Electricity: measuring and testing – Magnetic – Magnetometers
Patent
1993-03-08
1994-05-10
Strecker, Gerard R.
Electricity: measuring and testing
Magnetic
Magnetometers
324133, 324202, 324251, 324260, 340326, 340600, G01R 3302, G01R 3306, G01R 3500, G08B 2100
Patent
active
053111303
ABSTRACT:
A system for detecting the presence of a magnetic field emanating from a video display terminal (VDT) in which a current induced through a sensing element is first amplified by a high gain amplifier stage having a very broad low band frequency response curve then rectified by a precision rectifier to convert the AC signal induced through the sensing element to DC current. The DC current is used as one input to a comparator, the other input being set by means of a potentiometer to provide flexibility in setting a threshold input voltage differential representative of a harmful magnetic field radiation level. The output of the threshold comparator triggers a driver which is connected to a battery powered solenoid. The solenoid actuates an indicator flag in the presence of a magnetic field which exceeds the threshold magnetic radiation level. To conserve battery energy, the energized solenoid also functions as a relay to break electrical contact between itself and the batteries simultaneously with actuating the flag indicator. An alternative embodiment invention replaces the pickup coil of the preferred embodiment with a Hall effect current sensor to sense the strength of the magnetic field. In a third embodiment of the invention a radiation detector is produced having astable multi-vibrators 250 and 256 which respectively produce an audible and visual warning signal.
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Bill Richard
Rodriguez Enrique
Rad Devices, Inc.
Strecker Gerard R.
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