
3. Setting Up and Running a Test
72A-2570-01 Rev. K 07/2011
3-23
Excessive ground-loop resistance affects the shape of the traces,
especially at higher frequencies. Acceptable values depend on lead
length:
•
18 m (60 ft) leads—A value of less than 1 ohm is ideal. Attempt to
clear the alert by checking all ground connections and restarting
the test. Continuing to test with ground resistance above 1 ohm
may compromise the results.
•
30 m (100 ft) leads—Results are normally as high as 1.5 ohms; if
the resistance shown is below 1.5 ohms, continue the test. If the
resistance shown exceeds 1.5 ohms, check all ground connections
and restart the test. Continuing to test with ground resistance
above 1.5 ohms may compromise results.
Causes of high ground-loop resistance include poor connections to
bushing studs because of dirt, grease, or paint, or, occasionally, the
stud itself not being grounded. Consider any measurement above
250 ohms an open circuit. If Alert 952 occurs, ensure that all
connections are good.
•
Error 953—The internal M5000 performance check was
unsuccessful (
Figure 3.37 Error 953
The instrument generates signals at a number of frequencies and
measures them without sending them through the test object. This
signal verification test confirms that the device is performing as
expected. If the test fails, results will be compromised.
You are not
allowed to continue the test.
Contact Doble Engineering for
troubleshooting and repair.
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