John Fluke Mfg. Co., Inc.

Fluke Corporation

Other

Benjamin Eng, Jr

John M Anholm, Jr

Peter S Duryee

Margaret E Winsor

John M Lund

Don P Matson

A resistance measuring circuit includes a current generating component, a current control component, and a voltage measurement component. The magnitude of a target resistance can be measured by connecting the target resistance between first and second measurement terminals of the resistance measuring circuit, applying a current generated by the current generating component to the target resistance, and determining the voltage across the target resistance. When no target resistance is connected between the first and second measurement terminals, the current control component controls the current generating component to reduce current consumption of the resistance measuring circuit.

Systems and methods for an open circuit current limiter

Systems and methods for dissipating heat generated during an electrical function are disclosed. In particular, the disclosed systems and methods can be used for dissipating heat generated during low impedance measurement on a multimeter. In some embodiments, the multimeter can include a first thermistor coupled in series with a resistor in a measurement path, a second thermistor, and a switch coupled to the measurement path and the second thermistor for selectively including the second thermistor in the measurement path during a low impedance measurement.

Systems and methods for dissipating heat generated during an electrical measurement

An apparatus and method of measuring capacitances are provided in which charge packets of known value are delivered to a capacitor of unknown value until a final voltage is determined, and the capacitance is calculated based on the known total charge and measured voltage.

Capacitance measurement

A multiple slope integrating analog-to-digital converter (ADC) includes many improvements and refinements which eliminate timing and non-linearity errors which accumulate due to a large number of switching operations that occur over an integrate cycle. The ADC includes an integrator and a comparator in which an input voltage to be measured is applied to a summing node at the input of the integrator during an integrate cycle, while at the same time positive and negative reference currents are selectively applied to the summing node by a controller which monitors the output of the comparator in order to limit the voltage magnitude at the output of the integrator. Thereafter, during a de-integrate cycle, the input voltage is disconnected while progressively shallower ramps are measured with a high-speed clock for greater resolution and accuracy. The comparator has a slight hysteresis built in to slightly separate the switching thresholds for positive-going and negative going ramps. The switches which control selection of the positive and negative reference currents are implemented in such a way that current surges are minimized. A method is provided to control the order in which the switches are operated to eliminate the effects of charge injection due to operation of the switches as well as signals that are cross-coupled from the control lines of adjacent switches. The length of time the respective positive and negative currents are turned on during the integrate cycle is measured, and adjustments may be made using predetermined calibration factors to resolve errors in the ADC system. Thus, circuit parameters and values need only to be stable and not be precise, permitting the use of readily-available and inexpensive off-the-shelf parts and components.

Multiple slope analog-to-digital converter

A miniature high frequency power transformer comprises first and second 'E' shaped ferrite core halves surrounding mating inner and outer modular transformer bobbins having formed thereon respectively the primary and secondary windings of the transformer. The inner and outer modular transformer bobbins are positioned such that the inner transformer bobbin is inserted into the outer transformer bobbin with the secondary windings surrounded by the primary windings. When assembled, the inner modular transformer bobbin has a protrusion that extends axially therefrom through the outer bobbin and terminates in first core retaining ears at one end of the transformer. Second core retaining ears extend from the opposite end of the transformer, and both ears receive the 'E' shaped core halves, maintained in position on the transformer by bonding.

Modular high frequency power transformer

A battery charger supplies to a battery an output voltage having a desired temperature coefficient of voltage. The charger includes an operational amplifier having a summing junction to which a reference current and a feedback signal derived from the amplifier output are supplied. The V.sub.be multiplier circuit includes a bipolar transistor which is biased into its active region so that the charging voltage supplied by the amplifier is temperature corrected in accordance with a negative coefficient of voltage characteristic of the transistor.

Battery charger with Vbe temperature compensation circuit

The ladder network of a recirculation of remainder analog to digital converter has a voltage source that is regulated by a transistor and Zener diode together with feedback circuitry responsive to the regulated output voltage. Current through the circuit is controlled by feedback to establish equal and opposite temperature coefficients in the transistor and Zener diode of the regulator. The temperature stabilized voltage regulator produced thereby eliminates any requirement for trimmer potentiometers.

Precision voltage reference for systems such as analog to digital

In a recirculation of remainder type analog to digital converter, successive remainders recirculated to develop an output digital signal are overlapped to cancel common error components.

Error correcting apparatus for systems such as analog to digital

The ladder network of a recirculation of remainder analog to digital converter has pairs of controlled switches connected alternately to a voltage source and a ground, to establish unidirectional current flow through the switches. Unidirectional current flow eliminates ladder error caused by current flow direction resistances inherent in the switches.

Analog to digital converter using recirculation of remainder

A circuit for supplying regulated first and second supply voltages to the amplifier/comparator of a recirculation of remainder analog to digital converter, comprises a series pair of transistors connected as emitter followers between unregulated voltage sources. Outputs of the emitter followers carry the regulated supply voltages and are applied to the supply terminals of the amplifier/comparator. A pair of diodes connected in series between the bases of the emitter followers establish the magnitudes of the two regulated supply voltages. The junction voltage between the two Zener diodes is controlled by a difference amplifier that in turn is responsive to an analog input voltage and the output of the amplifier/comparator. The output of the difference amplifier causes the regulated supply voltages to track a common mode signal component inherent in the converter and thereby improves component accuracy. Another pair of Zener diodes between the output of the amplifier/comparator and the input to the difference amplifier prevents saturation of the amplifier/comparator by reducing the magnitude of the regulated supply voltages when the amplifier/comparator is in a comparator mode.

Growing community of inventors

Everett, WA, United States of America

Benjamin Eng, Jr