ESD monitoring circuit and device
First Claim
1. An electrometer comprising:
- a first input channel termed a proximity detect channel,a second input channel termed a probe channel,a means to display a voltage detected by said electrometer;
whereininputs to said two input channels are attenuated respectively by a first active voltage divider and a second active voltage divider, said active voltage dividers are constructed to give said electrometer an extremely high input impedance on the order of 100 gigohms, thereby allowing said electrometer to measure an ESC without causing a rapid discharge.
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Accused Products
Abstract
An electrometer that is able to measure the potential difference of an electrostatically charged body without causing a rapid discharge of the subject charge. The electrometer has an input impedance that is in excess of 100 gigohms. The input impedance is created by an active voltage divider. The active voltage divider is a unique circuit which instead of the typical voltage divider that utilizes a passive resistive divider and an op amp in a voltage follower configuration, uses an amplifier configuration that attenuates its input signal. One result of this configuration is that the input line can then be guarded. This allows the device to be supplied with probes that are not subject to typical elements of degradation of the input signal with distance from the circuit, e.g. parasitic capacitance and bandwidth limitations. The device operates with two channels: a first channel recognizes the presence of a charged body in the proximity of the device, while the second channel measures the magnitude of the potential difference on a charged body examined by a probe. The device includes alarms that are activated when charge levels exceed a chosen level. A display tower allows a user to visually demonstrate to trainees the magnitude of ESC events.
19 Citations
27 Claims
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1. An electrometer comprising:
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a first input channel termed a proximity detect channel, a second input channel termed a probe channel, a means to display a voltage detected by said electrometer;
whereininputs to said two input channels are attenuated respectively by a first active voltage divider and a second active voltage divider, said active voltage dividers are constructed to give said electrometer an extremely high input impedance on the order of 100 gigohms, thereby allowing said electrometer to measure an ESC without causing a rapid discharge. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An electrometer comprising:
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a first input channel termed a proximity detect channel, a second input channel termed a probe channel, a means to display a voltage detected by said electrometer;
whereininputs to said two input channels are attenuated respectively by a first active voltage divider and a second active voltage divider, said active voltage dividers are constructed to give said electrometer an extremely high input impedance on the order of 100 gigohms, thereby allowing said electrometer to measure an ESC without causing a rapid discharge, the active voltage dividers utilizing an op amp in a configuration such that input voltage is attenuated rather than amplified, said configuration including a first resistor, a second resistor, and said op amp;
whereinsaid first resistor has a first electrical contact with an inverting input terminal of said op amp, said first resistor has a second electrical contact with an output terminal of said op amp, said second resistor is in the input path to said inverting input terminal of said op amp, such that the attenuation achieved by said active voltage dividers is equal to a ratio of said first resistor to said second resistor. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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Specification