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Circuit To Simplify Threshold Adjustments

IP.com Disclosure Number: IPCOM000088691D
Original Publication Date: 1977-Jul-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Seeger, W: AUTHOR

Abstract

This circuit gives an indication when the voltage or current in a power system exceeds or falls below a predetermined percentage from nominal.

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Circuit To Simplify Threshold Adjustments

This circuit gives an indication when the voltage or current in a power system exceeds or falls below a predetermined percentage from nominal.

When the voltage from the sense amplifier on line "A" exceeds the V REF input from point VH in the voltage divider network, the comparator Z1 puts out an "OVER" indication. Likewise when the voltage from the sense amplifier drops below VL in Z2 an "UNDER" indication is obtained. lnput "A" is derived from a sense amplifier with variable gain that normalizes the sensed voltage (or current) to a voltage value VN equal to a fraction of the reference voltage V REF. The values of the resistors in the resistor divider network R1, R2A, R2B, and R3 determine at what percentage above VN or below VN that comparators Z1, Z2 and Z3 will change state. VN is adjusted to the proper value. Comparator Z3 is connected to the junction of R2A and R2B which is referred to as point "B" (VN). The output of Z3 drives a light-emitting diode (LED) 10. When point "A" is below VN, the LED 10 is off. As soon as "A" exceeds VN, the LED 10 will turn on. The circuits are initialized by turning a potentiometer, associated with the sense amplifier variable gain, until the LED 10 just starts to turn on. At this point, the VH and VL thresholds are a given percentage removed from VN.

This circuit improvement eliminates the need for instruments when making adjustments to the circuit. It also eliminates the need for gene...