Urrea UD112, User'S Manual And Warranty Information

Page: 22 / 32

E N G L I S H
22
Resistance is an opposition to current flow.
The unit of resistance is the Ohm (Ω). The
multimeter measures resistance by sending
a small current through the circuit.
Ranges available in resistance functions are:
400.0 Ω, 4.000 kΩ, 40.00 kΩ, 400.0 kΩ, 4 MΩ,
and 40 MΩ.
Tips for measuring resistance
• Because the meter’s test current flows
through all possible paths between the
test probe tips, the measured value of a
resistor in a circuit is often different from
the resistor’s rated value.
• The test leads can add 0.1 Ω to 0.2 Ω of
error to resistance measurements. To
measure the resistance of the leads, touch
the probe tips together and read the
resistance. If necessary, you can press the
button to automatically subtract
this value.
• The resistance function can produce
enough voltage to forward-bias silicon
diode or transistor junctions, causing them
to conduct. Do not use the 40 MΩ range
for measuring the in-circuit resistance to
avoid this.
• When measuring large resistance, reading
may be unstable due to environmentally
induced electrical noise. In this case,
directly connect the resistor to input
terminals of the meter or shield the
resistor at the potential of the COM input
terminal to obtain stable reading.
• For resistances above 1 MΩ, the display
may take a few seconds to stabilize. This
is normal due to high resistance readings.
• The meter has a circuit to protect the
resistance range from over-voltage.
However, to prevent accidentally
exceeding the protection circuit’s rating
and to ensure a correct measurement,
NEVER CONNECT THE LEADS TO A SOURCE
OF VOLTAGE when the rotary switch is set
to Ω or or functions.
Diode ( ) Test
CAUTION: DISCHARGE ALL HIGH-VOLTAGE
CAPACITORS BEFORE TESTING DIODES. LARGE
VALUE CAPACITORS SHOULD BE DISCHARGED
THROUGH AN APPROPRIATE LOAD RESISTANCE.
Use the diode test to check diodes,
transistors, silicon controlled rectifiers
(SCRs), and other semiconductor devices.
The test sends a current through a
semiconductor junction, then measures the
junction’s voltage drop.
Normal forward voltage drop (forward
biased) for a good silicon diode is between
0.4 V to 0.9 V. A reading higher than this,
means a leaky (defective) diode. A zero
reading indicates a shorted (defective)
diode.
An indicates an open diode (defective).
Reverse the test leads connections ( reverse
biased ) across the diode.
The display shows if the diode is in good
conditions. Any other readings indicate the
diode is shorted or resistive ( defective ).
Continuity ( ) Test
The continuity function detects intermittent
opens and shorts lasting as little as 1
millisecond.