Associated Research HypotULTRA II 7500DT, Руководство по эксплуатации и обслуживанию

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INTRODUCTION
12
The Ground Bond Test
The Ground Bonding test determines whether the safety ground circuit of the product
under test can adequately handle fault current if the product should ever become defective.
A low impedance ground system is critical in ensuring that in the event of a product failure
a circuit breaker on the input line will act quickly to protect the user from any serious
electrical shock.
International compliance agencies such as CSA, IEC, TÜV, VDE, BABT and others, have
requirements calling out this test. This test should not be confused with simple low
current continuity tests that are also commonly called out in some safety agency
specifications. A low current test merely indicates that there is a safety ground
connection, it does not completely test the integrity of that connection.
Compliance agency requirements vary on how different products are to be tested. Most
specifications call for test currents of between 10 and 30 amps. Test voltages at these
currents are typically required to be less than 12 volts. Maximum allowable resistance
readings of the safety ground circuit are normally between 100 and 200 milliohms.
The 7504SA provides up to 30 amps output current at any voltage between 3 and 8 volts
through the safety ground of the product under test. Simultaneously the instrument
measures the induced voltage across the safety ground circuit to determine the impedance
of the ground connection. The meter displays the resistance reading of the ground circuit
in milliohms.
The measured values are typically very low so it is extremely important to avoid reading
the resistance of the test leads that are used to connect the test instrument to the product
under test. If this is not done a device may be tagged as having a safety ground failure
when it is actually the combined resistance of the DUT and the test leads that has caused
the maximum resistance level to be exceeded. The 7504SA milliohm offset feature can be
adjusted to disregard the resistance of the test leads.
IF YOU SHOULD HAVE ANY QUESTIONS RELATING TO THE OPERATION
OF YOUR INSTRUMENT CALL 1-800-858-TEST(8378) IN THE U.S.A.