Circuit for measuring an unknown resistance by using a voltage ratio

Claim 3

The device as claimed in claim 1 wherein said measurement means includes a. analog to digital converter having input terminal means adapted for reception of said unknown voltage ratio and output terminal means; and b. reference source means AC coupled to said input terminal means for presenting a selected reference signal with respect to a return signal at said input terminal means.

Claim 4

A measuring device comprising: a. first means including first resistor means, said first means adapted for interconnection with second resistor means, said first resistor means having a knOwn resistance value, said second resistor means having an unknown resistance value; and b. analog to digital converter means operatively connected to said first means, said analog to digital converter being a dual slope integrator converter having at least first and second integration periods for charging and discharging integrator means, said analog to digital converter means includes second means AC coupled to said integrator means for selectively applying a reference signal to said integrator means during said second integration period as a function of the polarity of a signal at the output of said integrator means at the end of said first integration period; c. said analog to digital converter operating to measure the resistance value of said second resistor by generating a signal representing the voltage ratio of a voltage across said first resistor means to a voltage across said second resistor means, said voltage ratio being equivalent to the resistance ratio of the resistance value of said first resistor means to the resistance value of said second resistor means.

Claim 5

A measuring device comprising: a. first means including first resistor means, said first means adapted for interconnection with second resistor means, said first resistor means having a knOwn resistance value, said second resistor means having an unknown resistance value; and b. analog to digital converter means operatively connected to said first means, said analog to digital converter being a dual slope integrator converter having at least first and second integration periods for charging and discharging integrator means, said analog to digital converter means includes second means AC coupled to said integrator means for selectively applying a reference signal to said integrator means during said second integration period as a function of the polarity of a signal at the output of said integrator means at the end of said first integration period; c. said analog to digital converter operating to measure the resistance value of said second resistor by generating a signal representing the voltage ratio of a voltage across said first resistor means to a voltage across said second resistor means, said voltage ratio being equivalent to the resistance ratio of the resistance value of said first resistor means to the resistance value of said second resistor means.

Claim 6

A measuring device comprising: a. first means for measuring an unknown resistance including i. first terminal means to which a first voltage is applied, ii. second terminal means, iii. at least one calibrated resistor electrically connected between said first and second terminal means, and iv. third terminal means connected to a return signal, said second and third terminal means adapted for interconnection with a first resistor having an unknown resistance, v. a second voltage of a first value being presented at said second terminal when said second and third terminals are available for reception of said first resistor, vi. A third voltage of a second value being presented at said second terminal means when said first resistor is connected between said second and third terminal means, the voltage ratio of said second voltage to said third voltage being the ratio of the resistance of said first resistor to resistance of said calibrated resistor, b. second means operatively connected to said first means for measuring said voltage ratio; and c. display means electrically communicating with said second means for selectively presenting signals representing the magnitude of said unknown resistance and voltage ratio; d. said second means including an analog to digital converter means having input terminal means adapted for reception of said unknown voltage ratio and output terminal means operatively connected to said display means, and reference source means AC coupled to said input terminal means for presenting a selected reference signal with respect to said return signal at said input terminal means.

Claim 7

A measuring device comprising: a. first means for measuring an unknown resistance including i. first terminal means to which a first voltage is applied, ii. second terminal means, iii. at least one calibrated resistor electrically connected between said first and second terminal means, and iv. third terminal means connected to a return signal, said second and third terminal means adapted for interconnection with a first resistor having an unknown resistance, v. a second voltage of a first value being presented at said second terminal when said second and third terminals are available for reception of said first resistor, vi. A third voltage of a second value being presented at said second terminal means when said first resistor is connected between said second and third terminal means, the voltage ratio of said second voltage to said third voltage being the ratio of the resistance of said first resistor to resistance of said calibrated resistor, b. second means operatively connected to said first means for measuring said voltage ratio; and c. display means electrically communicating with said second means for selectively presenting signals representing the magnitude of said unknown resistance and voltage ratio; d. said second means including an analog to digital converter means having input terminal means adapted for reception of said unknown voltage ratio and output terminal means operatively connected to said display means, and reference source means AC coupled to said input terminal means for presenting a selected reference signal with respect to said return signal at said input terminal means.

Claim 8

A measuring device comprising: a. first means for measuring an unknown resistance including i. first terminal means to which a first voltage is applied, ii. second terminal means, iii. at least one calibrated resistor electrically connected between said first and second terminal means, and iv. third terminal means connected to a return signal, said second and third terminal means adapted for interconnection with a first resistor having an unknown resistance, v. a second voltage of a first value being presented at said second terminal when said second and third terminals are available for reception of said first resistor, vi. A third voltage of a second value being presented at said second terminal means when said first resistor is connected between said second and third terminal means, the voltage ratio of said second voltage to said third voltage being the ratio of the resistance of said first resistor to the resistance of said calibrated resistor, b. second means operatively connected to said first means for measuring said voltage ratio, said second means including i. an analog to digital converter having input terminal means and output terminal means, said input terminal means adapted for recepTion of said unknown voltage ratio, ii. reference source means AC coupled to said input terminal means for presenting a selected reference signal with respect to said return signal at said input terinal means, and iii. third means operatively connected to said analog to digital converter for compensating for an offset voltage of said analog to digital converter, c. display means electrically communicating with said output terminal means for selectively presenting signals representing the magnitude of said unknown resistance and voltage ratio.

Claim 9

A measuring device comprising: a. first means for measuring an unknown resistance including i. first terminal means to which a first voltage is applied, ii. second terminal means, iii. at least one calibrated resistor electrically connected between said first and second terminal means, and iv. third terminal means connected to a return signal, said second and third terminal means adapted for interconnection with a first resistor having an unknown resistance, v. a second voltage of a first value being presented at said second terminal when said second and third terminals are available for reception of said first resistor, vi. A third voltage of a second value being presented at said second terminal means when said first resistor is connected between said second and third terminal means, the voltage ratio of said second voltage to said third voltage being the ratio of the resistance of said first resistor to the resistance of said calibrated resistor, b. second means operatively connected to said first means for measuring said voltage ratio, said second means including i. an analog to digital converter having input terminal means and output terminal means, said input terminal means adapted for recepTion of said unknown voltage ratio, ii. reference source means AC coupled to said input terminal means for presenting a selected reference signal with respect to said return signal at said input terinal means, and iii. third means operatively connected to said analog to digital converter for compensating for an offset voltage of said analog to digital converter, c. display means electrically communicating with said output terminal means for selectively presenting signals representing the magnitude of said unknown resistance and voltage ratio.

Claim 10

The measuring device as claimed in claim 5 wherein said analog to digital converter is a dual slope integrator analog to digital converter which includes: a. first switch means having opened and closed switching states; b. second switch means having opened and closed switching states, said first and second switch means being a series-shunt switch pair; c. integrator means having inverting terminal means, non-inverting terminal means and output terminal means, said first switch means operatively connected between said input terminal means and said inverting terminal means, said second switch means operatively connected between said inverting terminal means and said return signal, said reference source AC coupled to said inverting terminal means, d. third means operatively connected to said first and second switch means for controlling the switching state of said first and second switch means; e. said first switch means being in a closed switching state and said second switch means being in an opened switching state during a first portion of a conversion cycle, said first switch means being in an opened switching state during a second portion of said conversion cycle, said integrator charged for a specified time during said first portion of said conversion cycle and discharged during said second portion of said conversion cycle; and f. comparator means having first and second input terminal means and output terminal means, said compensating means operatively connected between said comparator output terminal means and said noninverting terminal means, said comparator first input terminal means electrically communicating with said integrator output terminal means, said comparator output terminal means operatively connected to said reference source means for determining the selected voltage presented at said inverting terminal means as a function of the polarity of a signal presented at said comparator output terminal means at the end of said first portion of said conversion cycle, a signal at said output terminal means of said comparator means being approximately zero at the end of said second portion of said conversion cycle.

Claim 11

The measuring device as claimed in claim 6 wherein said reference source means includes: a. first reference terminal means adapted for reception of a first signal; b. second reference terminal means; c. third reference terminal means connected to said return signal; d. first resistor means connected between said first and second reference terminal means; e. second resistor means connected between said second and third reference terminal means; f. the ohmic value of said first and second resistor means being such that the magnitude of a second signal applied to said second reference terminal means is approximately one half the magnitude of said first signal; g. first capacitor means having first and second terminal means, said first capacitor second terminal means operatively connected to said inverting terminal means; h. first reference switch means having opened and closed switching states, said first reference switch means connected between said first capacitor first terminal means; i. second reference switch means having opened and closed switching states, said second reference switch means connected between said second reference terminal means and said first capacitor first terminal means; j. third reference switch means having opened and closed switching states, said third reference switch means connected between said second reference terminal means and said first capacitor first terminal means; and k. fourth means operatively connected to said first, second and third reference switch means for controlling the switching states of said first, second and third reference switch means; l. said second reference switch means being in a closed switching state during said first portion of said second portion of said conversion cycle; m. said first and third reference switch means being in an opened switching state during said first portion of said conversion cycle; n. said first reference switch means being in a closed switching state if said signal presented at said comparator output terminal means at the end of said first portion of said conversion cycle is a first polarity, said first reference switch means being in an opened switching state during said second portion of said conversion cycle if said signal presented at said comparator output terminal means at the end of said first portion of said conversion cycle is a second polarity which is oppposite said first polarity; o. said third reference switch means being in a closed switching state during said second portion of said conversion cycle if said signal presented at said comparator output terminal means at the end of said first portion of said conversion cycle is said second polarity, said third reference switch means being in an opened switching state if said signal presented at said comparator output terminal means at the end of said first portion of said conversion cycle is said first polarity; p. a first reference signal with respect to said return signal is applied to said non-inverting terminal means when said signal presented at said comparator output terminal means at the end of said first portion of said conversion cycle is said first polarity, a second reference signal with respect to said return signal is applied to said non-inverting terminal means when said signal presented at said comparator output terminal means at the end of said first portion of said conversion cycle is said second polarity, said first and second reference signals having opposite polarities.

Claim 12

The measuring device as claimed in claim 7 wherein said compensating means includes: a. second capacitor serially connected between said non-inverting terminal means and said return; and b. compensating switch means having opened and closed switching states, said compensating switch means serially connected between said comparator output terminal means and said non-inverting terminal means; c. said compensating switch means being in an opened switching state during said conversion cycle, said compensating switch means being in a closed switching state between conversion cycles; d. said second capacitor being charged to an offset voltage when said compensating switch means is in a closed switching state, said offset voltage stored on said second capacitor being presented at said non-inverting terminal means during said conversion cycle.

Claim 13

A measuring device comprising: a. means for measuring an unknown resistance; b. means for measuring an unknown voltage ratio including i. an analog to digital converter having input terminal means adapted for reception of said unknown voltage ratio and output terminal means; ii. reference source means AC coupled to said input terminal means for presenting a selected reference signal at said input terminal means; and iii. means operatively connected to said analog to digital converter for compensating for an offset voltage of said analog to digital converter; and c. diaplay means electrically communicating with said means for measuring an unknown resistance and said means for measuring an unknown voltage ratio for selectively presenting signals representing the magnitude of said unknown resistance and voltage.

Claim 14

A measuring device comprising: a. means for measuring an unknown resistance; b. means for measuring an unknown voltage ratio including i. an analog to digital converter having input terminal means adapted for reception of said unknown voltage ratio and output terminal means; ii. reference source means AC coupled to said input terminal means for presenting a selected reference signal at said input terminal means; and iii. means operatively connected to said analog to digital converter for compensating for an offset voltage of said analog to digital converter; and c. diaplay means electrically communicating with said means for measuring an unknown resistance and said means for measuring an unknown voltage ratio for selectively presenting signals representing the magnitude of said unknown resistance and voltage.

Claim 15

The measuring device as claimed in claim 9 wherein said analog to digital converter is a dual slope integrator analog to digital converter which includes: a. first switch means having opened and closed switching states; b. second switch means having opened and closed switching states, said first and second switch means being a series-shunt switch pair; c. integrator means having inverting terminal means, non-inverting terminal means and output terminal means, said first switch means operatively connected between said input terminal means and said inverting terminal means, said second switch means operatively connected between said inverting terminal means and a return, said bipolar reference source AC coupled to said inverting terminal means, d. first means operatively connected to said first and second switch means for controlling the switching state of said first and second switch means; e. said first switch means being in a closed switching state and said second switch means being in an opened switching state during a first portion of a conversion cycle, said first switch means being in an opened switching state and said second switch means in a closed switching state during a second portion of said conversion cycle, said integrator charged for a specified time during said first portion of said conversion cycle and discharged during said second portion of said conversion cycle; and f. comparator means having first and second input terminal means and output terminal means, said compensating means operatively connected between said comparator output terminal means and said non-inverting terminal means, said comparator second input terminal means connected to said return said comparator first input terminal means electrically communicating with said integrator output terminal means, said comparator output terminal means operatively connected to said bipolar reference source means for determining the selected voltage presented at said inverting terminal means as a function of the polarity of a signal presented at said comparator terminal means at the end of said first portion of said conversion cycle a signal at said output terminal means of said comparator means being approximately zero at the end of said second portion of said conversion cycle.

Claim 16

The measuring device as claimed in claim 10 wherein said bipolar reference source means includes: a. first reference terminal means adapted for reception of a first reference voltage; b. second reference terminal means; c. third reference terminal means connected to said return; d. first resistor means connected between said first and second reference terminal means; e. second resistor means connected between said second and third reference terminal means; f. the ohmic value of said first and second resistor means being such that the magnitude of a second reference voltage at said second reference terminal means is approximately one half the magnitude of said first reference voltage; g. first capacitor means having first and second terminal means, said first capacitor second terminal means operatively connected to said inverting terminal means. h. first reference switch means having opened and closed switching states, said first reference switch means connected between said first reference terminal means and said first capacitor first terminal means; i. second reference switch means having opened and closed switching states, said second reference switch means connected between said second reference terminal means and said first capacitor first terminal means; and j. third reference switch means having opened and closed switching states, said third reference switch means connected between said second reference terminal means and said first capacitor first terminal means; and k. second means operatively connected to said first, second and third reference switch means for controlling the switching states of said first, second and third refereNce switch means; l. said second reference switch means being in a closed switching state during said first portion of said conversion cycle and in an opened switching state during said second portion of said conversion cycle; m. said first and third reference switch means being in an opened switching state during said first portion of said conversion cycle; n. said first reference switch means being in a closed switching state during said second portion of said conversion cycle if said signal presented at said comparator output terminal means at the end of said first portion of said conversion cycle is a first polarity, said first reference switch means being in an opened switch state during said second portion of said conversion if said signal presented at said comparator output terminal means at the end of said first portion of said conversion cycle is a second polarity which is opposite said first polarity; o. said third reference switch means being in a closed switching state during said second portion of said conversion cycle if said signal presented at said comparator output terminal means at the end of said first portion of said conversion cycle is said second polarity, said third reference switch means being in an opened switching state if said signal presented at said comparator output terminal means at the end of said first portion of said convernsion cycle is said first polarity.

Claim 17

The measuring device as claimed in claim 11 wherein said compensating means includes: a. second capacitor serially connected between said non-inverting terminal means and said return; and b. compensating switch means having opened and closed switching states, said compensating switch means serially connected between said comparator output terminal means and said non-inverting terminal means; c. said compensating switch means being in an opened switching state during said conversion cycle, said compensating switch means being in a closed switching state between conversion cycles; d. said second capacitor being charged to an offset voltage when said compensating switch means is in a closed switching state, said offset voltage stores on said second capacitor being presented at said non-inverting terminal means during said conversion cycle.

Claim 18

The measuring device as claimed in claim 12, wherein said means for measuring an unknown resistance includes: a. first terminal means to which a first voltage is applied, b. second terminal means, c. at least one calibrated resistor electrically connected between said first and second terminal means, and d. third terminal means connected to a return, said second and third terminal means adapted for interconnection with a first resistor having an unknown resistance, e. a second voltage of a first value being presented at said second terminal when said second and third terminals are available for reception of said first resistor, f. a third voltage of a second value being presented at said second terminal when said first resistor is connected between said second and third terminal means, the ratio of said second voltage to said third voltage being the ratio of the resistance of said first resistor to the resistance of said calibrated resistor.

Claim 19

A digital multimeter comprising: a. means for measuring an unknown resistance including i. first terminal means to which a first voltage is applied, ii. second terminal means, iii. at least one calibrated resistor electrically connected between said first and second terminal means, and iv. third terminal means connected to a return, said second and third terminal means adapted for interconnection with a first resistor having an unknown resistance, v. a second voltage of a first value being presented at said second terminal when said second and third terminals are available for reception of said first resistor, vi. a third voltage of a second value being presented at said second terminal When said first resistor is connected between said second and third terminal means, the ratio of said second voltage to said third voltage being the ratio of the resistance of said first resistor to the resistance of said calibrated resistor, b. dual slope analog to digital converting means for measuring an unknown voltage ratio including i. integrator means having first and second input terminal means and output terminal means, said integrator means being charged for a present time to a first voltage during a first portion of a conversion cycle, said integrator being discharged during a second portion of said conversion cycle, ii. comparator means having first and second input terminal means and output terminal means, said first comparator input terminal means connected to said integrator output terminal means, said second comparator means input terminal means connected to a return iii. first switching means operatively connected to said integrator means first input terminal means for controlling a signal applied to said integrator first input terminal means, iv. first control means operatively connected to said first switching means for control thereof, v. clock means for generating a series of timing pulses, said clock means operatively connected to said control means, c. bipolar reference source means AC coupled to said integrator means first input terminal means for presenting a selected voltage at said integrator means first input terminal means; d. compensating means operatively connected between said comparator output terminal means and said integrator means second input terminal means for compensating for an offset voltage of said integrator means; e. display means electrically communicating with said means for measuring an unknown resistance and said means for measuring an unknown voltage ratio for selectively presenting signals representing the magnitude of said unknown resistance and voltage; and f. second control means operatively connected between said display means and said means for measuring an unknown resistance and means for measuring an unknown voltage ratio, said second control means operating to selectively apply signals generated by said means for measuring an unknown resistance and means for measuring an unknown voltage ratio to said display means for presentation.

Claim 20

A digital multimeter comprising: a. means for measuring an unknown resistance including i. first terminal means to which a first voltage is applied, ii. second terminal means, iii. at least one calibrated resistor electrically connected between said first and second terminal means, and iv. third terminal means connected to a return, said second and third terminal means adapted for interconnection with a first resistor having an unknown resistance, v. a second voltage of a first value being presented at said second terminal when said second and third terminals are available for reception of said first resistor, vi. a third voltage of a second value being presented at said second terminal When said first resistor is connected between said second and third terminal means, the ratio of said second voltage to said third voltage being the ratio of the resistance of said first resistor to the resistance of said calibrated resistor, b. dual slope analog to digital converting means for measuring an unknown voltage ratio including i. integrator means having first and second input terminal means and output terminal means, said integrator means being charged for a present time to a first voltage during a first portion of a conversion cycle, said integrator being discharged during a second portion of said conversion cycle, ii. comparator means having first and second input terminal means and output terminal means, said first comparator input terminal means connected to said integrator output terminal means, said second comparator means input terminal means connected to a return iii. first switching means operatively connected to said integrator means first input terminal means for controlling a signal applied to said integrator first input terminal means, iv. first control means operatively connected to said first switching means for control thereof, v. clock means for generating a series of timing pulses, said clock means operatively connected to said control means, c. bipolar reference source means AC coupled to said integrator means first input terminal means for presenting a selected voltage at said integrator means first input terminal means; d. compensating means operatively connected between said comparator output terminal means and said integrator means second input terminal means for compensating for an offset voltage of said integrator means; e. display means electrically communicating with said means for measuring an unknown resistance and said means for measuring an unknown voltage ratio for selectively presenting signals representing the magnitude of said unknown resistance and voltage; and f. second control means operatively connected between said display means and said means for measuring an unknown resistance and means for measuring an unknown voltage ratio, said second control means operating to selectively apply signals generated by said means for measuring an unknown resistance and means for measuring an unknown voltage ratio to said display means for presentation.

Claim 21

The digital multimeter as claimed in claim 14 wherein said bipolar reference source means includes: a. first reference terminal means adapted for reception of a first reference voltage; b. second reference terminal means; c. third reference terminal means connected to said return; d. first resistor means connected between said first and second reference terminal means; e. second resistor means connected between said second and third reference terminal means; f. the ohmic value of said first and second resistor means being such that the magnitude of a second reference voltage at said second reference terminal means is approximately one half the magnitude of said first reference voltage; g. first capacitor means having first and second terminal means said first capacitor second terminal means operatively connected to said integrator means second input terminal means; h. first reference switch means having opened and closed switching states, said first reference switch means connected between said first reference terminal means and said first capacitor first terminal means; i. second reference switch means having opened and closed switching states, said second reference switch means connected between said second reference terminal means and said first capacitor first terminal means; and j. third reference switch means having opened and closed switching states, said third reference switch means connected between said second reference terminal means and said first capacitor first terminal means; and k. third means operatively connected to said first, second and third reference switch means for controlling the switching states of said first, second and third reference switch means; l. said second reference switch means being in a closed switching state during said first portion of said conversion cycle and in an opened switching state during said second portion of said conversion cycle. m. said first and third reference switch means being in an opened switching state during said first portion of said conversion cycle; n. said first reference switch means being in a closed switching state during said second portion of said conversion cycle if said signal at said comparator output terminal means at the end of said first portion of said conversion cycle is a first polarity, said first reference switch means being in an opened switching state during said second portion of said conversion if said signal presented at said comparator output terminal means at the end of said first portion of said conversion cycle is a second polarity which is opposite said first polarity; o. said third reference switch means being in a closed switching state during said second portion of said conversion cycle if said signal presented at said comparator output terminal means at the end of said first portion of said conversion cycle is in said second polarity, said third reference switch means being in an opened switching state of said signal presented at said comparator output terminal means at the end of said first portion of said conversion cycle is said first polarity.