Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Frequency of cyclic current or voltage
Patent
1980-03-10
1983-07-19
Strecker, Gerard R.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Frequency of cyclic current or voltage
324 54, G01R 3102, G01R 3112
Patent
active
043946151
ABSTRACT:
Portable apparatus for testing the quality of a ground connection between the ground prong of a tool plug and the tool housing, and for testing the quality of insulation between the tool plug power prongs and the tool housing. The apparatus comprises an enclosure having a plug at one end adapted to be received into a conventional utility wall outlet and a receptacle at the other end for receiving a tool power plug. A pair of electrical contact plates are provided as two adjacent outside walls of the enclosure. Threshold detection circuitry carried internally of the housing is connected to the power and ground receptacles of the apparatus plug and to the contact plates. A first portion of the circuitry is effective for measuring the resistance between the ground prong of a tool plug inserted into the apparatus receptacle and a tool housing in physical contact with one of the contact plates. A second portion of the circuitry is effective for simultaneously measuring the resistance between the tool plug power prongs and the tool housing. LED's are connected to the measuring circuitry and observable by a user for indicating safe or unsafe ground or insulation quality.
REFERENCES:
patent: 3277364 (1966-10-01), Abrahamson
patent: 3643157 (1972-02-01), Ettelman
patent: 3798540 (1974-03-01), Darden et al.
patent: 3837844 (1974-09-01), Prugh
Snow Walter E.
Strecker Gerard R.
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