Method of and apparatus for accurate resistance measurement with a programmable current source
AssigneeMicroLogic, Inc.
InventorsDaniel B. Kotlow, Carlos A. Barberis
Life of this patent
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Abstract
Remote resistance measurement technique using a programmable current source to enable accurate measurement of resistance, such as physical parameter sensing resistors such as for the remote monitoring of vehicular construction equipment or the like, particularly where full physical access to the sense resistor is not possible, as, for example, in vehicular fuel gauge applications and the like.
Claims33
A method of accurately measuring the varying resistance of a sensing resistor, that comprises, alternately applying from a programmable current source pairs of different currents to each of a sensing resistor and a standard reference resistor to develop corresponding pairs of different voltages;
- subtracting the different voltages of the respective pairs of different voltages;
- subtracting the different currents of the respective pairs of currents applied to the respective resistors;
- and taking the ratio of the subtracted pairs of different voltages each divided by the corresponding subtracted differences in the currents of the respective pairs of currents, wherein the currents applied to the sensing resistor are applied through an offset resistor and wherein the location of the sensing resistor is in equipment such as vehicular equipment that does not permit full physical access to both terminals of the sensing resistor, and wherein the sensing resistor comprises a parameter-measuring resistance, the ground terminal of which is in an equipment location not easily accessible.
A method of accurately measuring the varying resistance of a sensing resistor, that comprises, alternately applying from a programmable current source pairs of different currents to each of a sensing resistor and a standard reference resistor to develop corresponding pairs of different voltages;
- subtraction the different voltages of the respective pairs of different voltages;
- subtraction the different currents of the respective pairs of currents applied to the respective resistors;
- and taking the ratio of the subtracted pairs of different voltages each divided by the corresponding subtracted differences in the currents of the respective pairs of currents, wherein the currents applied to the sensing resistor are applied thorough an offset resistor and wherein one pair of said different currents i1 and i2 enabling measurements of the sensing resistor (R) develops a pair of respective voltages V1 and V2 that, when subtracted, provides the result given by equation (I) herein, where (ROFF) is said offset resistor.
Resistance measurement apparatus for accurately measuring the varying resistance of a sensing resistor having, in combination, a microprocessor controlled programmable current source;
- switching circuit for alternately applying pairs of different currents from the source to each of a sensing resistor and a standard reference resistor to develop corresponding pairs of different voltages;
- the processor enabling subtracting the different voltages of the respective pairs of different voltages and subtracting the different currents of the respective pairs of currents applied to the respective resistors;
- and the Processor further enabling taking the ratio of the subtracted pairs of different voltages each divided by the corresponding subtracted differences in the currents of the respective pairs of currents, wherein the location of the sensing resistor is in equipment such as vehicular equipment that does not permit full physical access to both terminals of the sensing resistors, and wherein the sensing resistor comprises a parameter-measuring resistance, the pound terminal of which is in an inaccessible location of the equipment.
Dependencies are inferred from the claim text.