초록 ▼

A capacitive field sensor, which may be used for the control of a water supply valve in a basin or fountain, employs a single coupling plate to detect a change in capacitance to ground. The apparatus comprises a circuit for charging a sensing electrode and a switching element acting to remove charge

A capacitive field sensor, which may be used for the control of a water supply valve in a basin or fountain, employs a single coupling plate to detect a change in capacitance to ground. The apparatus comprises a circuit for charging a sensing electrode and a switching element acting to remove charge from the sensing electrode and to transfer it to a charge detection circuit. The time interval employed for the charging and discharging steps can vary widely. Usually at least one of the charge or discharge pulses is on the order of a hundred nanoseconds, and is shorter in duration than a characteristic conduction time for a body of water disposed about the sensing plate. Thus, the sensor can detect the presence of a user near a controlled faucet without being subject to measurement artifacts arising from standing water. In a controller for a water basin, a short charge or discharge pulse duration may be used when the controlled valve is closed, and a longer duration, which allows conduction through the water, may be used when the valve is open. The long duration measurement can detect the continued presence of the user as long as the user's hand remains in the stream of water.

대표청구항 ▼

[ What is desired to be secured by Letters Patent is:] [33.] A method of measuring the change of capacitance to ground of a conducting plate and of controlling the actuation of an electrically-operated valve supplying water to a spout responsive to the measured change, the method comprising the step

[ What is desired to be secured by Letters Patent is:] [33.] A method of measuring the change of capacitance to ground of a conducting plate and of controlling the actuation of an electrically-operated valve supplying water to a spout responsive to the measured change, the method comprising the steps of:a) closing a charging switch and thereby connecting the plate to a source of dc voltage for a charging interval having a first predetermined duration;b) opening the charging switch at the conclusion of the charging interval;c) closing a discharging switch and thereby connecting the plate to a charge measurement means for a discharging interval having a second predetermined duration;d) opening the discharging switch;e) connecting the charge measurement means to a controller and reading from the charge measurement means a first quantity of charge transferred thereinto;f) comparing a first predetermined charge value stored in the controller with the first quantity of charge read from the charge measurement means; andg) controlling, by means of an electrical output from the controller, the valve to open and thereby supply water to the spout if the first quantity of charge exceeds the predetermined charge value, otherwise controlling the valve to be closed and to not supply water to the spout.