Digital voltmeter
First Claim
1. A digital voltage measuring instrument for providing a display of the magnitude of an analog voltage signal, comprising:
- input terminal means for operatively connecting an input analog voltage to be measured to a metering circuit,said metering circuit comprising a signal conditioning circuit having impedance means to attenuate voltage transients and overloads for protection of the metering circuit and gain adjust said input voltage,a VAC/VDC control circuit connected to said signal conditioning circuit for automatically detecting whether said input voltage is an AC or DC voltage, and generating control signals indicating the current-type of the input voltage as well as controlling the measurement of said voltage, said control circuit having a zero-cross detecting means including a comparator to which said input voltage is supplied and a peak to peak rectifier coupled to said comparator,an A/D converter having inputs from said signal conditioning circuit and said VAC/VDC control circuit supplied thereto so as to generate digital output signals indicative cf the magnitude of said input voltage,the A/D converter of said metering circuit being operatively connected to a display means to receive said digital output signals and visually display them in a readable form.
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Accused Products
Abstract
A voltage measuring instrument which generally includes signal conditioning circuitry coupled to input probes for protection against overvoltages and processing of input voltage signals. A VAC/VDC control circuit will determine whether AC or DC voltages are present, and will positively indicate when no voltage is present in a test circuit. The metering circuit of the invention will thereby automatically determine the proper mode of operation for the type of voltage present in a test circuit so as to eliminate user selection of operating parameters and possible errors. Further, the metering circuit is adapted to generate a proper reference voltage for the measured voltage automatically, to again eliminate selection of a voltage range by the user. A power supervision circuit is adapted to automatically shut off the measuring instrument after a predetermined amount of time has elapsed, and will automatically shut off power in the event that available battery power drops below a given level. There may be additionally provided a true RMS measuring circuit and a continuity measuring circuit which may be automatically implemented. The voltmeter provides an instrument which is substantially insensitive to effects of distributive capacitance within a test circuit, and provides a safe, easy to operate and versatile measuring instrument.
73 Citations
19 Claims
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1. A digital voltage measuring instrument for providing a display of the magnitude of an analog voltage signal, comprising:
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input terminal means for operatively connecting an input analog voltage to be measured to a metering circuit, said metering circuit comprising a signal conditioning circuit having impedance means to attenuate voltage transients and overloads for protection of the metering circuit and gain adjust said input voltage, a VAC/VDC control circuit connected to said signal conditioning circuit for automatically detecting whether said input voltage is an AC or DC voltage, and generating control signals indicating the current-type of the input voltage as well as controlling the measurement of said voltage, said control circuit having a zero-cross detecting means including a comparator to which said input voltage is supplied and a peak to peak rectifier coupled to said comparator, an A/D converter having inputs from said signal conditioning circuit and said VAC/VDC control circuit supplied thereto so as to generate digital output signals indicative cf the magnitude of said input voltage, the A/D converter of said metering circuit being operatively connected to a display means to receive said digital output signals and visually display them in a readable form. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification