METRON QA-90, Руководство пользователя и обслуживания

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5-10
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 m
Ω
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 M
Ω
, 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 M
Ω
.
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.