INTRODUCTION
4
the case of a grounded part the conductive table or conveyor should not be touched
during a test.
Several models of high voltage test equipment are designed with the high voltage output
"floating". There is no ground on either the High side or the Low side of the high voltage
transformer. One of the test leads of the HV transformer is considered the Low side due
to the winding pattern of the transformer, but it is NOT grounded. This arrangement
provides a one type of safety margin to the operator because someone must come in
contact with both leads to receive a shock.
Some models of test equipment have one lead of the output grounded or production
requirements are such that it is impossible or impractical to test a product in an
"ungrounded" configuration. When the tester and the product are grounded, it is
important to remember that the operator is also grounded and need only touch the
ungrounded lead to receive a shock.
A major consideration in testing products that are "grounded" (touching a conductive
conveyor or table) is to insure that the operator or bystanders cannot or will not come in
contact with the table or conveyor during a test. Under some product failure conditions,
the table or conveyor may become "live" and present a high voltage potential to true earth
ground if the table or conveyor is not properly grounded.
It should never be assumed that a conveyor or conductive table is "grounded" just because
it is bolted to the floor. A proper ground is one that has been verified to return to the
input power line ground (earth ground) with a resistance of less than 1/2 ohm. This will
help eliminate "floating" grounds, ground loops and "phantom" voltages between the
object under test and the tester case which is grounded to the power line ground.
The testing of very large items such as recreational vehicles and mobile homes poses
special problems because the safety hazards involved are considerably greater than those
involved in testing smaller objects.
This is because it is possible under fault conditions for the entire outer skin of the object
being tested to become charged to a high voltage. This is particularly bad because these
units are so large that the person conducting the test is in no position to observe whether
or not any other people are in a potentially dangerous position during the test.
If proper precautions are taken, there will be no hazard, but even so, it is highly desirable
that care be taken to isolate the test object when a test is being conducted. Suggested
methods of doing this are the use of rope barriers, warning signs, and fully enclosed test
areas.
Before conducting a test on these units, care should be taken to see that the frame and
skin of the unit are connected to a solid ground, and also that the ground conductor of the
electrical system is connected to a solid ground. This will eliminate most test hazards, but
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