. The device also includes a low battery voltage sensor for activating the indicator when the battery voltage drops below about 8.2 volts, and a sensor for detecting when the probe is damaged or disconnected. The probe detection circuit includes a Darlington transistor, and resistor, the Darlington transistor being connected through a diode to the indicator. The indicator may include a piezo electric horn driven by a horn oscillator circuit.
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"Temperature Monitor", Elektor, vol. 1, No. 5, p. 742, Jul.-Aug. 1975.
Prior Public Use Freezer High-Temperature Protection Device, Oct. 1981.
Mullen Jr. Thomas J.
Rowland James L.
Temco Products Corporation
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