Patent ID: 7960979

Claim:
A universal resistance testing device to verify an external resistance, the universal resistance testing device comprising: a bridge circuit having a first branch circuit and a second branch circuit, wherein the first branch circuit includes two removable resistors selected from a plurality of resistors and the second branch circuit includes a single removable resistor selected from the plurality of resistors and a means to electrically connect and disconnect an external resistance having a known resistive value to be verified; a metering circuit having a meter to measure an output of the bridge circuit; a comparator circuit having a plurality of removable resistors; and an output circuit having a transistor, wherein the output circuit receives an electric signal from the comparator circuit and outputs an electric signal to a signaling device to actuate the signaling device, wherein a resistive value of the two removable resistors from the first branch circuit and a resistive value of the single removable resistor of the second branch circuit are known, such that a ratio of the two removable resistors from the first branch circuit is equal to a ratio of the single removable resistor and the known resistive value of the external resistance of the second branch circuit, wherein the two removable resistors in the first branch are interchangeable with two different removable resistors selected from the plurality of resistors that have a different known resistive value than the two removable resistors, and the single removable resistor in the second branch is interchangeable with a different single removable resistor selected from the plurality of resistors that has a different known resistive value than the single removable resistor, and the external resistance is replaceable with a different external resistance having a different known resistive value to be verified than the external resistance, such that a ratio of the two different removable resistors from the first branch circuit is equal to a ratio of the different single removable resistor and the known resistive value of the different external resistance of the second branch circuit, wherein one of the plurality of removable resistors of the comparator circuit is a voltage sensing resistor, and wherein the comparator circuit compares a voltage across the voltage sensing resistor to a reference voltage to verify the resistive value of the external resistance.