The Different Types Of Safety Tests - Extech Instruments 7470 Operation Manual

the Association of German Electrical Engineers (VDE) and (TÜ V), the Japanese
Standards Association (JSI). These same agencies may also require that an
insulation resistance test and high current ground bond test be performed.

1.6. The Different Types of Safety Tests

1.6.1. Dielectric Withstand Test
The principle behind a dielectric voltage – withstand test is simple. If a product will
function when exposed to extremely adverse conditions, it can be assumed that the
product will function in normal operating circumstances.
Common Applications of the Dielectric Withstand Test:
 Design (performance) testing: Determining design adequacy to meet service
conditions.
 Production Line testing: Detecting defects in material or workmanship during
processing.
 Acceptance testing: Proving minimum insulation requirements of purchased parts.
 Repair Service testing: Determine reliability and safety of equipment repairs.
The specific technique used to apply the dielectric voltage – withstand test to each
product is different. During a dielectric voltage – withstand test, an electrical device is
exposed to a voltage significantly higher than it normally encounters, for a specified
duration of time.
During the test, all current flow from the high voltage output to the return is measured.
If, during the time the component is tested, the current flow remains within specified
limits, the device is assumed safe under normal conditions. The basic product design
and use of the insulating material will protect the user against electrical shock.
The equipment used for this test, a dielectric-withstand tester, is often called a "hipot"
(for high potential tester). The "rule of thumb" for testing is to subject the product to
twice its normal operating voltage, plus 1,000 volts.
However, specific products may be tested at much higher voltages than 2X operating
voltages + 1,000 volts. For example, a product designed to operate in the range
between 100 to 240 volts can be tested between 1,000 to 4,000 volts or higher. Most
"double insulated" products are tested at voltages much higher than the "rule of thumb".
Testing during development and prototype stages is more stringent than production run
tests because the basic design of the product is being evaluated. Design tests usually
are performed on only a few samples of the product. Production tests are performed
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