Teledyne GFC-7000T - Trace CO2 Analyzer - manual - Manual (Page 275)

ESD Model GFC7000TA Carbon Dioxide Analyzer
Teledyne Analytical Instruments 257
 Whenever a sensitive device is moved into the field of an existing electro-static field, a charge
may be induced on the device in effect discharging the field onto the device. If the device is then
momentarily grounded while within the electrostatic field or removed from the region of the
electrostatic field and grounded somewhere else, a second discharge will occur as the charge is
transferred from the device to ground.
11.3. Common Myths About ESD Damage
 I didn’t feel a shock so there was no electro-static discharge: The human nervous system
isn’t able to feel a static discharge of less than 3500 volts. Most devices are damaged by
discharge levels much lower than that.
 I didn’t touch it so there was no electro-static discharge: Electro-static charges are fields
whose lines of force can extend several inches or sometimes even feet away from the surface
bearing the charge.
 It still works so there was no damage: Sometimes the damaged caused by electro-static
discharge can completely sever a circuit trace causing the device to fail immediately. More likely,
the trace will be only partially occluded by the damage causing degraded performance of the
device or worse, weakening the trace. This weakened circuit may seem to function fine for a
short time, but even the very low voltage and current levels of the device’s normal operating
levels will eat away at the defect over time causing the device to fail well before its designed
lifetime is reached.
These latent failures are often the most costly since the failure of the equipment in which the
damaged device is installed causes down time, lost data, lost productivity, as well as possible
failure and damage to other pieces of equipment or property.
 Static Charges can’t build up on a conductive surface: There are two errors in this
statement.
Conductive devices can build static charges if they are not grounded. The charge will be
equalized across the entire device, but without access to earth ground, they are still trapped and
can still build to high enough levels to cause damage when they are discharged.
A charge can be induced onto the conductive surface and/or discharge triggered in the presence
of a charged field such as a large static charge clinging to the surface of a nylon jacket of
someone walking up to a workbench.
 As long as my analyzer is properly installed, it is safe from damage caused by static
discharges : It is true that when properly installed the chassis ground of your analyzer is tied to
earth ground and its electronic components are prevented from building static electric charges
themselves. This does not prevent discharges from static fields built up on other things, like you
and your clothing, from discharging through the instrument and damaging it.
11.4. Basic Principles of Static Control
It is impossible to stop the creation of instantaneous static electric charges. It is not, however difficult to
prevent those charges from building to dangerous levels or prevent damage due to electro-static
discharge from occurring.
11.4.1. General Rules
Only handle or work on all electronic assemblies at a properly set up ESD station. Setting up an ESD
safe workstation need not be complicated. A protective mat properly tied to ground and a wrist strap are
all that is needed to create a basic anti-ESD workstation (see figure 12-2).