Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Plural ranges – scales or registration rates
Patent
1987-09-21
1989-02-14
Smith, Jerry
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Plural ranges, scales or registration rates
324157, G01R 104, G01R 3136
Patent
active
048049085
ABSTRACT:
A digital voltage and continuity test instrument for use by electricians is disclosed. AC, DC and continuity test functions are provided with the AC and DC test modes including auto-zeroing. In a continuity test mode the continuity of the probe leads or the continuity of a circuit may be detected and indicated with a zero-display value. With the probes open circuit in the continuity mode the display provides a reading proportionate to the battery voltage level of the instrument. The electrical test circuitry includes a resistive divider network connected between the test probes, an AC rectifier for demodulating AC voltages received from the resistor divider network and an analog to digital convertor for receiving DC voltages from the resistive divider network or from the demodulator for driving the display according to the magnitude of the received voltage. Strain relief is provided for the test leads and includes an eyelet having a first washer-like end and a second tubular portion for receiving a test lead. The tubular portion is crimped on the lead and the conductor is soldered thereto. The eyelet is positioned within the housing with the washer-like end is positioned near the housing lead aperture so that stress applied to the lead is applied to the inside of the housing through the eyelet.
REFERENCES:
patent: 1387907 (1921-08-01), Recker
patent: 2703872 (1955-03-01), Doane
patent: 2791748 (1957-05-01), Mitchell
patent: 4238728 (1980-12-01), Wells, Jr. et al.
Mewett, R., "Design Considerations for a Field-Service Digital Multimeter", Control & Instrumentation, Oct. 1977, pp. 25-27.
Baker Stephen M.
Smith Jerry
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