UEi Test Instruments DM384 - Manual (Page 6)

To make capacitance measurements, plug in the test leads as
instructed, then:
1. Discharge the capacitor to be tested as prescribed above.
2. Isolate the capacitor by lifting at least one of its two legs away
from the circuit.
3. Select the capacitance position “ “ on the rotary
function switch.
4. Connect the red test lead to one side of the capacitor, and the
black to the other.
5. Read the measured value.
Note: In the autora n ging mode, it takes approximately 10 seconds to
settle on a value for a capacitor. La rger capacitors re q u i re even more
time. In the manual ra n ging mode, measurements are often faster.
Measuring Resistance
Resistance is the measure of a component’s or circuit’s tendency to
oppose current flow. Because of the many factors that affect resistance,
the most accurate measurements are made when components under
test are isolated from other components or circuits. It is critical to the
accuracy of the measurement that you remove all power to the circuit
when making resistance measurements. If the component or circuit
cannot be isolated, turn off all power sources and discharge all in-circuit
capacitors before attempting the measurement. This meter may be
damaged if more than 600 volts are present.
Note: When measuring critically low ohm values, touch the tips of the
test leads together and record the reading. Subtract this value from the
total resistance of the circuit under test to obtain the actual value.
For resistance measurements above one Megohm the display might take
a few seconds to stabilize. This is normal for high resistance readings.
The voltage or current applied during resistance measurements
could damage some extremely sensitive electronic devices. Typically,
the voltages present at the test leads when making resistance
measurements range from 3 volts at 1.5 mA (in the lowest range)
to .5 volts at <1µA (in the highest range).
To measure the voltage drop on diodes, plug in the test leads as
instructed, then:
1. Turn off the meter.
2. Select the diode test function on the rotary function switch.
3. Connect the red test lead to the anode side of the diode, and the
black to the ca t h o d e .
Note: T h e re is normally a printed black band around the cathode of
a standard diode.
4. Note the displayed value.
5. Reverse the red and black test leads. Again, note the displayed value.
6. If the digital reading in the first (forward biased) direction indicates
some measurable value and the reading in the reverse biased
direction shows an over-range “.OL” the diode is probably good.
7. If the displayed value is low, or all zeros, in both directions, the
diode id probably shorted.
8. If the display indicated an overload “.OL” in both directions, the
diode is probably open (burned out).
Note: Some diodes, such as those used in microwave ovens, require a
higher biasing voltage than this meter supplies. See UEi’s catalog for an
economical high-power diode test lead adapter set if necessary.
Measuring Continuity
Continuity is the measure of a circuit or component’s ability to conduct
electricity. Use this mode to make quick checks for continuity (good
connections) in electrical circuits, such as wiring, speaker cables,
switches, or relays. In the continuity mode an audible tone sounds when
the value measured is approximately 30Ω or less. The resistance of the
circuit (up to 400 ohms) is displayed regardless of the continuity tone.
To measure continuity plug in the test leads as instructed, then:
1. Turn off the meter.
2. Select the continuity “ “ test function on the rotary
function switch.
3. Place one probe to each side of the circuit to be tested. If the circuit
measures approximately 30Ω or less, the meter will sound a
continuous tone.
Measuring DC Voltage
WARNING!
To avoid the risk of electrical shock and instrument damage, input
voltages must not exceed the limits specified for the installation
category you are working in. DO NOT attempt to take any unknown
voltage measurements that may exceed these values.
Note: When taking voltage measurements your meter must be
connected in parallel to the circuit, or circuit element, under test.
To measure DC volts plug in the test leads as instructed, then:
1. Turn off the meter.
2. Select the “DC V” or “DC m V” function on the rotary function switch.
• The DCV position can be used for any DC voltage
measurement
• The DCmV position is ideal for DMM accessories that have a
DC millivolt output
• If you do not know the maximum value of the voltage to be
measured, use the DCV position and allow the meter
to auto-range.
3. Connect the test leads across the test-points of the circuit to be tested.
4. Read the measured voltage on the display.
Note: If the voltage on the red test lead is lower (more negative)
than that on the clack test lead, the negative polarity symbol (a
minus) will appear on the left of the display.
DM384-MAN P. 5