초록 ▼

A thermostat for heating or cooling, operative to maintain an indoor air temperature to a limited setpoint range, is provided with a comparison circuit to prevent tampering intended to exceed a setpoint limit. A first temperature sensor responds to ambient air temperature and can include a first the

A thermostat for heating or cooling, operative to maintain an indoor air temperature to a limited setpoint range, is provided with a comparison circuit to prevent tampering intended to exceed a setpoint limit. A first temperature sensor responds to ambient air temperature and can include a first thermistor. A second thermistor is partly thermally isolated from the air, and senses a reference temperature that lags temperature changes in the ambient air. The two thermistors form a voltage divider coupled to one input of a differential amplifier comparator, the other input of which is coupled to a fixed voltage reference. When the ambient and reference temperatures exceed a predetermined temperature difference, the differential amplifier operates a relay that breaks a circuit including the contacts. This occurs when locally cooling the ambient air to generate a spurious call for heat (or vice versa). Two differential comparators can be included to sense positive or negative differences between the ambient and reference temperatures, and can be set to respond to different temperature differences using jumpers. A third temperature sensor can be similarly coupled to a low temperature responsive differential comparator that inhibits operation of the tamper-resistant circuit at an absolute low safety threshold temperature (i.e., to permit a call for heat), and/or coupled to a high temperature responsive comparator, to block a call for heat redundantly, above a high temperature threshold.

대표청구항 ▼

An apparatus for a thermostat operable to generate a signal calling for at least one of heating and cooling, for maintaining a temperature of indoor air to be heated or cooled to maintain a setpoint temperature defined by the thermostat, comprising: a first temperature sensor responsive to an ambien

An apparatus for a thermostat operable to generate a signal calling for at least one of heating and cooling, for maintaining a temperature of indoor air to be heated or cooled to maintain a setpoint temperature defined by the thermostat, comprising: a first temperature sensor responsive to an ambient temperature of the air; switching means responsive to the first temperature sensor, the switching means normally generating the signal calling for said one of said heating and cooling when the ambient temperature and the setpoint temperature differ such that the ambient temperature is to be changed to approach the setpoint temperature; a second temperature sensor partly thermally insulated from the air, whereby changes in the reference temperature lag corresponding changes in the ambient temperature, the second temperature sensor thereby sensing a reference temperature; means for comparing the ambient temperature and the reference temperature, and disabling the switching means when the reference temperature differs from the ambient temperature by a predetermined amount, whereby the thermostat is insensitive to local cooling or heating of the ambient air for generating a call for heating or cooling, respectively.