Proximity detector

Claim 2

A proximity detector, comprising a voltage sensor responsive to a change in input voltage to actuate an alarm, a pulse generator for applying pulses to said sensor, and means between the pulse generator and the voltage sensor for controlling the magnitude of said pulses, said means including a gating device having a control electrode responsive to a change in applied voltage to effect a change in current flow between two other electrodes, said two other electrodes being connected between the pulse generator and the alarm actuating device, and a probe connected to said control electrode for connection to an object to be protected, whereby a change in the capacitance of said object will cause a change in applied voltage at said control electrode to effect a change in the magnitude of said pulses.

Claim 3

A proximity detector as set out in claim 1 in which said gating device is a transistor connected in emitter-follower configuration.

Claim 4

A proximity detector as set forth in claim 1 in which said gating device is a thermionic device connected in cathode follower configuration.

Claim 5

A proximity detector as set out in claim 1 in which means is provided for charging the capacitance of said object, whereby during the off period of the pulse generator, the voltage of the capacitance of said object maintains sufficient voltage at the input of the voltage sensor to prevent an alarm from being actuated.

Claim 6

A proximity detector comprising a voltage responsive device for actuating an alarm, a pulse generator for applying pulses to said device, and current control means between said device and said pulse generator to control the magnitude of said pulses applied to said device, said current control means comprising a gating device having a control electrode responsive to a change in current to effect a change in current flow between two other electrodes, said two other electrodes being connected between the pulse generator and the voltage responsive alarm device, means supplying a current flow to said control electrode, and a probe connected to said control electrode for connection to an object to be protected, whereby an increase in capacitance of the object to which the probe is connected will cause current to flow to said object which will reduce the current flow to said control electrode and thereby reduce the magnitude of said pulses.

Claim 7

A proximity detector comprising a voltage responsive device for actuating an alarm, a pulse generator for applying pulses to said device, and current control means between said device and said pulse generator to control the magnitude of said pulses applied to said device, said current control means comprising a gating device having a control electrode responsive to a change in current to effect a change in current flow between two other electrodes, said two other electrodes being connected between the pulse generator and the voltage responsive alarm device, means supplying a current flow to said control electrode, and a probe connected to said control electrode for connection to an object to be protected, whereby an increase in capacitance of the object to which the probe is connected will cause current to flow to said object which will reduce the current flow to said control electrode and thereby reduce the magnitude of said pulses.

Claim 8

A proximity detector, comprising a voltage sensor responsive to a change in voltage to operate a circuit component, a voltage integrating device having its output connected to the input of the voltage sensor, a pulse generator for applying current pulses to said integrating device to normally maintain a predetermined voltage at said voltage sensor, and current control means between the pulse generator and the integrating circuit, said current control means comprising a transistor connected in emitter-follower configuration whereby the pulses pass from the pulse generator through the collector-emitter path of the transistor and provide pulses at the integrating circuit, and a current controlling input connecteD to the base of said transistor, said input comprising a bias current to normally allow a pre-determined current flow in the collector-emitter path, and a probe for connection to an object to be protected, whereby an increase in capacitance between the object and ground will cause less bias current to flow to the base, whereby the current in the collector emitter circuit is reduced causing a reduction in current to the integrating device, whereby less voltage appears at the voltage sensor.

Claim 9

A proximity detector, comprising a voltage sensor responsive to a change in voltage to operate a circuit component, a voltage integrating device having its output connected to the input of the voltage sensor, a pulse generator for applying current pulses to said integrating device to normally maintain a predetermined voltage at said voltage sensor, and current control means between the pulse generator and the integrating circuit, said current control means comprising a transistor connected in emitter-follower configuration whereby the pulses pass from the pulse generator through the collector-emitter path of the transistor and provide pulses at the integrating circuit, and a current controlling input connecteD to the base of said transistor, said input comprising a bias current to normally allow a pre-determined current flow in the collector-emitter path, and a probe for connection to an object to be protected, whereby an increase in capacitance between the object and ground will cause less bias current to flow to the base, whereby the current in the collector emitter circuit is reduced causing a reduction in current to the integrating device, whereby less voltage appears at the voltage sensor.

Claim 10

A proximity detector, comprising a transistor having base, emitter, and collector electrodes, means for supplying a voltage to the base from a high impedence source of a polarity such that conduction can occur in the emitter-collector path, means for supplying pulses to the emitter-collector path, means for integrating the pulsed output from the emitter-collector path into a voltage signal input to an alarm actuating device to maintain said device in the non-alarm condition, said alarm actuating device being responsive to a drop in signal voltage to actuate said alarm, and probe means connected to the base, whereby when the capacitance between the probe and ground increases, the voltage at the base decreases reducing the magnitude of the output pulses and thereby lowering the signal voltage to the alarm actuating device.

Claim 11

A proximity detector, comprising a transistor having base, emitter, and collector electrodes, means for supplying a voltage to the base from a high impedence source of a polarity such that conduction can occur in the emitter-collector path, means for supplying pulses to the emitter-collector path, means for integrating the pulsed output from the emitter-collector path into a voltage signal input to an alarm actuating device to maintain said device in the non-alarm condition, said alarm actuating device being responsive to a drop in signal voltage to actuate said alarm, and probe means connected to the base, whereby when the capacitance between the probe and ground increases, the voltage at the base decreases reducing the magnitude of the output pulses and thereby lowering the signal voltage to the alarm actuating device.