Digital Multimeter (220-0168) Operation Faxback Doc. # 7953
with PC Interface
MAKING MEASUREMENTS
UNDERSTANDING PHANTOM READINGS
In some DC and AC voltage ranges, when the probes are not connected to any
circuit, the display might show a phantom reading. This is normal. The
meter's high input sensitivity produces a wandering effect. When you
connect the probes to a circuit, accurate readings appear.
MEASURING HIGH-VOLTAGE CIRCUITS
When you use the meter to check a high-voltage circuit, do not try to
position both probes at once. Instead, clamp one probe to the neutral or
ground lead of the circuit (usually a bare, green, or white wire in AC
wiring circuits) using insulated Slip-On Alligator Clips (Cat. No.
270-354). Then probe for voltages with the other probe. This helps
prevent you from accidentally touching a hot wire because you need to
concentrate on only one test probe.
Warning: Never clamp onto a hot wire, (usually red, black, or blue in
AC wiring circuits.) If you clamp onto a hot wire and touch the
other probe, you could receive a shock.
AC/DC VOLTAGE MEASUREMENT
WARNING: DO NOT TRY TO MEASURE A VOLTAGE GREATER THAN 1000 VOLTS DC OR
750 VOLTS AC. YOU MIGHT DAMAGE YOUR METER AND EXPOSE YOURSELF
TO A SEVERE SHOCK HAZARD.
Note: All the figures on the display blink when more than the maximum
voltage (DC 1000/AC 750 VOLTS) is supplied. If this happens,
DISCONNECT THE PROBES IMMEDIATELY.
Follow these steps to measure AC/DC voltage.
1. Rotate the function selector to the desired position.
Select the range as required for the voltage level to be measured. If
you do not know the voltage level, start with the range switch set to
the highest voltage position and reduce the setting as needed to get a
reading.
2. Press DC/AC to toggle between DC and AC voltage. AC appears for AC
measurements.
3. Plug the black probe into the meter's COM terminal and the red probe
into the V ohms terminal.
4. Connect the probes to the AC/DC voltage source you want to measure.
Notes: If polarity is negative, - appears on the left of display.
For the most accurate measurement, select the lowest possible
voltage range without getting an overload reading.
Measuring an AC Voltage on a DC Bias
To measure an AC voltage superimposed on a DC voltage source bias, follow
the steps for measuring AC voltage.
Caution: Never try to measure an AC voltage that is riding on a
DC voltage level where the peak AC Voltage exceeds 1000V with
respect to earth ground.
MEASURING 3-PHASE AC VOLTAGES
We designed this meter to measure household AC voltage. It is not
intended for commercial or industrial use. If you want to measure
3-phase, line-to line voltages, please note the following.
Warning: Because of the dangers inherent in measuring three-phase
circuits, we strongly recommend that you do not use the meter
for such applications.
If you choose to make the measurements, use extreme care. The
actual voltage can be greater than the circuit's rated voltage
(line-to-ground).
To determine the line-to-line voltage, multiply the rated
line-to-ground voltage by 1.732.
For example, if the rated line-to-ground voltage is 462 volts,
the line-to-line voltage is:
462 Volts X 1.732=800 Volts
This voltage exceeds the meter's rating and you should not connect the
meter to this circuit. See "Measuring High-Voltage Circuits."
MEASURING AC/DC CURRENT
WARNINGS: DO NOT APPLY VOLTAGE DIRECTLY ACROSS TERMINALS. YOU MUST
CONNECT THE METER IN SERIES WITH THE CIRCUIT.
THE 20A TERMINAL IS FUSED. A SEVERE FIRE HAZARD AND SHORT
CIRCUIT DANGER EXISTS IF YOU APPLY A VOLTAGE WITH HIGH-CURRENT
CAPABILITY TO THIS TERMINAL. THE METER CAN BE DESTROYED UNDER
SUCH CONDITIONS.
To measure current, break the circuit and connect the probes to two
circuit connection points. Never connect the probes across a voltage
source in parallel. Doing so can blow the fuse or damage the circuit
under test.
Note: The maximum input current is 200 mA or 20 A depending on the
terminal used. In these ranges excessive current blows the fuses,
which you must replace.
1. Rotate the function selector to the desired A range. If you do not
know the current level, set it to the highest position and reduce the
setting as needed to get a reading.
2. Press DC/AC to toggle between DC and AC amps.
3. Plug the black probe into your meter's COM terminal and the red probe
into your meter's mA or 20A terminal.
4. Remove power from the circuit under test and then break the circuit at
the appropriate point.
5. Connect the probes in series with the circuit.
6. Apply power and read the current. Your meter displays the current
value.
Note: If you set the meter for DC current, - appears or disappears.
This indicates the polarity of the measured current.
MEASURING CAPACITANCE
Follow these steps to measure normal capacitance.
1. Before testing, discharge each capacitor by shorting its leads
together. Use caution when handling some capacitors, as they can be
charged with considerable electricity.
Caution: If you attempt to measure the capacitance of a charged
capacitor, you might damage your meter.
2. Rotate the function selector to the desired CAP range (LO for
low-value capacitors and HI for High-value capacitors). If you do not
know the approximate capacitance value, set the range to HI and
reduce to LO to get a valid reading.
3. Insert the discharged capacitor into the CAP connectors. Your meter
displays the capacitance values.
Notes: For polarized capacitors, be sure to insert the negative lead in
the -clip.
In this mode's HI range, the auto power off function does not
work.
MEASURING RESISTANCE
WARNINGS: NEVER CONNECT THE TEST PROBES TO A SOURCE OF VOLTAGE WHEN YOU
HAVE SELECTED THE OHMS FUNCTION AND PLUGGED THE PROBES INTO THE
V/OHMS TERMINAL.
BE SURE THAT THE CIRCUIT UNDER TEST HAS ALL POWER REMOVED AND
THAT ANY ASSOCIATED CAPACITORS ARE FULLY DISCHARGED BEFORE YOU
MAKE A RESISTANCE MEASUREMENT.
The resistance measuring circuit compares the voltage gained through a
known resistance (internal) with the voltage developed across the unknown
resistance. So, when you check in-circuit resistance, be sure the circuit
under test has all power removed (all capacitors are fully discharged).
1. Plug the black probe into your meter's COM terminal and the red probe
into your meter's V/OHM terminal.
2. Rotate the function selector to the desired OHM range.
3. Connect the probes to the device you want to measure.
Notes: If the measured resistance value exceeds the maximum value of the
range selected, OL appears and the bargraph flashes. This
indicates an overload. Select a higher range. In this mode, the
beeper does not sound.
When you short the test probes in the 200 OHM range, your meter
displays a small value (no more than 0.3 ohms). This value is due
to your meter's and test lead's internal resistance. Make a note
of this value and subtract it from small resistance measurements
for better accuracy.
For resistance of about 1 Megohm and above, the display might take
a few seconds to stabilize. This is normal for high-resistance
readings.
CHECKING DIODES
This function lets you check diodes and other semiconductors for opens and
shorts. It also lets you determine the forward voltage for diodes. You
can use this function when you need to match diodes.
1. Plug the black probe into your meter's COM terminal and the red probe
into your meter's V/OHMS terminal.
2. Rotate the function selector to the diode position.
3. Connect the probes to the diode you want to check and note the meter
reading.
If the display shows a value, for example 0.2 for a geranium diode or
0.5 for a silicon diode, reverse the diode. If the meter indicates an
overrange, the diode is good. The displayed number is the diode's
actual forward voltage (up to 2.0 volts).
If the display indicates an overrange condition, reverse the polarity
of the connection. If the display shows a value, the device is good.
The displayed value is the component's actual forward voltage (up to
2.0 volts). If the display still indicates an overrange condition,
the device is open.
If the display shows a value both before and after you reverse the
polarity, the device is shorted.
When you connect the diode to the meter and the meter displays the
device's forward voltage, the red test probe or socket is connected to the
diode's anode, and the black probe or socket is connected to the diode's
cathode. This meter supplies enough forward voltage to light most LEDs.
However, if the LED's forward voltage is greater than 2.0 volts, the meter
incorrectly indicates that the device is open.
CHECKING CONTINUITY
Follow these steps to check a circuit's continuity.
1. Rotate the function selector to MUSIC SYMBOL.
2. Plug the black probe into your meter's COM terminal and the red probe
into your meter's V/OHM terminal.
3. Remove power from the circuit.
Warning: Never perform a continuity measurement on a circuit that has
power connected.
4. Connect the probes to the circuit.
Note: The buzzer sounds if the measured resistance is below 40 ohms.
CHECKING TRANSISTORS
Follow these steps to determine a transistor's base gain.
1. Rotate the function selector to the hFE position.
2. Insert the transistor you want to measure into the appropriate
transistor socket. Your meter displays the transistor's hFE value.
Notes: Insert the base, collector, and emitter pins in the correct
sockets, as marked.
Do not take the hFE reading as an absolute measurement, but
rather as an indication that the transistor is operating. The
true gain of a transistor depends on its operating current. This
meter applies 500 to 1000 microA to the emitter and collector and
measures the base current to calculate the base gain.
Even though the meter turns off the test probes during the hFE
measurement, a voltage connection might affect the hFE reading.
Do not connect the test probes to a voltage source during this
measurement.
You cannot measure the hFE of a transistor that is connected in
a circuit.
You cannot measure the hFE of an FET or other non-bipolar
transistor.
Some power Darlington transistors contain an internal base-to-
emitter resistor. Because the meter uses two current readings to
calculate hFE, any internal transistor resistance causes
undependable readings.
High-voltage junctions in power transistors prevent correct
readings. Also, the larger leads of the power transistor can
damage the test socket.
Do not try to determine hFE for power transistors with this meter.
hFE is affected by temperature. Try not to warm the transistor
with your hand when you install the device in the socket. If the
hFE reading is not stable when you first measure it, let the
transistor's temperature stabilize.
Warning: The transistor socket is not protected against overload.
You can damage the meter and void your warranty if you
build and use external leads for the transistor socket.
MEASURING FREQUENCY
WARNING: IF YOU TRY TO MEASURE THE FREQUENCY OF A SIGNAL THAT EXCEEDS 250
VOLTS AC RMS, YOU MIGHT DAMAGE YOUR METER AND EXPOSE YOURSELF TO
A SEVERE SHOCK HAZARD.
Follow these steps to measure the frequency of a signal.
1. Rotate the function selector to FREQ.
2. Plug the black probe into your meter's COM terminal and the red probe
into your meter's V/OHM terminal.
3. Connect the probe to the frequency source.
Notes: Input limit voltage: AC 250 V max.
Input sensitivity:
1 Hz up to 1 MHz - 150 mV rms.
1 MHz up to 20 MHz - 300mV rms.
Warning: When you connect the test probes to an AC outlet, do not turn
the function selector switch to another range. It could damage
the meter's internal components or injure you.
LOGIC TEST
The logic function lets you easily check digital circuits to determine the
logic state of different parts of the circuit. Rather than display an
absolute voltage, this function displays HI, LO, or--- to indicate logic
high, logic low, or undetermined, respectively.
Follow these steps to perform a logic test.
1. Rotate the function selector to the HIGH/LOW logic range.
2. Plug the black probe into your meter's COM terminal and the red probe
into your meter's V/OHM terminal.
3. Connect the black probe to the ground point (GND of the test circuit
and the red probe to the supplying voltage point (V+). While keeping
the test probes firmly connected to each point, press SET/RESET.
4. While keeping a connection between the black probe and the circuit's
GND point, move the red probe to the other desired points. The meter
immediately displays one of the three indications.
If the measured value exceeds 70% of the stored (V +) value, Hi (HIGH)
appears.
If the measured value is between 30% and 70% of the stored (V +)
value, --- appears.
Notes: In this mode, the Data-Hold and Max/Min-Hold functions do not
work (See "Using the Advanced Functions").
The logic level is limited to a voltage range of 0.5 V
to 19.9V.
(br/all-01/17/95)
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