Electronic measuring instrument with digital display scale extension

Claim 2

In an electronic measuring system, a meter having a scale of fixed range for the analog display of electrical quantities within said range, an input circuit having a predetermined impedance across said meter, digital displays associated with said scale, electronic sensing means responsive to input magnitudes exceeding said fixed range associated with said circuit, means responsive to the operation of said sensing means for initiating the actuation of certain of said digital displays means for generating in a first path a current representative of the state of the sensing means, and means duplicating the current magnitude in the first path in a second path coupled across the meter in a manner to apply the current in a direction opposite the direction of the current applied to the meter by the input circuit whereby said impedance remains substantially unaltered and said digital display and said analog indication are combined for the measurement of said quantity.

Claim 3

In an electronic measuring system, a meter having a scale of fixed range for the analog display of electrical quantities within said range, an input circuit having a predetermined impedance across said meter, digital displays associated with said scale, electronic sensing means responsive to input magnitudes exceeding said fixed range associated with said circuit, means responsive to the operation of said sensing means for initiating the actuation of certain of said digital displays means for generating in a first path a current representative of the state of the sensing means, and means duplicating the current magnitude in the first path in a second path coupled across the meter in a manner to apply the current in a direction opposite the direction of the current applied to the meter by the input circuit whereby said impedance remains substantially unaltered and said digital display and said analog indication are combined for the measurement of said quantity.

Claim 4

In an electronic measuring system, a meter having a scale of fixed range for the analog display of electrical quantities within said range, an input circuit having a predetermined impedance across said meter, digital displays associated with said scale, electronic sensing means responsive to input magnitudes exceeding said fixed range associated with said circuit, means responsive to the operation of said sensing means for initiating the actuation of certain of said digital displays means for generating in a first path a current representative of the state of the sensing means, and means duplicating the current magnitude in the first path in a second path coupled across the meter in a manner to apply the current in a direction opposite the direction of the current applied to the meter by the input circuit whereby said impedance remains substantially unaltered and said digital display and said analog indication are combined for the measurement of said quantity.

Claim 5

An electronic measuring system in accordance with claim 1 wherein said sensing means comprises a plurality of level detectors connected to said input circuit, said detectors being selectively biased for switching action upon input levels exceeding predetermined magnitudes.

Claim 6

An electronic measuring system in accordance with claim 1 wherein said means for generating comprises a source of fixed potential, and a plurality of parallel current conductive elements in series with said source of fixed potential, each conductive element when conducting initiating a current flow of fixed magnitude in said first path and in said second path, whereby a resulting current is applied across said meter in opposition to the current flow in said meter originating in the input circuit, and switching means selectively controlling said conductive elements in accordance with operation of said sensing means in response to potentials exceeding said range being impressed across said input circuit.

Claim 7

An electronic measuring system in accordance with claim 1 wherein said digital display comprises a glow tube having a common anode and a plurality of cathodes forming numerals, a source of potential for said anode and switching means for each of said cathodes, said switching means being selectively controlled by the operation of said sensing means.

Claim 8

A hybrid display electrical measuring instrument including, in combination: a. a meter having a scale, a pointer and a coil for actuating said pointer, said meter functioning as the analog display of said instrument; b. a gaseous discharge tube having an anode and a plurality of cathodes, each forming a numeral visible upon creating a glow discharge between said anode and any of said cathodes, said discharge tube representing the digital display of said instrument; c. aN input circuit for said instrument including an impedance element and said coil in series between a pair of input terminals, said circuit determining the basic range of said instrument; d. a plurality of operational amplifiers, each having an input circuit effectively connected across said terminals, and an output circuit; e. biasing means for each of said amplifiers predetermining the level of input potential for responsive actuation determining additional ranges of said instrument; f. a switching element associated with each of said cathodes and connected to the output circuit of respective amplifiers for energizing a cathode upon response of an amplifier due to a predetermined level of input potential; g. a source of fixed potential, current conductive means of fixed current magnitude between said input circuit and said source of potential, operable for producing a current flow in said coil in opposition to currents tending to actuate said coil due to input potentials between said terminals exceeding said basic meter range; h. switching means between the output circuit of said operational amplifiers and respective current conductive means for initiating current conductive action in accordance with the operation of any one of said amplifiers at input potentials exceeding said meter range whereby said digital display represents the ranges of said instrument in addition to and beyond said basic range.

Claim 9

A hybrid display electrical measuring instrument including, in combination: a. a meter having a scale, a pointer and a coil for actuating said pointer, said meter functioning as the analog display of said instrument; b. a gaseous discharge tube having an anode and a plurality of cathodes, each forming a numeral visible upon creating a glow discharge between said anode and any of said cathodes, said discharge tube representing the digital display of said instrument; c. aN input circuit for said instrument including an impedance element and said coil in series between a pair of input terminals, said circuit determining the basic range of said instrument; d. a plurality of operational amplifiers, each having an input circuit effectively connected across said terminals, and an output circuit; e. biasing means for each of said amplifiers predetermining the level of input potential for responsive actuation determining additional ranges of said instrument; f. a switching element associated with each of said cathodes and connected to the output circuit of respective amplifiers for energizing a cathode upon response of an amplifier due to a predetermined level of input potential; g. a source of fixed potential, current conductive means of fixed current magnitude between said input circuit and said source of potential, operable for producing a current flow in said coil in opposition to currents tending to actuate said coil due to input potentials between said terminals exceeding said basic meter range; h. switching means between the output circuit of said operational amplifiers and respective current conductive means for initiating current conductive action in accordance with the operation of any one of said amplifiers at input potentials exceeding said meter range whereby said digital display represents the ranges of said instrument in addition to and beyond said basic range.

Claim 10

A hybrid display electrical measuring instrument in accordance with claim 5 wherein operational amplifiers are connected in a regenerative bistable mode for the detection of predetermined input levels.

Claim 11

A hybrid display electrical measuring instrument in accordance with claim 5 wherein said current conductive means comprise the collector current path of a pair of junction transistors having bases tied together and connected to one of the collector electrodes.