Static monitoring system
First Claim
1. In a static monitoring system for use with a work station for measuring change in electrostatic potential adjacent the work station, the combination of:
- an antenna;
means for positioning said antenna adjacent the work station for producing a change in current in said antenna as a function of movement of a statically charged object in the electrostatic field adjacent the work station;
a first amplifier having at least one input and an output, said first amplifier having a non-linear feedback circuit from said output to said one input thereof;
means for connecting said antenna to said one input of said first amplifier;
a line frequency filter having said output of said first amplifier as an input;
a signal level detector having the output of said filter as an input; and
an alarm unit having the output of said detector as an input;
said first amplifier being a non-linear operational amplifier whereby said alarm unit is actuated when the change in the current in said antenna exceeds a predetermined value.
1 Assignment
0 Petitions
Accused Products
Abstract
A static monitoring system for use with an electronic manufacturing work area, typically a conventional work bench having an electrical conducting strap for connecting the operator'"'"'s wrist to earth ground, and including a circuit for indicating when there is an earth ground connection and circuitry for indicating when an electrostatically charged object, such as another human, approaches the work station. An antenna is positioned at the work station spaced from the working surface and from the operator, with the antenna connected as an input to an amplifier circuit which measures the change in electrostatic field strength and hence the approach of a charged object, with an indicator providing a visual or audible alarm or both. An oscillator provides an ac signal to each input of a differential amplifier, with one input connected to circuit ground through a capacitor and the other input connected to a wrist strap or the like on the operator. Phase difference at the amplifier inputs is detected as a measure of the capacitance to ground at the wrist strap thereby indicating appropriate use of the wrist strap.
33 Citations
9 Claims
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1. In a static monitoring system for use with a work station for measuring change in electrostatic potential adjacent the work station, the combination of:
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an antenna; means for positioning said antenna adjacent the work station for producing a change in current in said antenna as a function of movement of a statically charged object in the electrostatic field adjacent the work station; a first amplifier having at least one input and an output, said first amplifier having a non-linear feedback circuit from said output to said one input thereof; means for connecting said antenna to said one input of said first amplifier; a line frequency filter having said output of said first amplifier as an input; a signal level detector having the output of said filter as an input; and an alarm unit having the output of said detector as an input; said first amplifier being a non-linear operational amplifier whereby said alarm unit is actuated when the change in the current in said antenna exceeds a predetermined value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification