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Questions From Readers
This question was submitted by Robert Meston, Senior QA Engineer (Space Group), BAE Systems:
"PC monitors emit very litle ESD fields at the screen, but the cathode gun and the power supply generate a field of 1Kv to 15 Kv. The British Standard 10015 states 'Electrostatic fields that are generated internal or external to the EPA shall be such that the maximum potential at any unprotected point inside the EPA shall be 100V'. On the shop floor operators use a PC to control their build assembly etc. The PC is within the EPA. There are cleaners available for the screen, but that is not the source of the static. We have reviewed flat screen monitors, and they tend to pass except two vent holes in the top of the monitors where hot air is exiting and charging up the air which fails the 100v. Flat screens would appear to be the answer as the static field has been reduced dramatically, but flat screen monitors are still rather expensive and they marginally fail. We have tried putting earthed shields around the monitors, but they take up too much space on the worstation and look cumbersome. Does anyone have any suggestions? I personally think the requirement is useless. If you check the static field in the morning at start of shift, and it is less that 100v; it is deemed ok. If someone brushes against the monitor or cleans the case etc it fails the static field test."
E-mail your answers or suggestions to qestionscrt@esdjournal.com |