D. AC Curr ent Measurement
Warning – Never attempt an in-circuit curren t measur ement wh ere the voltage b etween ter minals and
round is greater th an 60V or 30V rms.
If the fuse burn s out during measurement, the Meter may be damag ed or th e op erator himself may be
hurt. Disconnect po wer supply b efor e making measur emen t. Use proper ter min als, function, and
range for the measuremen t. W hen the testing leads are con nected to the curren t ter minals, do not
parallel them across an y circui t.
To measure c urrent, do the f ollowing:
11. Turn off power t o the circuit. Disc harge all high-v oltage capacit ors.
12. Insert the red test lead int o the
m A
or
20A
t erminal or
10A
terminal and the black test lead into the
COM
t erminal.
When m eas uring c urrent at 200mA below, insert the red test lead into
mA
t erminal while measuring current
200m A or abov e, insert the red test lead into
10A
or
20A
t erm inal.
13. Set the rotary switch to an appropriate m eas urem ent position in
A
. range.
14. Break the current path t o be tested. Connect the red test lead to the m ore positiv e side of the break and t he black
test lead to the more negativ e side of the break.
15. Turn on power t o the circuit.
The measured v alue shows on the dis play .
Note
l
If the v alue of current to be meas ured is unknown, us e the maximum measurem ent position (20A) and
20A
terminal or (10A) and
10A
terminal, and reduc e the range step by step until a s atisf actory reading is obtained.
l
Replace appropriate rating f use when the fuse is burnt.
Fuse specif ication: 0.315A. 250V fast ty pe f use, Ø 5 x 20 mm.
l
DM39A/ – At 10A R ang e
: For c ontinuous measurement < 10 sec onds and interv al not less than 15 minut es.
l
DM39B– At 20A Range
: For continuous measurement < 10 s econds and int erval not less than 15 minutes.
l
When current m eas urement has been completed, disconnect the c onnection bet ween the testing leads and the
circuit under t est.
