Ohmmeter for measuring the internal resistance of a battery and directly reading the measured resistance value

Claim 2

An ohmmeter for measuring the internal resistance of a battery comprising a DC power source circuit; a DC constant voltage circuit for producing a DC constant voltage output from the DC power of said DC power source circuit, a DC-AC conversion circuit for converting said DC constant voltage output to an AC constant current having a relatively high frequency; said DC constant voltage circuit being a series-type constant voltage circuit comprising a control transistor having a collector connected to one output terminal of said DC power source circuit, an emitter connected to one input terminal of said DC-AC conversion circuit, and a base connected to said one output terminal of said DC power source circuit through a resistor; and a reference transistor having an emitter connected to the base of said control transistor and a base connected to the other output terminal of said DC power source circuit through a constant voltage diode and also to said one output terminal of said DC power source circuit through another resistor; a DC blocking device, said AC constant current being applied to a battery to be measured through said DC blocking device, said DC blocking device preventing DC current from flowing from the battery; and an AC voltmeter circuit including an indicatOr connected across the battery for measuring the AC voltage drop of the battery due to its internal resistance, said indicator of said AC voltmeter circuit being adapted to indicate directly the internal resistance of the battery.

Claim 3

An ohmmeter for measuring the internal impedance of a battery according to claim 1 wherein said control transistor and reference transistor have the same temperature characteristic with respect to the voltage across the emitter and base thereof, and one of said transistors is of PNP type and the other of said transistor is of NPN type.

Claim 4

An ohmmeter for measuring the internal resistance of a battery comprising a DC power source circuit; a DC constant voltage circuit for producing a DC constant voltage output from the DC power of said DC power source circuit; a DC-AC conversion circuit for converting said DC constant voltage output to an AC output of a constant current having a sine wave of a predetermined frequency, said DC-AC conversion circuit including means for maintaining the current and voltage of said AC output at constant; and further comprising means for converting the DC voltage to an AC voltage, said converting means including an oscillation transformer having a secondary coil for producing said AC constant current and a control circuit connected in circuit between said DC constant voltage circuit and said converting means for controlling said DC constant voltage produced by said DC constant voltage circuit in accordance with a feed-back current and a feed-back voltage supplied from said converting means thereby applying the controlled DC constant voltage to said converting means; current feed-back means including a first circuit connected between said secondary coil and the battery to be measured for taking out a current component relating to said AC constant current applied to said battery, and a rectifying circuit connected between said first circuit and said control circuit for producing said feed-back current by rectifying said current component; and voltage feed-back means including a third coil of said oscillation transformer for taking out a voltage component proportional to a voltage induced to said secondary coil, and a rectifying circuit connected between said third coil and said control circuit for producing said feed-back voltage by rectifying said voltage component; a DC blocking device, said AC constant current being applied to a battery to be measured through said DC blocking device, said DC blocking device preventing DC current from flowing from the battery; and an AC voltmeter circuit including an indicator connected across the battery for measuring the AC voltage drop of the battery due to its internal resistance, said indicator of said AC voltmeter circuit being adapted to indicate directly the internal resistance of the battery.

Claim 5

An ohmmeter for measuring the internal resistance of a battery comprising a DC power source circuit; a DC constant voltage circuit for producing a DC constant voltage output from the DC power of said DC power source circuit; a DC-AC conversion circuit for converting said DC constant voltage output to an AC output of a constant current having a sine wave of a predetermined frequency, said DC-AC conversion circuit including means for maintaining the current and voltage of said AC output at constant; and further comprising means for converting the DC voltage to an AC voltage, said converting means including an oscillation transformer having a secondary coil for producing said AC constant current and a control circuit connected in circuit between said DC constant voltage circuit and said converting means for controlling said DC constant voltage produced by said DC constant voltage circuit in accordance with a feed-back current and a feed-back voltage supplied from said converting means thereby applying the controlled DC constant voltage to said converting means; current feed-back means including a first circuit connected between said secondary coil and the battery to be measured for taking out a current component relating to said AC constant current applied to said battery, and a rectifying circuit connected between said first circuit and said control circuit for producing said feed-back current by rectifying said current component; and voltage feed-back means including a third coil of said oscillation transformer for taking out a voltage component proportional to a voltage induced to said secondary coil, and a rectifying circuit connected between said third coil and said control circuit for producing said feed-back voltage by rectifying said voltage component; a DC blocking device, said AC constant current being applied to a battery to be measured through said DC blocking device, said DC blocking device preventing DC current from flowing from the battery; and an AC voltmeter circuit including an indicator connected across the battery for measuring the AC voltage drop of the battery due to its internal resistance, said indicator of said AC voltmeter circuit being adapted to indicate directly the internal resistance of the battery.

Claim 6

An ohmmeter for measuring the internal resistance of a battery comprising: A DC power source circuit; a DC constant voltage circuit including a first control transistor connected in series between said DC power source and a voltage control circuit for producing a DC constant voltage from the DC power of said DC power source circuit; a DC-AC conversion circuit comprising said DC voltage control circuit and an oscillation circuit, said DC voltage control circuit including a second control transistor connected in series between said DC constant voltage circuit and said oscillation circuit for controlling said DC constant voltage thereby supplying said oscillation circuit with a DC controlled voltage, and said oscillation circuit including a pair of push-pull connected output transistors for converting said DC controlled voltage to an AC controlled voltage and a transformer having a primary winding connected to said pair of output transistors and a secondary winding for producing an AC output voltage proportional to said AC controlled voltage; connecTing means for connecting said secondary winding to a battery to be measured, said means including a DC blocking device for preventing DC current from flowing from said connected battery and terminal means including current and voltage terminals for supplying said connected battery with a current from said output voltage of said secondary winding through said current terminals and takingout the voltage drop of said connected battery through said voltage terminals; means for detecting variation of said current supplied to said battery through said connecting means and applying a signal relating to said variation to said second control transistor for controlling the same; and indicator means comprising an AC amplifier connected to said voltage terminals for amplifying said voltage drop of said battery and an indicator circuit including a rectifier and an indicator connected to said amplifier through said rectifier for indicating directly the internal resistance of said battery by measuring said amplified voltage drop after rectification.

Claim 7

An ohmmeter for measuring the internal resistance of a battery comprising: A DC power source circuit; a DC constant voltage circuit including a first control transistor connected in series between said DC power source and a voltage control circuit for producing a DC constant voltage from the DC power of said DC power source circuit; a DC-AC conversion circuit comprising said DC voltage control circuit and an oscillation circuit, said DC voltage control circuit including a second control transistor connected in series between said DC constant voltage circuit and said oscillation circuit for controlling said DC constant voltage thereby supplying said oscillation circuit with a DC controlled voltage, and said oscillation circuit including a pair of push-pull connected output transistors for converting said DC controlled voltage to an AC controlled voltage and a transformer having a primary winding connected to said pair of output transistors and a secondary winding for producing an AC output voltage proportional to said AC controlled voltage; connecTing means for connecting said secondary winding to a battery to be measured, said means including a DC blocking device for preventing DC current from flowing from said connected battery and terminal means including current and voltage terminals for supplying said connected battery with a current from said output voltage of said secondary winding through said current terminals and takingout the voltage drop of said connected battery through said voltage terminals; means for detecting variation of said current supplied to said battery through said connecting means and applying a signal relating to said variation to said second control transistor for controlling the same; and indicator means comprising an AC amplifier connected to said voltage terminals for amplifying said voltage drop of said battery and an indicator circuit including a rectifier and an indicator connected to said amplifier through said rectifier for indicating directly the internal resistance of said battery by measuring said amplified voltage drop after rectification.

Claim 8

An ohmmeter according to claim 4, wherein said DC power source circuit includes a battery as a DC power source and said DC blocking device includes a non-polarized capacitor.

Claim 9

An ohmmeter according to claim 4, wherein said AC amplifier of said indicator means includes an input transistor having a collector connected to ground thereby providing a large input impedance, an output transistor having an emitter connected to ground through a low AC impedance thereby providing a high amplification factor and negative feedback means including a resistance element having a negative temperature coefficient for connecting the collector of said output transistor to the emitter of said input transistor.

Claim 10

An ohmmeter accordingto claim 4, wherein said terminal means includes a pair of said current terminals adapted to be connected across said battery to be measured and a pair of said voltage terminals adapted to take out the voltage drop of said connected battery.