# US 7,098,648 B2 · Automatic range finder for electric current testing

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- Number: US 7,098,648 B2
- Document ID: US7098648B2
- Status: Granted
- Kind: B2
- Application number: 10/868,520
- Filed: 2004-06-14
- Published: 2005-09-22
- Granted: 2006-08-29
- Earliest claimed: 2004-03-16
- Assignees: QualiTau, Inc.
- Inventors: Gedaliahoo Krieger; Peter P. Cuevas; James Borthwick
- Web page: https://patentgrep.com/patent/US7098648B2

## CPC

- G01R 19/16561: {in hand-held circuit testers (see also G01R19/155)}
- G01R 15/09: Autoranging circuits
- G01R 19/0092: {Measuring current only}
- G01R 19/1659: {to indicate that the value is within or outside a predetermined range of values (window) (G01R19/16514, G01R19/16519, G01R19/16528 and G01R19/16533 take precedence)}
- G01R 31/2608: {for testing bipolar transistors}
- G01R 31/2621: {for testing field effect transistors, i.e. FET's}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

In an electrical circuit for testing electrical current using a plurality of precision resistors connected in parallel or in series, a range finder for receiving the current to be measured with the voltage drop across the range finder being indicative of a current sub-range for measurement. In a preferred embodiment, a range finder has a first bipolar transistor and a second bipolar transistor connected in parallel and in opposite polarity with the emitter and base of each transistor connected together whereby each transistor functions as an emitter-base diode.

## Claims

### Claim 1

A current measurement circuit comprising:
a) a resistor network including a plurality of resistors selectively connectable for receiving a range of current to be measured, a voltage drop across a resistor being indicative of current, each resistor correesponding to a sub-range of current to be measured,
b) a range finder selectively connectable for receiving the current to be measured, the voltage drop across the range finder being indicative of a sub-range of current, and
c) a switch control circuit responsive to voltage drop across the range finder and controlling the connection of the plurality of resistors for receiving the sub-range of current to be measured.

### Claim 2 (depends on 1)

The current measurement circuit as defined by claim 1 wherein the range finder comprises a diode sensor.

### Claim 3 (depends on 2)

The current measurement circuit as defined by claim 2 wherein the diode sensor comprises a first transistor and a second transistor connected in parallel with each transistor being diode connected.

### Claim 4 (depends on 3)

The current measurement circuit as defined by claim 3 wherein the first transistor and the second transistor are bipolar transistors with collector and base of each transistor being ohmically connected.

### Claim 5 (depends on 4)

The current measurement circuit as defined by claim 4 wherein the bipolar transistors are npn bipolar transistors.

### Claim 6 (depends on 3)

The current measurement circuit as defined by claim 3 wherein the resistor network comprises a plurality of precision resistors connectable in parallel.

### Claim 7 (depends on 3)

The current measurement circuit as defined by claim 3 wherein the resistor network comprises a plurality of serially connected precision resistors with each resistor having a switchable low ohmic shunt connector.

### Claim 8 (depends on 1)

The current measurement circuit as defined by claim 1 wherein the resistor network comprises a plurality of precision resistors connectable in parallel.

### Claim 9 (depends on 1)

The current measurement circuit as defined by claim 1 wherein the resistor network comprises a plurality of serially connected precision resistors with each resistor having a switchable low ohmic shunt connector.