Q: How can I ensure that a cart is grounded? I have found that when a cart is moving, it is grounded with a drag chain. But when a cart is stationary, the chain link contacting the floor does not always make good contact with the link hanging from the cart.

A: Begin by providing a means of contact between the cart and the floor. Chains and straps may be used to accomplish this, but, as you have experienced, these items may have only intermittent contact with the floor and may not be very effective from a static control standpoint. Conductive or dissipative wheels or casters are generally a more effective alternative and should be used on all wheels to improve consistency of electrical contact with the floor. Also remember: the wider the caster or wheel, the better the electrical contact with the floor.

Next, be sure the cart has electrical continuity between the shelves and the frame of the cart, and between the frame and the wheels. Shelves often rest on insulating supports, and the frames may be insulated from the wheels. If you can't replace insulating fittings with conductive ones, you may need to provide an alternative electrical connection from one part to another.

The third step is making sure that the cart has a provision for being connected to ground when it is stationary in the work area. This will help solve the problem of poor electrical contact with the floor when the cart is not moving.

Finally, remember that even wheels, casters, ground straps, and ground chains can become dirty, creating an insulating layer between them and the floor. Clean them regularly to maintain the proper electrical contact.

Q: Where can I find ESD sensitivity information for specific microhybrid electronic components (i.e., ICs, resistors, capacitors, CMOS ICs, etc.)?

A: The first source is the manufacturer or the supplier of the particular component. An additional source is the IIT Research Institute's Reliability Analysis Center (RAC) in Rome, NY. The organization issues VZAP-95, Electrostatic Discharge Susceptibility Data, which contains ESD susceptibility data for 22,000 devices, including microcircuits. To obtain additional information, contact the RAC at 201 Mill St., Rome, NY 13440-6916; tel: 888/722-8737; fax: 315/337-9932; Internet: http://www.rac.iitri.org.

To submit your questions to the ESD Help Desk or to browse the archives of past questions and answers, go on-line at http://www.ce-mag/esdhelp.html. Information on the ESD Association may be found at http://www.eosesd.org.