Signal conditioning module for sensing multiform field voltage s

Details Signal conditioning module for sensing multiform field voltage s Signal conditioning module for sensing multiform field voltage s

1997-10-16

1999-06-01

Trammell, James P.

Data processing: measuring, calibrating, or testing

Measurement system

Measured signal processing

702 64, 327309, 327322, G06F 300

Patent

active

059096608

ABSTRACT:
A signal conditioning module for sensing multiform field signals and for providing isolated digital signals appropriate for a processing system. The present invention allows sensing of field signals which are either AC or DC and which have magnitudes ranging from zero to greater than 240 volts in the preferred embodiment. A circuit according to the present invention includes a bidirectional maximum current limiter coupled to a bidirectional isolation current sensor. The current sensor preferably includes an opto-coupler. The current limiter preferably includes cross-coupled depletion mode devices and a current limit resistor. In this manner, current flowing through the resistor develops a voltage for turning off one depletion mode device or the other depending upon the polarity of the current, so that the input current is limited to a predetermined maximum level for a wide voltage range of input signals and regardless of voltage polarity. The opto-coupler preferably includes cross-coupled LEDs for sensing current in either direction. An AC smoothing filter is provided at the output to filter AC signals for providing a smooth digital output signal.

REFERENCES:
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patent: 5083288 (1992-01-01), Somlyody et al.
patent: 5418450 (1995-05-01), Bacon
(1994) IEEE 488 and VXIbus Control, Data Acquisition, and Analysis, SCXI 32-Channel Optically Isolated Digital Input/Output Modules, National Instruments, 1993, pp. 3-161--3 -163. (No date with month).
Grayhill, An ISO-9001 Company, Control Products Catalog, AC Input Module, Grahill Corp., pp. 32, 33, (No date).
Gordos Off-the-Shelf Distributor Catalog, Revised Apr. 1987, DC Input Module, Gordos Corp., pp. 4, 34, 35.

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