An absence of voltage indicator has an isolation circuit, an FM modulator attached to the isolation circuit, a reference oscillator, and a mixer attached to the reference oscillator and the FM modulator, wherein the output of the mixer is the difference of the two signals. In one embodiment, the FM modulator includes a variable capacitor which varies in response to a voltage in parallel to a fixed capacitor and an inductor in parallel to the capacitors.

A detector 1 detects the presence of a charged object due to a static or DC voltage source 4. The detector 1 includes a sensor 30 positioned in an electric field 3 emanating from the DC voltage source 4. A sensor signal 20 is processed by a processor 21, and, when the DC voltage source 4 is detected, the processor 21 produces an alert signal to warn a user of a potentially hazardous situation.

A detector 1 detects the presence of a charged object due to a static or DC voltage source 4. The detector 1 includes a sensor 30 positioned in an electric field 3 emanating from the DC voltage source 4. A sensor signal 20 is processed by a processor 21, and, when the DC voltage source 4 is detected, the processor 21 produces an alert signal to warn a user of a potentially hazardous situation.

A shock detector for determining the existence of a voltage gradient in a body of water, which may be remote from a structure and providing an alarm when the voltage gradient comprises a hazardous electrical condition that could injure or kill are person coming into contact with the body of water.

A shock detector for determining the existence of a voltage gradient in a body of water, which may be remote from a structure and providing an alarm when the voltage gradient comprises a hazardous electrical condition that could injure or kill are person coming into contact with the body of water.

A selector circuit selects either a class upper-limit voltage or a class lower-limit voltage as a reference voltage of a comparator. A control logic controls the selector circuit, and generates a count-up signal or a count-down signal in accordance with the output of the comparator. An up/down counter counts up upon reception of the count-up signal from the control logic, and counts down upon reception of the count-down signal. A digital-analog converter outputs the class upper-limit voltage and the class lower-limit voltage in accordance with a digital value that is outputted by the up/down counter. A timer circuit is configured to be reset by the count-up signal from the control logic to the up/down counter.

A selector circuit selects either a class upper-limit voltage or a class lower-limit voltage as a reference voltage of a comparator. A control logic controls the selector circuit, and generates a count-up signal or a count-down signal in accordance with the output of the comparator. An up/down counter counts up upon reception of the count-up signal from the control logic, and counts down upon reception of the count-down signal. A digital-analog converter outputs the class upper-limit voltage and the class lower-limit voltage in accordance with a digital value that is outputted by the up/down counter. A timer circuit is configured to be reset by the count-up signal from the control logic to the up/down counter.

A device includes a first transistor coupled to an input voltage source and to an output voltage node and an amplifier comprising a first input, a second input, and an output. The device also includes a second transistor coupled to the input voltage source and the first input of the amplifier and a third transistor coupled to the second transistor and a ground node. The third transistor includes a control terminal coupled to the output of the amplifier. The device also includes a first voltage-controlled voltage source coupled to a control terminal of the first transistor and a control terminal of the second transistor and a second voltage-controlled voltage source coupled to the first transistor and the second input of the amplifier.

A device includes a first transistor coupled to an input voltage source and to an output voltage node and an amplifier comprising a first input, a second input, and an output. The device also includes a second transistor coupled to the input voltage source and the first input of the amplifier and a third transistor coupled to the second transistor and a ground node. The third transistor includes a control terminal coupled to the output of the amplifier. The device also includes a first voltage-controlled voltage source coupled to a control terminal of the first transistor and a control terminal of the second transistor and a second voltage-controlled voltage source coupled to the first transistor and the second input of the amplifier.

A flexible sheet-type leak sensor device according to the present invention comprises: a flexible base sheet made of a non-conductive fluorine-based synthetic resin comprising ethylene tetrafluoroethylene (ETFE); conductive lines formed on a surface of the base sheet so as to have a predetermined pattern and so as not to meet or cross each other, the conductive lines being formed by depositing on the base sheet surface a carbon black-containing, conductive fluorine-based synthetic resin comprising ethylene tetrafluoroethylene (ETFE); and a conductive material composed of pure carbon black, formed at the bottom of the conductive lines.