Ac/Dc Current Measurement; Resistance Measurement - UNI-T UT39B Manual

B. DC/AC Current Measurement
• Never attempt an in-circuit current measurement where the voltage between terminals and
ground is greater than 60V DC or 30V rms.
• If the fuse burns out during measurement, the Meter may be damaged or the operator himself
may be hurt. Use proper terminals, function, and range for the measurement.
• When the testing leads are connected to the current terminals, do not parallel them across any
circuit.
• Measuring time for current should be less than 10 sec and interval between measurement
should be at least 15 minutes.
To measure current, do the following:
1. Turn off power to the circuit. Discharge all high-voltage capacitors.
2. Insert the red test lead into the A or mA terminal and the black test lead into the COM termi-
nal.
3. Set the rotary switch to an appropriate measurement position A = for DC or A~ for AC. When
the value is unknown always start from the max range 20 A.
4. Break the current path to be tested. Connect the red test lead to the more positive side of the
break and the black test lead to the more negative side of the break.
5. Turn on power to the circuit. The measured value shows on the display.
If the value to be measured is unknown, use the maximum measurement position and reduce the
range step by step until a satisfactory reading is obtained.
C. Resistance Measurement
To avoid damages tot the meter or to other devices under test, disconnect circuit power and dis-
charge all the high voltage capacitors before measuring resistance.
To measure connect the meter as follows:
1. Insert the red test lead into the VW terminal and the black test lead into the COM terminal.
Set the rotary switch to an appropriate measurement position W range.
2.
3. Connect the test leads across with the object being measured. The measured value shows on
the display.
For high resistance measurement (>1MW) it is normal to take several seconds to obtain a stable
reading.
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