Methods of and apparatus for protecting circuit elements from electrostatic discharges
First Claim
1. A method of protecting circuit elements from electrostatic discharges between an operator and ground, comprising:
- coupling a ground strap between the operator and ground;
establishing electrical contact between the operator and a non-grounded signal input terminal of a voltage comparator circuit;
while the electrical contact between the operator and the signal input terminal remains established, applying a positive supply voltage to a positive power input terminal of the voltage comparator circuit and to a positive terminal of a safety impedance coupled with its other terminal to the non-grounded signal input terminal, whereby a voltage at the input signal terminal becomes dependent on the resistive path of the ground strap between the operator and ground; and
comparing the voltage at the signal input terminal to at least one predetermined reference voltage of the voltage comparator circuit, such comparison indicating whether the ground strap coupled between the operator and ground is electrically continuous.
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Accused Products
Abstract
The continuity of a ground strap (16) is tested by pushing down on a switch activating toggle lever (37). The toggle lever is conductive, is isolated from ground and is coupled to a signal input terminal of a test circuit module (14). Thus, when the hand of the operator touches the toggle lever to activate the test circuit module (14), the resistive path through the operator and the ground strap (16) is coupled into the test circuit as the input-terminal-to-ground resistor of a voltage divider circuit. A resulting voltage at the toggle lever causes an indication by lighting either indicator (33) or indicator (34) whether the operator is properly coupled to ground.
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Citations
10 Claims
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1. A method of protecting circuit elements from electrostatic discharges between an operator and ground, comprising:
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coupling a ground strap between the operator and ground; establishing electrical contact between the operator and a non-grounded signal input terminal of a voltage comparator circuit; while the electrical contact between the operator and the signal input terminal remains established, applying a positive supply voltage to a positive power input terminal of the voltage comparator circuit and to a positive terminal of a safety impedance coupled with its other terminal to the non-grounded signal input terminal, whereby a voltage at the input signal terminal becomes dependent on the resistive path of the ground strap between the operator and ground; and comparing the voltage at the signal input terminal to at least one predetermined reference voltage of the voltage comparator circuit, such comparison indicating whether the ground strap coupled between the operator and ground is electrically continuous. - View Dependent Claims (2, 3, 4, 5)
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6. Apparatus for protecting articles from electrostatic discharges by verifying an electrical continuity of a ground strap connection between an operator and ground comprising:
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a voltage comparator circuit including at least one differential amplifier element having a first reference signal port coupled to a reference junction of a first voltage divider circuit between a positive voltage terminal and ground, and having a first test signal port coupled to a non-grounded signal input terminal; a safety impedance having a first terminal coupled to the positive voltage terminal of the voltage comparator circuit and having a second terminal coupled to the signal input terminal; means for coupling the operator to the signal input terminal and for applying a positive supply voltage with respect to ground to the positive voltage terminal of the comparator circuit within the time period during which the operator is coupled to the signal input terminal; and means for indicating that an electrical continuity between the operator and ground includes a resistance greater than a predetermined, upper limit value of resistance whenever a voltage appearing at the first test signal port exceeds a voltage at the first reference signal port of said at least one differential amplifier. - View Dependent Claims (7, 8, 9, 10)
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Specification