INTRODUCTION
Static fields can build up on humans as they walk along an insulative surface such as a carpet. A person with a high voltage static
charge can destroy or damage an integrated circuit or FET device either by touching or coming close to it. Thus most electronic
assemblers wear wrist straps or heel grounders to keep the wearers at the same voltage potential as the parts they are assembling.
Wrist straps and heel grounders may also be worn at chemical plants, explosive materials factories and storage areas. A wrist
strap is simply a resistorized conductive cord that connects the wearer’s wrist to a grounded conductive mat that covers the
assembly bench. The resistor protects the static sensitive device as well as the worker.
A heel grounder is a small resistorized strap that connects the wearer to their special conductive floor surface. This requires that the
floor be covered with a grounded conductive carpet, tile, mat or dissipative floor wax or paint (available through Static Solutions). It
is important that two heel grounders be worn to achieve proper static discharge.
Wrist straps and heel grounders simply act as a wire to drain off charges. However, to prevent accidental electrocution of the
wearer (should the wearer inadvertently touch an external high voltage source) a high resistance is built into the strap. The
resistance is typically between .5 to 2 megohms.
Thus straps and heel grounders have to be tested for two different malfunction conditions. If there is an open circuit (too high a
resistance), and does not function, then it will fail to prevent high voltage build up. If there is a short circuit (too low a resistance),
then it will fail to prevent electrocution.
The Wrist Strap and Dual Heel Tester is a small handheld or wall mounted instrument that checks the conductive integrity of wrist
straps and heel grounders. This prevents faulty straps from allowing high voltage buildup on the wearer, and prevents short-
circuited straps from enabling electrocution of the wearer.
To use it, the wearer simply inserts their wrist strap plug into the instrument, and stands on the foot plates (if wearing heel
grounders or shoes), and presses the button. An LED display shows the results of the test (OK, low or high), and an alarm sounds if
the resistance is not within its preset limits..
Static Solutions CT-8700 Combo Tester Instructions
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6/22/2008
