Method of monitoring ESC levels and protective devices utilizing the method

• US 6,762,917 B1
• Filed: 06/12/2001
• Issued: 07/13/2004
• Est. Priority Date: 06/12/2001
• Status: Expired due to Fees

• Current Assignee: Novx Corp. (MKS Instruments Incorporated)
• Original Assignee: Novx Corp. (MKS Instruments Incorporated)
• Inventors: Heymann, Steven B., Verbiest, Noel, Nelsen, Lyle
• Primary Examiner(s): Sircus, Brian
• Assistant Examiner(s): Nguyen, Danny
• Application Number:
  US09/880,202
• Time in Patent Office: 1,127 Days
• Field of Search: 361/42, 361/43, 361/44, 361/46, 361/47, 361/48, 361/49, 361/50, 361/56, 361/58, 361/111, 361/115, 361/45
• US Class Current: 361/42
• CPC Class Codes: A61B 2090/065 for measuring contact or contact pressure
• CPC Class Codes: A61B 2562/0215 Silver or silver chloride containing
• CPC Class Codes: A61B 5/276 Protection against electrode failure
• CPC Class Codes: A61B 5/301 providing electrical separation, e.g. by using isolating transformers or optocouplers
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure
• CPC Class Codes: H02H 3/04 with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned watching of pilot wires H02H1/0084; protection of protective arrangements H02H7/008; indication of the state of electronic switches H03K17/18
• CPC Class Codes: H02H 3/14 responsive to occurrence of voltage on parts normally at earth potential monitoring earth connection H02H5/105
• CPC Class Codes: H02H 3/16 responsive to fault current to earth, frame or mass with balanced or differential arrangement H02H3/26 ; monitoring earth connection H02H5/105
• CPC Class Codes: H02H 5/105 responsive to deterioration or interruption of earth connection for preventing switching-on H02H11/001

Abstract

A method of controlling and monitoring voltage potential on a human body that includes the following steps: a) Connecting the human body to a “Quasi Virtual Ground”; b) Providing contact with the human skin via one or more silver/silver chloride electrodes; c) Continuously monitoring the triboelectric current i(t) flowing into the “Quasi Virtual Ground” terminal; d) Determining whether or not a person is properly wearing his/her body electrode; e) Including circuitry that immediately interrupts the path-to-ground when a dangerously large current is detected; f) Including circuitry that immediately interrupts the path-to-ground when the power supply to the workstation monitor is interrupted, either intentionally or accidentally.

Claims

1. A circuit to control and monitor voltage potential on a human body comprising:

an electrode in contact with skin of an operator, a ground fault sensing/relay/current limit stage, and a current-to-voltage converter in a path-to-ground,

a filter,

an absolute value amplifier,

display means,

a window detector,

a ground fault bistable multivibrator,

an astable multivibrator,

an activity detector means, and

an alarm means;

wherein

triboelectric current bursts detected by said electrode enter said ground fault sensing/relay/current limit stage, a signal from said ground fault sensing/relay/current limit stage being processed through said current-to-voltage converter, said filter, and said absolute value amplifier, said absolute value amplifier converting bipolar signals into positive unipolar signals, said unipolar signals driving said display means; and

wherein

a first signal is picked off from said display means to drive said activity detector means, and concurrently, a second signal is picked off from said ground fault sensing/relay/current limit stage, said second signal being processed through said window detector and through said ground fault bistable multivibrator, outputs of said activity detector means and said ground fault bistable multivibrator drive multivibrators which in turn drive said alarm means;

such that

said alarm means is activated when said circuit does not detect said triboelectric current bursts and when inadvertent contact with a power source occurs.

2. The circuit as claimed in claim 1 wherein:

an output signal of said ground fault bistable multivibrator causes a relay to open if the operator accidentally contacts a live power wire.

3. The circuit as claimed in claim 1 wherein:

an output signal of said ground fault bistable multivibrator ensures blanking of said display means unless said ground fault bistable multivibrator has been manually reset.

4. The circuit as claimed in claim 1 wherein:

a power-on fail safe means insures that said ground fault bistable multivibrator is set to a proper logical state after any interruption in power supply.

5. The circuit as claimed in claim 1 wherein:

functions of said absolute value amplifier, said ground fault bistable multivibrator, said astable multivibrator, and said activity detector means are executed by a microprocessor.

6. The circuit as claimed in claim 1 wherein:

said circuit comprises two electrodes in contact with the skin of the operator, said two electrodes being electrically isolated, and each of said two electrodes being an element of an independent path-to-ground;

wherein

said alarm means is activated if a difference between a current flowing through a first one of said paths-to-ground and a current flowing through a second one of said paths-to-ground is greater than a predetermined level, said difference indicating a compromise in at least one of said paths-to-ground.

7. The circuit as claimed in claim 1 wherein:

said circuit comprises two electrodes in contact with the skin of the operator, said two electrodes being electrically isolated, and each of said two electrodes being an element of an independent path-to-ground;

wherein

said alarm means is activated if a voltage potential detected in either of said paths-to-ground is greater than a predetermined level, said voltage potential indicating a compromise in at least one of said paths-to-ground.