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Teledyne API – Model T300/T300M CO Analyzer A Primer on Electro-Static Discharge
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Simply touching a grounded piece of metal is insufficient. While this may
temporarily bleed off static charges present at the time, once you stop touching the
grounded metal new static charges will immediately begin to re-build. In some
conditions, a charge large enough to damage a component can rebuild in just a few
seconds.
Always store sensitive components and assemblies in anti-ESD storage bags
or bins: Even when you are not working on them, store all devices and assemblies
in a closed anti-Static bag or bin. This will prevent induced charges from building up
on the device or assembly and nearby static fields from discharging through it.
Use metallic anti-ESD bags for storing and shipping ESD sensitive
components and assemblies rather than pink-poly bags. The famous, pink-poly
bags are made of a plastic that is impregnated with a liquid (similar to liquid laundry
detergent) which very slowly sweats onto the surface of the plastic creating a slightly
conductive layer over the surface of the bag.
While this layer may equalizes any charges that occur across the whole bag, it does
not prevent the build up of static charges. If laying on a conductive, grounded
surface, these bags will allow charges to bleed away but the very charges that build
up on the surface of the bag itself can be transferred through the bag by induction
onto the circuits of your ESD sensitive device. Also, the liquid impregnating the
plastic is eventually used up after which the bag is as useless for preventing
damage from ESD as any ordinary plastic bag.
Anti-Static bags made of plastic impregnated with metal (usually silvery in color)
provide all of the charge equalizing abilities of the pink-poly bags but also, when
properly sealed, create a Faraday cage that completely isolates the contents from
discharges and the inductive transfer of static charges.
Storage bins made of plastic impregnated with carbon (usually black in color) are
also excellent at dissipating static charges and isolating their contents from field
effects and discharges.
Never use ordinary plastic adhesive tape near an ESD sensitive device or to
close an anti-ESD bag. The act of pulling a piece of standard plastic adhesive
tape, such as Scotch
®
tape, from its roll will generate a static charge of several
thousand or even tens of thousands of volts on the tape itself and an associated
field effect that can discharge through or be induced upon items up to a foot away.
14.4.2. BASIC ANTI-ESD PROCEDURES FOR ANALYZER REPAIR AND
MAINTENANCE
14.4.2.1. WORKING AT THE INSTRUMENT RACK
When working on the analyzer while it is in the instrument rack and plugged into a
properly grounded power supply:
1. Attach you anti-ESD wrist strap to ground before doing anything else.
Use a wrist strap terminated with an alligator clip and attach it to a bare metal
portion of the instrument chassis.
This will safely connect you to the same ground level to which the instrument
and all of its components are connected.
2. Pause for a second or two to allow any static charges to bleed away.
3. Open the casing of the analyzer and begin work. Up to this point, the closed metal
casing of your analyzer has isolated the components and assemblies inside from
any conducted or induced static charges.
06864B DCN6314