Electrostatic system monitor and method therefor

• US 4,649,374 A
• Filed: 01/06/1984
• Issued: 03/10/1987
• Est. Priority Date: 01/06/1984
• Status: Expired due to Term

• Current Assignee: SpectraScan, Inc. (Desco Industries Incorporated)
• Original Assignee: SpectraScan, Inc. (Desco Industries Incorporated)
• Inventors: Hoigaard, Jan C.
• Primary Examiner(s): Rowland, James L.
• Assistant Examiner(s): Myer, Daniel
• Application Number:
  US06/568,604
• Time in Patent Office: 1,159 Days
• Field of Search: 340/653, 340/652, 340/650, 340/573, 340/649, 324/457, 324/158 F, 324/72, 324/51, 128/695, 128/696, 128/908, 361/212, 361/220, 174/556
• US Class Current: 340/573.1
• CPC Class Codes: G01R 27/20 Measuring earth resistance; Measuring contact resistance, e.g. of earth connections, e.g. plates
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: G01R 31/54 Testing for continuity
• CPC Class Codes: Y10S 128/908 Patient protection from electric shock

Abstract

An electrostatic system monitor and method for monitoring the operation of static control equipment such as conductive workbench and floor mats, conductive wrist straps, and the integrity of ground connections and soldering irons and to activate indicators and alarms when the static control equipment deteriorates or malfunctions by having resistances outside of predetermined values and ranges of resistance. The electrostatic system monitor also provides for the detection of unsafe voltage potentials on soldering irons, and for a surface resistance probe for measuring the surface conductivity of conductive surfaces of the static control equipment.

Claims

1. An electrostatic system monitor for monitoring the operation of static control equipment located at a user'"'"'s workstation, said static control equipment including (a) conductive surfaces such as a conductive workbench mat and a conductive floor mat, (b) a grounded tip soldering iron, and (c) a conductive wrist strap on the wrist of a user, said conductive surfaces and said wrist strap being connected to ground connection, said monitor and soldering iron being connected to electrical AC power having an electrical ground, said electrostatic system monitor comprising:

means connected to said ground and to said electrical ground for continuously sensing the low impedance continuity between said ground and said electrical ground, said sensing means being capable of issuing a loss-of-continuity signal in the event said low impedance exceeds a predetermined resistance value,

means responsive to the manual contact with said conductive wrist strap for determining the resistance of said conductive wrist strap, said determining means being capable of producing (a) a safe resistance signal when the determined resistance is in a predetermined resistance range, (b) a loss-of-resistance signal when the determined resistance is below said predetermined resistance range, and (c) a gain-of-resistance signal when the determined resistance is above said predetermined resistance range,

a surface resistance probe for detecting the surface resistance of said conductive surfaces when said probe is in contact with said surfaces,

means connected to said surface resistance probe for selectively measuring the conductivity of said conductive surfaces, said measuring means being capable of generating (a) an adequate conductivity signal when the surface resistance is in a predetermined resistance range, (b) an unsafe resistance signal when the surface resistance is below said predetermined resistance range, and (c) an inadequate conductivity signal when the surface resistance is above said predetermined resistance range, and

means responsive to a periodic manual contact with the tip of said soldering iron for detecting induced AC voltage, said detecting means being capable of producing an unsafe voltage signal when said induced AC voltage exceeds a preset voltage.

2. The electrostatic system monitor of claim 1 further comprising:

a first visual indicator receptive of said loss-of-continuity signal from said sensing means for indicating that the impedance between said ground and said electrical ground has exceeded said predetermined resistance value, and

an audible alarm receptive of said loss-of-continuity signal from said sensing means for audibly indicating that the impedance between said ground and said electrical ground has exceeded said predetermined resistance value.

3. The electrostatic system monitor of claim 2 wherein said predetermined resistance value is substantially 100 ohms.

4. The electrostatic system monitor of claim 2 further comprising:

a second visual indicator receptive of said safe resistance and loss-of-resistance signals from said determining means for indicating that the resistance is less than or within said predetermined resistance range, and

said audible alarm being further receptive of said loss-of-resistance signal from said determining means for indicating that the resistance is less than that of said predetermined resistance range.

5. The electrostatic monitor of claim 4 wherein said predetermined resistance range is between substantially 200 Kilohms and 2.5 Megohms.

6. The electrostatic system monitor of claim 4 further comprising:

said second visual indicator being further receptive of said adequate and unsafe resistance signals from said measuring means for indicating that the surface resistance is less than or within said predetermined conductivity range, and

said audible alarm being further receptive of said unsafe resistance signal from said measuring means for indicating that the surface resistance is less than that of said predetermined resistance range.

7. The electrostatic system monitor of claim 6 wherein said predetermined adequate conductivity range is between 10 Megohms per square inch and 3000 Megohms per square inch.

8. The electrostatic system monitor of claim 2 further comprising:

a third visual indicator receptive of said unsafe voltage signal from said detecting means for indicating that said soldering iron is not safe to use, and

said audible alarm being further receptive of said unsafe voltage signal from said detecting means for indicating that said soldering iron is not safe to use.

9. The electrostatic system monitor of claim 8 wherein said preset voltage is substantially five volts RMS.

10. The electrostatic system monitor of claim 1 wherein said detecting means comprises:

a high impedance load receptive of said induced AC voltage from said soldering iron tip,

means receptive of said AC voltage across said high impedance load for rectifying said voltage, said rectifying means being further capable of doubling said AC voltage, and

means receptive of said rectified and doubled voltage from said rectifying mean for issuing said unsafe voltage signal when said rectified and doubled voltage exceeds said preset voltage.

11. The electrostatic system monitor of claim 1 wherein said surface resistance probe comprises:

a handle made from highly insulating material,

a pair of flexible and insulating bumpers connected to the underside of said handle on opposing ends thereof, and

a pair of conductive contact blocks connected on the underside of said bumpers, said contact blocks being capable of adjusting to uneven contact surfaces on said mats by means of the flexing action of said bumpers, said bumpers further holding said contact blocks a predetermined distance apart.

12. The electrostatic system monitor of claim 1 further comprising:

means operative upon the activation of said audible alarm for generating an alarm signal, and

means located remote from said generating means and receptive of said alarm signal for monitoring when said alarm signal is generated.

13. An electrostatic system monitor for monitoring the operation of static control equipment at a user'"'"'s workstation, said static control equipment including (a) conductive surfaces such as a conductive workbench mat and a conductive floor mat, (b) a grounded tip soldering iron, and (c) a conductive wrist strap on the wrist of a user, said conductive surfaces and wrist strap being connected to a ground connection, said monitor and soldering iron being connected to electrical AC power having an electrical ground, said electrostatic system monitor comprising:

means connected to said ground and to said electrical ground for continuously sensing the low impedance continuity between said ground and said electrical ground, said sensing means being capable of issuing a loss-of-continuity signal in the event said low impedance exceeds a predetermined resistance value,

a first indicator receptive of said loss-of-continuity signal from said sensing means for indicating that the impedance between said ground and said electrical ground has exceeded said predetermined resistance value,

means responsive to a manual contact with said conductive wrist strap for determining the resistance of said conductive wrist strap, said determining means being capable of producing (a) a safe resistance signal when the determined resistance is in a predetermined resistance range, (b) a loss-of-resistance signal when the determined resistance is below said predetermined resistance range, and (c) a gain-of-resistance signal when the determined resistance is above said predetermined resistance range,

a surface resistance probe for detecting the surface resistance of said conductive surfaces when said probe is in contact with said conductive surfaces,

means connected to said surface resistance probe for selectively measuring the conductivity of said conductive surfaces, said measuring means being capable of generating (a) an adequate conductivity signal when the surface resistance is in a predetermined resistance range, (b) an unsafe resistance signal when the surface resistance is below said predetermined resistance range, and (c) an inadequate conductivity signal when the surface resistance is above said predetermined resistance range,

a second indicator receptive of said safe resistance and loss-of-resistance signals from said determining means and of said adequate and unsafe resistance signals from said measuring means for becoming activated upon the receipt of any one of the aforesaid signals,

means responsive to a manual contact with the tip of said soldering iron for detecting induced AC voltage, said detecting means being capable of producing an unsafe voltage signal when said induced AC voltage exceeds a preset voltage,

a third indicator receptive of said unsafe voltage signal from said detecting means for indicating that said soldering iron is not safe to use, and

an alarm receptive of (a) said loss-of-continuity signal from said sensing means, (b) said loss-of-resistance signal from said determining means, (c) said unsafe resistance signal from said measuring means, and (d) said unsafe voltage signal from said detecting means for becoming activated upon the receipt of any one of the aforesaid signals.

14. The electrostatic system monitor of claim 13 further comprising:

means operative upon the activation of said audible alarm for generating an alarm signal, and

means located remote from said generating means and receptive of said alarm signal for monitoring when said alarm signal is generated.

15. An electrostatic system monitor for monitoring the operation of static control equipment at a user'"'"'s workstation, said static control equipment including (a) conductive surfaces such as a conductive workbench mat and a conductive floor mat, (b) a grounded tip soldering iron, and (c) a conductive wrist strap on the wrist of a user, said conductive surfaces and wrist strap being connected to a ground connection, said monitor and soldering iron being connected to electrical AC power having an electrical ground, said electrostatic system monitor comprising:

means connected to said ground and to said electrical ground for continuously sensing the low impedance continuity between said ground and said electrical ground, said sensing means being capable of issuing a loss-of-continuity signal in the event said low impedance exceeds a predetermined resistance value,

a first indicator receptive of said loss-of-continuity signal from said sensing means for indicating that the impedance between said ground and said electrical ground has exceeded said predetermined resistance value,

means responsive to a manual contact with said conductive wrist strap for determining the resistance of said conductive wrist strap, said determining means being capable of producing (a) a safe resistance signal when the determined resistance is in a predetermined resistance range, (b) a loss-of-resistance signal when the determined resistance is below said predetermined resistance range, and (c) a gain-of-resistance signal when the determined resistance is above said predetermined resistance range,

a second indicator receptive of said safe resistance and loss-of-resistance signals from said determining means for becoming activated upon the receipt of any one of the aforesaid signals,

means responsive to a manual contact with the tip of said soldering iron for detecting induced AC voltage, said detecting means being capable of producing an unsafe voltage signal when said induced AC voltage exceeds a preset voltage,

a third indicator receptive of said unsafe voltage signal from said detecting means for indicating that said soldering iron is not safe to use, and

an alarm receptive of (a) said loss-of-continuity signal from said sensing means, (b) said loss-of-resistance signal from said determining means, and (c) said unsafe voltage signal from said detecting means for becoming activated upon the receipt of any one of the aforesaid signals.

16. The electrostatic system monitor of claim 15 further comprising:

means operative upon the activation of said audible alarm for generating an alarm signal, and

means located remote from said generating means and receptive of said alarm signal for monitoring when said alarm signal is generated.

17. An electrostatic system monitor for monitoring the operation of static control equipment such as a wrist strap at a user'"'"'s workstation, said static control equipment being connected to a ground connection, said monitor being connected to electrical AC power having an electrical ground, said electrostatic system monitor comprising:

means connected to said ground and to said electrical ground for continuously sensing the low impedance continuity between said ground and said electrical ground, said sensing means being capable of issuing a loss-of-continuity signal in the event said low impedance exceeds a predetermined resistance value,

a first indicator receptive of said loss-of-continuity signal from said sensing means for indicating that the impedance between said ground and said electrical ground has exceeded said predetermined resistance value,

means responsive to a manual contact with said static control equipment for determining the resistance of said equipment, said determining means being capable of producing (a) a safe resistance signal when the determined resistance is in a predetermined resistance range, (b) a loss-of-resistance signal when the determined resistance is below said predetermined resistance range, and (c) a gain-of-resistance signal when the determined resistance is above said predetermined resistance range,

a second indicator receptive of said safe resistance and loss-of-resistance signals from said determining means for becoming activated upon the receipt of any one of the aforesaid signals, and

an alarm receptive of said loss-of-continuity signal from said sensing means and said loss-of-resistance signal from said determining means, for becoming activated upon the receipt of any one of the aforesaid signals.

18. A method for monitoring the operation of static control equipment at a user'"'"'s workstation, said static control equipment including (a) conductive surfaces such as a conductive workbench mat and a conductive floor mat, (b) a grounded tip soldering iron, and (c) a conductive wrist strap on the wrist of a user, said conductive surfaces and wrist strap being connected to a ground connection, said soldering iron being connected to electrical AC power having an electrical ground, said method comprising the steps of:

continuously sensing the low impedance continuity between said ground and said electrical ground,

issuing a loss-of-continuity signal in the event said low impedance exceeds a predetermined resistance value,

activating a first indicator in response to the issuance of a loss-of-continuity signal,

periodically determining the resistance of said conductive wrist strap,

producing (a) a safe resistance signal when the determined resistance of said wrist strap is in a predetermined resistance range, (b) a loss-of-resistance signal when the determined resistance of said wrist strap is below said predetermined resistance range, or (c) a gain-of-resistance signal when the determined resistance of said wrist strap is above said predetermined resistance range,

periodically measuring the surface conductivity of said conductive surfaces,

generating (a) an adequate conductivity signal when the surface resistance of said surfaces is in a predetermined resistance range, (b) an unsafe resistance signal when the surface resistance of said surfaces is below said predetermined resistance range, or (c) an inadequate conductivity signal when the measured surface resistance of said surfaces is above said predetermined resistance range,

activating a second indicator in response to the production of said safe resistance and loss-of-resistance signals and in response to the generation of said adequate conductivity and unsafe resistance signals,

periodically detecting induced AC voltage on the tip of said soldering iron,

producing an unsafe voltage signal when said detected AC voltage exceeds a preset voltage,

activating a third indicator in response to the production of said unsafe voltage signal, and

activating an alarm in response to (a) the issuance of said loss-of-continuity signal, (b) the production of said loss-of-resistance signal, (c) the generation of said unsafe resistance signal, or (d) the production of said unsafe voltage signal.

19. The method of claim 18 further comprising the step of issuing an alarm signal to a central monitor in response to the activating of said alarm.

20. A method for monitoring the operation of static control equipment at a user'"'"'s workstation, said static control equipment including (a) conductive surfaces such as a conductive workbench mat and a conductive floor mat, (b) a grounded tip soldering iron, and (c) a conductive wrist strap on the wrist of a user, said conductive surfaces and wrist strap being connected to a ground connection, said soldering iron being connected to electrical AC power having an electrical ground, said method comprising the steps of:

continuously sensing the low impedance continuity between said ground and said electrical ground,

issuing a loss-of-continuity signal in the event said low impedance exceeds a predetermined resistance value,

periodically determining the resistance of said conductive wrist strap,

producing (a) a safe resistance signal when the determined resistance of said wrist strap is in a predetermined resistance range, (b) a loss-of-resistance signal when the determined resistance of said wrist strap is below said predetermined resistance range, or (c) a gain-of-resistance signal when the determined resistance of said wrist strap is above said predetermined resistance range,

periodically measuring the surface conductivity of said conductive surfaces,

generating (a) an adequate conductivity signal when the surface resistance of said surfaces is in a predetermined resistance range, (b) an unsafe resistance signal when the surface resistance of said surfaces is below said predetermined resistance range, or (c) an inadequate conductivity signal when the measured surface resistance of said surfaces is above said predetermined conductivity range,

periodically detecting induced AC voltage on the tip of said soldering iron, and

producing an unsafe voltage signal when said detected AC voltage exceeds a preset voltage.

21. A method for monitoring the operation of static control equipment at a user'"'"'s workstation, said static control equipment being connected to a ground connection, said method comprising the steps of:

continuously sensing the low impedance continuity between said earth ground and the electrical ground found at the user'"'"'s workstation,

issuing a loss-of-continuity signal in the event said low impedance exceeds a predetermined resistance value,

periodically determining the resistance of said static control equipment, and

producing (a) a safe resistance signal when the determined resistance of said equipment is in a predetermined resistance range, (b) a loss-of-resistance signal when the determined resistance of said equipment is below said predetermined resistance range, or (c) a gain-of-resistance signal when the determined resistance of said equipment is above said predetermined resistance range.

22. The method of claim 21 further comprising the steps of:

measuring the surface conductivity of said static control equipment, and

generating (a) an adequate conductivity signal when the surface resistance of said equipment is in a predetermined resistance range, (b) an unsafe resistance signal when the surface resistance of said equipment is below said predetermined resistance range, or (c) an inadequate conductivity signal when the surface resistance of said equipment is above said predetermined resistance range.

23. A method for monitoring the operation of the grounded tip soldering iron at a user'"'"'s workstation, said soldering iron being connected to electrical AC power having an electrical ground, said method comprising the steps of:

detecting induced AC voltage on the tip of said soldering iron by periodically touching the tip of the soldering iron to a high impedance load,

producing an unsafe voltage signal when said detected AC voltage across the high impedance load exceeds a preset voltage, and

activating an indicator in response to the production of said unsafe voltage signal.

24. The method of claim 23 further comprising the steps of:

continuously sensing the low impedance continuity between said ground and said electrical ground, and

issuing a loss-of-continuity signal in the event said low impedance exceeds a predetermined resistance value.