Fluke Corporation

Michael F Gallavan

Clark N Huber

Paul Andrew Ringsrud

Ronald Steuer

Jeffrey E Worones

David Lawrence Epperson

Ricardo Rodriguez

Monte R Washburn

Christian Karl Schmitzer

Peter Radda

William F Rasnake

William J Lauby

Howard T Voorheis

Patrick Scott Hunter

Systems and methods provide measurement of alternating current (AC) electrical parameters in an insulated wire without requiring a galvanic connection between the insulated wire and a test probe. Measurement systems or instruments may include a housing that includes both a non-contact voltage sensor and a non-contact current sensor. The measurement system obtains measurements from the voltage sensor and the current sensor during a measurement time interval and processes the measurements to determine AC electrical parameters of the insulated wire. The AC electrical parameters may be presented to an operator via a visual indicator device (e.g., display, lights). The AC electrical parameters may additionally or alternatively be communicated to an external device via a wired and/or wireless communications interface. The measurement system may include an alignment feedback sensor that provides feedback to a user regarding the mechanical alignment of the insulated wire relative to the voltage sensor and the current sensor.

Non-contact electrical parameter measurement systems

Systems and methods for measuring alternating current (AC) voltage of an insulated conductor (e.g., insulated wire) are provided, without requiring a galvanic connection between the conductor and a test electrode or probe. A non-galvanic contact (or 'non-contact') voltage measurement system includes a variable capacitance subsystem which operates to generate a variable capacitive voltage between an insulated conductor under test and earth ground. During measurement, the non-contact voltage measurement system varies the capacitance of the variable capacitance subsystem to change the impedance of a capacitive divider circuit between the insulated conductor under test and earth ground. By sequentially making two (or three) measurements across the variable capacitance subsystem, the AC voltage of the insulated conductor can be determined without requiring any galvanic connection to the insulated conductor. The determined AC voltage of the insulated conductor may then be presented to an operator and/or communicated to an external device.

Variable capacitance non-contact AC voltage measurement system

An arrangement that includes a transmitter unit and a receiver for locating a circuit interrupter associated with a selected branch circuit of a power distribution system. The transmitter is electrically interconnected with the selected branch circuit and produces a sequence of tracing signals in a branch circuit that is to be traced. Each tracing signal is transmitted and detected at times measured with respect to a detected known phase of the signal on the branch circuit. In one embodiment, tracing signals are transmitted on a branch circuit of a 3 phase power distribution system when the branch circuit to be tested has a positive phase and the other phases are negative.

AC voltage phase discriminator for circuit breaker locators

An arrangement that includes a transmitter unit and a receiver for locating a wire or a circuit interrupter associated with a selected branch circuit of a power distribution system. The transmitter is electrically interconnected with the selected branch circuit and produces a sequence of current pulses in a branch circuit that is to be traced to locate an associated circuit interrupter. Each current pulse is of a predetermined duration, a predetermined rise time, and a predefined fall time, which in one embodiment is equal to the current pulse rise time. The receiver is a handheld unit that is positioned in close proximity with the various circuit interrupters of the power distribution system and provides an indication that the desired wire or circuit interrupter has been located upon detecting current pulses that are with a predefined pulse duration, pulse separation and amplitude.

Circuit breaker locator

Voltage measuring instruments and methods of measuring the amplitude of an input signal are disclosed. In an example method of measuring the amplitude of an input signal, in an AC measurement mode, the input signal is coupled through a capacitor, the RMS amplitude of the input signal coupled through the capacitor is determined, and a digital value corresponding to the RMS amplitude is provided. In an automatic measurement mode, the RMS amplitude of the input signal is determined without first coupling the input signal through the capacitor, and a digital value corresponding to the RMS amplitude of the input signal is provided. Further disclosed is a calibration procedure may be used to compensate for any offset of an amplifier of the voltage measuring instrument.

Voltage measurement instrument and method having improved automatic mode operation

An AC/DC voltage measuring instrument is operable in a DC mode, an AC mode, or an automatic mode. In the DC mode, an input terminal is coupled directly to an analog-to-digital converter, which generates a digital output signal indicative of the amplitude of the received signal. In the AC mode, the input terminal is coupled to an RMS circuit through a capacitor. The RMS circuit generates an output signal having an amplitude indicative of the RMS amplitude of the received signal, and this output signal is coupled to the analog-to-digital converter. In the automatic mode, the input terminal is also coupled to the RMS circuit, but it is coupled to the RMS circuit without being coupled through the capacitor. The input terminal is coupled to the RMS circuit through an amplifier, and a calibration procedure is used to compensate for any offset of the amplifier.

A novel method of and apparatus for accurately measuring surge currents such as motor-starting inrush currents is provided. An input signal from a current sensor is monitored, and when the input signal changes and exceeds a predetermined threshold, a surge current is detected. The input signal is acquired over a predetermined time period by a fast sampling ADC, which converts the input signal into a series of digitized samples representative of instantaneous current values. These values are processed to compute average current or RMS current, which is then displayed.

Surge current measurement

A two-terminal multimeter capable of both volt/ohm and current measurement employs an input protection circuit with a positive temperature coefficient impedance and a reference impedance, across which an A-D converter takes measurements. A current measurement signal activates a switch to ground one side of the reference impedance for taking current measurements. A controllable clamping switch grounds the positive temperature coefficient impedance in an input overload situation to provide input protection against damage to the meter components.

Microamp measurement for two-terminal digital meter

An automatic power turn-on circuit for a battery-powered measurement instrument. Instrument power is normally off, and when the instrument is connected to a voltage to be measured, the voltage that is sensed activates an electronic switch that in turn connects an internal battery to the processing and display circuits of the instrument. The voltage sense circuitry includes circuits for sensing either a positive or a negative voltage, and biasing a driver transistor into conduction. The driver transistor in turn activates the switch to connect the battery voltage to a power supply output node. An RC network holds the switch in the &ldquo;on&rdquo; position for a short period of time after the voltage to be measured is removed from the inputs of the instrument.

Automatic power turn-on circuit for a battery-powered voltage measurement apparatus

A voltage indicator using a serial or sequential comparison voltage measurement technique. Reference voltages generated by a voltage divider are applied to inputs of a multiplexer which is driven by a counter to select one reference voltage at a time in sequence to be presented via an output terminal to one input of a voltage comparator. An input signal to be measured is applied the other input of the comparator. When the input signal matches or exceeds the reference voltage at the output terminal of the multiplexer, the comparator switches, providing an enable signal to a one-of-N decoder. The one-of-N decoder is also driven by the counter, so that outputs of the decoder and corresponding inputs of the multiplexer are addressed simultaneously. The outputs of the one-of-N decoder are connected to LEDs which indicate the voltage level or magnitude. The voltage input signal may be applied via a conditioning amplifier that scales the input signal and an absolute value amplifier which provides an output in one polarity for comparison purposes. DC voltage polarity is detected and may be indicated by separate LEDs. Additionally, an AC/DC decode logic circuit may be provided to discern between AC and DC input voltages, and provide appropriate indication. While the preferred embodiment contemplates that both nominal AC and DC reference voltages may be provided by the same voltage divider, a gain control signal may be provided to change the gain of the absolute value amplifier by a ratio of .sqroot.2 so that the same reference values may be used for both AC and DC measurements.

Voltage indicator using serial comparison voltage measurement

A voltage measurement instrument such as a digital multimeter is provided with transient overvoltage input protection. Internal walls are integrally molded with the instrument case and disposed in close proximity to the input receptacles and terminals to separate conductive surfaces and provide transient overvoltage barriers. Top and bottom wall portions are fitted together in tongue-and-groove fashion to increase the creepage and clearance path without increasing the linear distance between conductive surfaces. This arrangement also allows the instrument to maintain a low profile.

Growing community of inventors

Edmonds, WA, United States of America

Michael F Gallavan