Fluke Corporation

John Fluke Mfg. Co., Inc.

Raymond D Zoellick

Douglas A Miller

Wilbur R Ames, Iv

Warren H Wong

Peter F Barbee

Jim T Ray

Norbert Werner Jauch

Wilbur R Ames Iv

Warren Haye Wong

Generally described, one or more embodiments of the present disclosure are directed to switch assemblies and methods for switching from one state to another. In some examples, a switch assembly may switch from one electrical contact to another electrical contact by moving a conductive spring or member from a first conductive contact on a printed circuit board (PCB) to a second conductive contact on the PCB. For instance, in one embodiment, a conductive member moves within a slot in the PCB. In another embodiment, a compression force applied to a conductive spring is reduced while the conductive spring moves from a first conductive contact to a second conductive contact.

Electrical switches and methods

A low error, switchable measurement lead detect circuit (,) for providing accurate current measurement readings and reducing susceptibility to false measurement lead detections due to leakage current is described. A gate (,) that receives an input select voltage V,selectively connects either a supply voltage, V,, or ground to the input of a voltage divider (,). V,is connected during a measurement lead detection mode of operation or open fuse detection mode of operation, and a ground is connected during a current measurement mode of operation. During the measurement lead detection mode of operation, if the pin of a measurement lead is present in a split jack (,), the voltage divider (,) divides the supply voltage, V,. Conversely, if no measurement lead pin is present in the split jack (,), the output voltage, V,, of voltage divider (,) equals the level of V,. During open fuse detection mode of operation, a measurement lead is present in the split jack (,), and if a fuse (F,) is present, the voltage divider divides the supply voltage, V,. If a fuse (F,) is not present or is blown, the output voltage, V,, of voltage divider (,) equals the level of V,. During the current measurement mode of operation, the voltage divider (,) and shunt (,) form a series parallel circuit when a measurement lead pin is located in the split jack (,). The impedance of the shunt (,) is negligible in comparison to the impedance of the voltage divider (,), and the voltage drop across shunt (,) is proportional to the injected current. Because the voltage divider (,) is grounded through the gate (,) during the current measurement mode of operation, no error current from supply voltage, V,, passes through the shunt (,). As a result, the accuracy of current measurement readings made during the current measurement mode of operation is improved. Because the supply voltage does not produce an error current during the measurement mode of operation, the overall impedance of the voltage divider (,) can be reduced to reduce susceptibility to leakage current during the measurement lead detection mode of operation.

Low error, switchable measurement lead detect circuit

An improved capacitance measurement system employs a selectable constant current source which is switched into a capacitor in a charge measurement system. The capacitor produces a linear ramp voltage in response to the constant current. An analog-to-digital converter (ADC) measures the change in voltage along the ramp over a corresponding change in time. These values, together with the value of constant current, are used to calculate the capacitance. In the preferred embodiment, a multi-slope ADC is utilized for the measurement. This system offers a wide range of measurable capacitance, and is fast responding and accurate. In addition, visual feedback to the user on measurement progress can be provided, which is particularly advantageous when measuring large capacitors.

Capacitance measurement

An overvoltage and transient protection circuit with extended bandwidth is provided for the protection of a low voltage test signal path (210) such as a test signal path in a multimeter. The disclosed circuit maintains the integrity of a test signal (TS) (114) transmitted by the test signal path (210) by minimizing the effect that unwanted capacitive coupling would otherwise have on the frequency transmission capability of the circuit. During normal operation of the circuit, a test signal path isolation circuit (218) is held between the test signal (TS) (114) and an equivalent buffered guard signal (GS) 227. Held between these equivalent values (TS=GS), no (or minimal) current will be generated in the components of the test signal path isolation circuit (218) as a result of parasitic capacitance. The guard signal (65) (227) is used with guard traces (412) and guard planes (414) to isolate other parts of the test signal path in much the same way. During an overvoltage condition, the test signal path isolation circuit (218) conducts the current resulting from the overvoltage to a clamp circuit (222) that conducts to a voltage limiting circuit. The test signal path (210) may also include a frequency compensated protective resistance (320) that may be relatively high in value.

Low-voltage test signal path protection circuit with extended bandwidth,

An input ranging circuit for an electronic instrument that allows for measuring a.c. voltage, d.c. voltage, and d.c. resistance is provided. The voltage ranging circuit has three modes, d.c. volts, a.c. volts, and ohms, which are selected by a mode switch. A resistor network containing an input resistor, feedback resistors, a reference resistor, and divider resistors provides resistances that are ratiometrically scaled to maintain relatively tight ratio tolerances. A switch array coupled to the resistor network provides for the selected circuit configuration and divider ratio in conjunction with the mode switch. Each of the switches in the switch array may be independently controlled via control signals. In d.c. volts mode, the input voltage is divided down according to a desired voltage divider ratio. In a.c. volts mode, the voltage divider is supplemented with an a.c. amplifier configured to extend the useful bandwidth of the input ranging circuit. In ohms mode, a programmable current scaled according to the ratio of resistances in the resistor network is induced through an unknown resistance and the voltage drop is provided at an ohms sense output.

Input ranging circuit for an electronic instrument

A reference voltage support circuit that interfaces with a variety of reference voltage circuit types including bandgap references, zener references, and reference amplifiers with only the interconnection details being different. The reference voltage support circuit contains a voltage source to produce a stabilized supply current for the reference voltage circuit and a unity gain voltage inverter to produce both positive and negative reference voltages from a unipolar reference voltage circuit. The current source and the unity gain voltage inverter both employ ratiometrically scaled resistor networks coupled to the negative and positive reference voltages for high stability over time and temperature.

Voltage reference support circuit

An isothermal block has a multi-layer thermal conductor interleaves with different layers of a printed circuit board to provide improved thermal coupling of input terminals and a local temperature sensor mounted on the isothermal block. Each of the layers of the thermal conductor is substantially thinner than substrate layers of the printed circuit board. The layers of the thermal conductor are spaced apart from the terminals so as to be electrically isolated from the terminals. Embedded layers of the thermal conductor are spaced closer to the terminals than are external layers of the thermal conductor.

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Bothell, WA, United States of America

Raymond D Zoellick