The present invention relates to industrial and other operations that are sensitive to the build-up and discharge of electro-static energy, and, more particularly, to electronic industries, paint shops and grain silos where electrostatic discharge may cause component damage, equipment damage, injury or death.
Electrostatic energy build-up and discharge is a relatively well-understood operational problem. Under specific circumstances, materials and/or the operator and/or their clothing can become charged with significant electrostatic potential.
The uncontrolled discharge of this potential can destroy electronic components and can cause dangerous dust or particle explosions. The prevention of static build-up on operators in certain industries has significant economic and safety implications.
In electronic process and manufacturing industries, electrostatic discharge (ESD) is a serious issue for solid-state electronics, such as integrated circuits. Integrated circuits are made from semiconductor materials such as silicon and insulating materials such as silicon dioxide. Either of these materials can suffer permanent damage when subjected to high voltages as a result of ESD through the device.
For these industries, there are two main methods of protection. Firstly, the device under construction may be designed in ways that mitigate the effect of an ESD event by routing the energy away from sensitive areas. Many IC and board designs use this approach. Secondly, standard manufacturing procedures require that all assembly personnel and equipment be adequately grounded. Adequate grounding of the operator and equipment prevents harmful voltages from accumulating and the handling of components and devices is protected from ESD events.
In recent years, there have been significant advances in the use of local and personal area networks and in the use of RF identification tags (RFID). These technologies have, so far, not been applied effectively to the ESD industry. Whereas there are wireless solutions in the market place, they are power hungry requiring sizeable batteries to make them work and are thus not wrist strap implementations.
For a static wrist/heel strap, the integrity of the ground connection is tested once per day at a test stand or each time the technician returns to the manufacturing area. This test is from the ground through the body through the wrist/heel strap and back to the ground.
There are existing solutions that provide ground protection and monitoring. Existing solutions may be loosly divided into passive and active categories. Passive—without continuous monitoring, active—with continuous monitoring.
Existing passive solutions, whilst low cost, have the significant and very specific limitation of only assuring adequate grounding at the time of the test. They are not able to positively assure grounding at the specific time of contact with the work. Manufacturers are unable to ensure ESD protection during manufacture of a clients product and rely on safe working practices to assure that the process was likely to be protected.
Existing active solutions involve the use of complex wiring infrastructure to both ground the user and measure the ground potential separately. In particular, these devices are typically exclusively located on each bench that the operator may use. They involve the maintenance of an expensive grounded work-station that is difficult to move and difficult to monitor remotely.
Further, for both types of system, it is often difficult if not impossible for a customer to resolve a damaged board to a possible ESD event after the fact. With no record of any ground faults and no record of specifically when a board was worked on or by whom, the customer relies heavily on the adequate maintenance of operational standard practices with little to no visibility of the process.
It is therefore an object of the invention to provide a means of electronic monitoring an operators ground connection and provide continuous visual and/or auditory feedback to the operator of the ground connection state.
It is another object of the invention to provide the means by which the operator and ground connection state can be correlated against process parameters including but not limited to work-flow, components, followers and work place location using RFID and other pertinent technology.
It is another object of the invention to provide the means by which the various related operational parameters described above may be communicated wirelessly to a remote data logging and presentation device.
In accordance with the present invention, there is provided a device that can electronically track operator ground connectivity to; a) provide continuous visual and/or auditory indication of connection state, b) optionally provide that the ground connectivity state may be monitored and displayed remotely using RF communications, and c) optionally provide that the operators device can track RFID ‘follower’ tags specifically placed to facilitate work-flow data ecording and the correlation of the operators activities with specific work-flow process.
A complete understanding of the present invention may be obtained by reference to the accompanying drawings, when considered in conjunction with the subsequent, detailed description, in which:
For purposes of clarity and brevity, like elements and components will bear the same designations and numbering throughout the Figures.
One possible embodiment of the invention is shown in
By using an wearable active wrist monitor 16, the operator is freed from expensive equipment installation and may work wherever there is an adequate ground connection as shown in
When the Ground connection lead 34 is connected to the Ground lead connection post 38, the ground connection causes discrete and quantifiable changes in current at R2. The system behaves as a ground loop antenna with increased gain with improvement in ground connectivity.
DSP algorithms running in the MCU 24 are used to do envelope detection of and correlation of the current flowing flowing through the Source current sensor 30 and the Loop current sensor 32 (R1 & R2). The MCU 24 is also used to measure the capacitance from A to digital ground. A combination of the change in local impedance and the integrated delta current flow between R1 and R2 can then be reduced to an ‘adequate ground connectivity’ true/false logic state. This logic state is used to drive suitable Audio/visual indicators 26 to the operator. Audio/visual feedback is via LED 44 or small pizzo Speaker 46 (
In addition to monitoring connectivity state, it is also possible to monitor analog ground condition parameters and this data along with connectivity state may be transmitted to the base station and logged for calibration, correlation and audit purposes.
Two conductive capacitive touch pads in skin contact with the operator are used as a Capacitive touch sensor 28 to indicate that the device is being worn by the operator. One of these plates also provides ground continuity between the operator and earth.
Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the example chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of this invention.
Having thus described the invention, what is desired to be protected by Letters Patent is presented in the subsequently appended claims.
The present application is a continuation-in-part application of U.S. provisional patent application, Ser. No. 61/315,306, filed Mar. 18, 2010, for SINGLE WIRE, WEARABLE, ELECTRONIC GROUND RESISTANCE DETECTOR FOR ESD WORKPLACE PROTECTION, by Guy T R Mcllroy, included by reference herein and for which benefit of the priority date is hereby claimed.
Number | Date | Country | |
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Parent | 61315306 | Mar 2010 | US |
Child | 13048354 | US |