Wrist strap test mode circuitry

• US 5,872,455 A
• Filed: 05/16/1997
• Issued: 02/16/1999
• Est. Priority Date: 05/16/1997
• Status: Expired due to Fees

• Current Assignee: Northrop Grumman Corporation
• Original Assignee: Northrop Grumman Corporation
• Inventors: Trainor, Michael J., Guthrie, Warren E., Pohribnij, Walter Jerry
• Primary Examiner(s): Do, Diep N.
• Application Number:
  US08/857,606
• Time in Patent Office: 641 Days
• Field of Search: 324/509, 324/452, 324/454, 324/456, 324/457, 324/510, 340/649, 340/650, 361/212, 361/220
• US Class Current: 324/509
• CPC Class Codes: G01R 31/14 Circuits therefor , e.g. for generating test voltages, sensing circuits G01R31/1209 - G01R31/1227 take precedence; for testing switches G01R31/327

Abstract

Improved electronic circuitry incorporated into a tag attached to a user worn wrist strap of a static electrical discharge dissipation system. The electronic circuitry monitors the electrical connection of the wrist strap from the user to ground and tests the functionality of the tag. The electronic circuitry comprises an oscillator, a signal transmitter, a discharge resistor and a discharge resistor check circuit for monitoring the accuracy of the discharge resistor. The electronic circuitry also comprises a skin resistance check circuit for monitoring the electrical connection of the wrist strap to the user, and a ground fault detect circuit for monitoring the electrical connection of the wrist strap to ground. The electronic circuitry further comprises a testing circuit for checking the frequency of the oscillator, monitoring the spectrum of a signal transmitted by the signal transmitter, checking the functionality of the ground fault detect circuit, checking low and high limits of the discharge resistor, and checking the functionality of the skin resistance check circuit.

Claims

1. In a static electrical discharge dissipation system having a dissipation device which is worn by a user and a conductive line for electrically connecting the dissipation device to ground, the improvement comprising a communication device including electronic circuitry which electrically communicates with the dissipation device and the conductive line, and is operable to monitor the electrical connection of the dissipation device to ground and test the functionality of the communication device, the electronic circuitry of the communication device including:

an oscillator for generating electronic circuitry timing signals;

a discharge resistor for preventing a direct short to ground when the user contacts an active electrical conductor;

a signal transmitter for transmitting signals representative of the functionality of the electronic circuitry, the dissipation device, and the conductive line;

a discharge resistor check circuit for monitoring the accuracy of the discharge resistor;

a skin resistance check circuit for monitoring the electrical connection of the dissipation device to the user;

a ground fault detect circuit for monitoring the electrical connection of the dissipation device to ground; and

a testing circuit for checking the frequency of the oscillator, monitoring the spectrum of the signal transmitted by the signal transmitter, checking the functionality of the ground fault detect circuit, checking a low limit of the discharge resistor, checking a high limit of the discharge resistor, and checking the functionality of the skin resistance check circuit.

2. The electronic circuitry of claim 1 wherein said discharge resistor check circuit is configured to perform a high limit check of the discharge resistor and a low limit of the discharge resistor.

3. The electronic circuitry of claim 2 wherein said testing circuit is configured to conduct a series of tests, including:

a first test where the oscillator is caused to generate a continuous sequence for allowing the frequency of the oscillator to be checked and properly tuned;

a second test wherein the signal transmitter is caused to transmit a signal to allow the spectrum of the signal to be monitored;

a third test wherein the ground fault detect circuit is enabled to monitor the response of the tag to ground and no ground;

a fourth test wherein the discharge resistor check circuit is enabled to allow the low limit of the discharge resistor to be checked;

a fifth test wherein the discharge resistor check circuit is enabled to allow the high limit of the discharge resistor to be checked; and

a sixth test wherein the skin resistance check circuit is enabled to allow a maximum skin resistance detect to be tested.

4. The electronic circuitry of claim 3 wherein the continuous sequence comprises a 2.414 GHz +/-20 kHz signal at 0 dBm having a 1s modulation.

5. The electronic circuitry of claim 3 wherein the signal transmitted by the signal transmitter is a direct sequence spread spectrum signal having a main lobe of a width of approximately 1 MHz.

6. The electronic circuitry of claim 3 wherein the low limit of the discharge resistor is approximately 700 kohm.

7. The electronic circuitry of claim 3 wherein the high limit of the discharge resistor is approximately 1.3 Megohm.

8. The electronic circuitry of claim 3 wherein the maximum skin resistance detect is approximately 8 Megohm.

9. The electronic circuitry of claim 1 wherein the dissipation device comprises a static wrist strap having the communication device attached thereto.

10. The electronic circuitry of claim 1 wherein the discharge resistor check circuit, the skin resistance check circuit, and the ground fault detect circuit are each integrated into a sensor circuit of the electronic circuitry.

11. The electronic circuitry of claim 10 wherein the sensor circuit is incorporated into a microprocessor of the electronic circuitry.

12. The electronic circuitry of claim 11 wherein the testing circuit is incorporated into the microprocessor.

13. The electronic circuitry of claim 1 wherein the communication device into which the electronic circuitry is incorporated comprises a transmitter.

14. The electronic circuitry of claim 1 wherein the communication device into which the electronic circuitry is incorporated comprises a transceiver.

15. In a static electrical discharge dissipation system having a dissipation device which is worn by a user and a conductive line for electrically connecting the dissipation device to ground, a method for monitoring the electrical connection of the dissipation device to ground and testing the functionality of the dissipation device, comprising the steps of:

(a) providing a communication device including electronic circuitry which electrically communicates with the dissipation device and the conductive line, and has a discharge resistor for preventing a direct short to ground when the user contacts an active electrical conductor, a signal transmitter for transmitting signals representative of the functionality of the electronic circuitry, the dissipation device, and the conductive line, and an oscillator for generating electronic circuitry timing signals;

(b) monitoring the accuracy of the discharge resistor via a discharge resistor check circuit of the electronic circuitry;

(c) monitoring the electrical connection of the dissipation device to the user via a skin resistance check circuit of the electronic circuitry;

(d) monitoring the electrical connection of the dissipation device to ground via a ground fault detect circuit of the electronic circuitry;

(e) checking the frequency of the oscillator via a testing circuit of the electronic circuitry;

(f) monitoring the spectrum of the signal transmitted by the signal transmitter via the testing circuit;

(g) checking the functionality of the ground fault detect circuit via the testing circuit;

(h) checking a low limit of the discharge resistor via the testing circuit;

(i) checking a high limit of the discharge resistor via the testing circuit; and

(j) checking the functionality of the skin resistance check circuit via the testing circuit.

16. The method of claim 15 wherein step (b) comprises performing a high limit check of the discharge resistor and a low limit check of the discharge resistor.

17. The method of claim 15 wherein step (e) comprises causing the oscillator to generate a continuous sequence for allowing the frequency of the oscillator to be checked and properly tuned.

18. The method of claim 17 wherein step (e) comprises causing the oscillator to generate a 2.414 GHz +/-20 kHz signal at 0 dBm having a 1s modulation.

19. The method of claim 15 wherein step (f) comprises causing the signal transmitter to transmit a signal to allow the spectrum of the signal to be monitored.

20. The method of claim 19 wherein step (f) comprises causing the signal transmitter to transmit a direct sequence spread spectrum signal having a main lobe of a width of approximately 1 MHz.

21. The method of claim 15 wherein step (g) comprises enabling the ground fault detect circuit to monitor the response of the communication device to ground and no ground.

22. The method of claim 16 wherein step (h) comprises enabling the discharge resistor check circuit to allow the low limit of the discharge resistor to be checked.

23. The method of claim 22 wherein step (a) comprises providing the discharge resistor with the low limit of approximately 700 kohm.

24. The method of claim 16 wherein step (i) comprises enabling the discharge resistor check circuit to allow the high limit of the discharge resistor to be checked.

25. The method of claim 24 wherein step (a) comprises providing the discharge resistor with the high limit of approximately 1.3 Megohm.

26. The method of claim 15 wherein step (j) comprises enabling the skin resistance check circuit to allow a maximum skin resistance detect to be tested.

27. The method of claim 26 wherein step (j) comprises providing the maximum skin resistance detect as approximately 8 Megohm.