d. Press GO BACK (F2) , then press MORE (F1) to advance
to Manual Test Setup Window 2.
10. Protective Earth
a. Press Protective Earth (F7).
b. Connect the test leads between EARTH and ENCL.
c. Press START (F1). QA-90 will time the measurement and
stop automatically. Take measurements at 0, 100, 500, 1000
and 2000 mΩ with a Metron calibrating unit. Note that the
test current is delivered by a transformer located on the right
side of the cabinet. In low mains voltage, this transformer
will not deliver the IEC/UL-recommended 10 A. If you are
doing repetitive testing and the transformer gets hot, it may
turn off for a while to prevent overheating. It is not rated to
deliver in excess of 25 A in short circuit condition. A trans-
former for 100-120 V mains is available from METRON.
d. Press GO BACK (F2) to return to the previous display.
11. Insulating Resistance. Insulation resistance measurements are
done in both the Mains to Case and Applied Part to Case mod-
es.
a. Ensure the QA-90 is ON for at least 30 minutes.
b. Press Insulating Resistance (F6).
c. Select Mains To Case (F7).
d. Connect a voltmeter or a digital multimeter, with an input
impedance of 10 MΩ, between ENCL. and the mains outlet
on the front panel. Press START (F1).
e. Measure the test voltage.
f. Trim the test voltage to within 500 ± 1 V. Then, use a cali-
brated resistor to measure values in the range 1-200 MΩ.
IMPORTANT
ENSURE THAT THE TEST LEADS ARE CALIBRATED BEFORE
CONDUCTING THIS MEASUREMENT. METRON RECOMMENDS
THAT, WHEN CALIBRATING THE QA-90, TEST LEAD CALIBRA-
TION BE DONE AT LEAST TWICE.
To Next Page
Loading...
Need help?
General
