Electricity: measuring and testing – Conductor identification or location – Inaccessible
Patent
1982-06-16
1984-01-17
Krawczewicz, Stanley T.
Electricity: measuring and testing
Conductor identification or location
Inaccessible
324133, G01R 2702, G01R 1914
Patent
active
044266170
ABSTRACT:
An audible test device which provides a tone when a resistance being measured is less than a selected value, the selected value being variable to a few milli-ohms. A first or second source of voltage is applied to a constant current source. The constant current generated is divided between two paths, one path including test leads holding the resistance being measured therebetween, the other path through a voltage adjusting device. The output from the voltage adjusting device is applied to one input of a voltage comparator, the voltage appearing across the resistance under test being applied to the other input of the voltage comparator. The output of the comparator is applied to a voltage controlled oscillator (VCO), the output of the VCO being applied to a piezoelectric device and to a speaker operable only when the second voltage source is utilized, thereby generating an audible tone. To set the threshold below which the audible tone will be generated, test leads are placed across a known resistance value equal to the threshold desired and the voltage adjusting device is adjusted until a tone is heard. This occurs only when the output of the voltage adjusting device exceeds the voltage across the resistance under test, the output of the comparator causing the VCO to generate an output. Thereafter, when the test leads are placed across a circuit path or resistance under test having a resistance value below the set desired value, a tone will be emitted.
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I. M. Attrill, "Modulated Alarm Generator: Frequency Modulated Audio Alarm With 10 Watt Output", Radio and Electronics Constructor (Great Britain), vol. 33, No. 10, Jun. 1980, pp. 598-600.
Bissell Henry M.
General Dynamics Pomona Division
Johnson Edward B.
Krawczewicz Stanley T.
Solis Jose M.
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