True RMS Multimeter (220-0175A) Making Measurements Faxback Doc. # 7244
UNDERSTANDING PHANTOM READINGS
If you do not connect the meter's probes to a circuit, and set it to DC or
AC VOLTS, the display might show a phantom reading. This is normal. The
meter's high input sensitivity produces a wandering effect. When you
connect the test probes to a circuit, a real measurement appears.
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 lead 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
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.
OVERRANGE INDICATION
The following display appears when the measurement exceeds the meter's
range. If you are measuring volts or amps, disconnect the meter from the
circuit you are measuring or change the meter's measuring range. See
"Manually Selecting the Range."
MEASURING DC VOLTAGE
WARNING: DO NOT TRY TO MEASURE A VOLTAGE GREATER THAN 1000 VOLTS DC. YOU
MIGHT DAMAGE THE METER AND EXPOSE YOURSELF TO A SEVERE SHOCK
HAZARD.
Follow these steps to measure a DC voltage.
1. Press VOLTS/AMPS to select voltage measurements. mV appears on the
display.
2. Press AC/DC to select DC measurements.
3. Plug the red test lead into the V Hz terminal, and plug the black test
lead into the COM terminal.
4. Connect the probes to the circuit you want to test.
When you measure DC voltages, the minus sign appears if you connect the
black probe to a point in the circuit that has a higher voltage potential
than the point where you connect the red probe.
Note: The meter does not measure DC using dBm. If you try to select dBm,
the meter switches to AC measurements.
MEASURING AC VOLTAGE
WARNING: DO NOT TRY TO MEASURE A VOLTAGE GREATER THAN 750 VOLTS AC. YOU
MIGHT DAMAGE THE METER AND EXPOSE YOURSELF TO A SEVERE SHOCK
HAZARD.
Follow these steps to measure AC voltage.
1. Press VOLTS/AMPS to select voltage measurements. mV appears on the
display.
2. Press AC/DC to select AC measurements. [AC] appears on the display.
3. Plug the red test lead into the V Hz terminal, and plug the black test
lead into the COM terminal.
4. Connect the probes to the circuit you want to test.
5. To change the readout to dBm, press dBm/Hz. The display changes to
show the reading in dBm. dBm replaces mV on the display.
To return to a voltage display, press VOLTS/AMPS. The meter displays the
measurement in volts.
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 an AC voltage.
Caution: Never try to measure an AC voltage that is riding on a DC
voltage level where the peak AC voltage exceeds 1000 V 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:
Because of the dangers inherent when you measure three-phase circuits,
we strongly recommend you do not use this meter for such applications.
If you choose to make the measurements, use extreme care. The actual
voltage can be greater than the circuits 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 voltage is 462 volts, the line-to line voltage
is:
462 Volts x 1.732 = 800 Volts.
This voltage exceeds the meter's range 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 THE 10A, 400mA, or
Ohms/micro.mA TERMINALS. YOU MUST CONNECT THE METER IN SERIES
WITH THE CIRCUIT.
THE 10A TERMINAL IS NOT 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 in series
with the circuit. Never connect the leads across a voltage source (in
parallel). Doing so can blow the fuse or damage the circuit under test.
The maximum current input limit is 10A.
1. Press VOLTS/AMPS to select amps. microA appears on the display.
2. Press AC/DC to select DC or AC current measurement.
3. Repeatedly press VOLTS/AMPS to set the range. Each time you press
VOLT/AMPS, the range changes.
To measure a current that is less than or equal to 4000 microA (4000
microA (4.000 mA), plug the red test lead into the Ohms/micro.mA
terminal.
To measure a current between 4.000 mA and 400.0 ma, press VOLTS/AMPS
again to select the 40.0 mA or 400.0 mA scale and plug the red test
lead into the 400mA terminal.
To measure a current greater than 400.0 mA, press VOLTS/AMPS again to
select the 4.000 A or 10.00 scale and plug the red test lead into the
10A terminal.
Note: If you are not sure how much current the circuit you are testing
draws, start with the 10A range.
4. Remove power from the circuit under test. Then, break the circuit at
the appropriate point.
5. Connect the probes in series with the circuit.
6. Apply power to the circuit.
7. If the measurement is greater than the selected range, the meter
displays the overrange indication. (See "Overrange Indication."
Press VOLTS/AMPS to select a higher range, and plug the red test lead
into the appropriate terminal.
Notes: If you set the meter for DC current, the (-) sign appears or
disappears to indicate the polarity of the measured current.
The 400 mA and the 4000 microA ranges are fuse-protected. The 10A
range is not fuse-protected.
If the meter blows a fuse while you measure current, the meter
displays the overrange indication or 0.
If the meter displays the overrange indication when you measure AC
current, and the circuit does not exceed the AC current in the
present range, the circuit is exceeding the meter's DC rating.
For example, if you try to measure a DC power supply's AC ripple current,
the signal has both an AC and DC component. If the DC component exceeds
the meter's rating, the meter displays the overrange indication. To
measure this current, you must externally block the DC component.
MEASURING RESISTANCE
WARNINGS: NEVER CONNECT THE TEST PROBES TO A SOURCE OF VOLTAGE WHEN YOU
HAVE SELECTED THE OHMS FUNCTION AND PLUGGED THE LEADS INTO THE
OHMS/micro.mA 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 incircuit resistance, be sure the circuit
under test has all power removed (all capacitors are fully discharged).
1. Press OHMS/CONT. M OHMS appears in the display. If there is no
resistance connected to the meter, the meter sets itself to the
highest measurement range and displays the overrange indication.
2. Plug the red test lead into the OHMS/micro.mA terminal and the black
test lead into the COM terminal.
3. Connect the probes across the circuit to be measured or plug the
resistor under test into the OHMS/DIODE/CAP socket.
If the resistance is greater than 1 megohm, the display takes a few
seconds to stabilize. This is normal for high-resistance measurements.
Notes: The meter has a fuse and a special circuit that protects the
resistance ranges from over-voltage (voltages greater than 5
volts). If you blow the meter's fuse, the meter does not operate
correctly in the Ohms mode. Check the fuse if the meter displays
0 for all resistance measurements.
When you measure the resistance of a component in a circuit,
disconnect one side of the component you are testing. This
prevents other components in the circuit from affecting the
reading.
When you touch the probe ends together, the meter selects the
400-ohm scale and displays a small value. This value is the
resistance of the test leads. Note this value and subtract it
from the measured value when you measure a very small resistance.
You can also use the relative function to compensate for the
resistance. See "Using the Relative Function."
When you measure resistances greater than 400 K ohms, your skin's
resistance can affect the reading. Use the OHMS/DIODE/CAP socket
to measure loose resistors, if possible. If you must hold the
resistor and use the probes, do not touch both probes while you
take a measurement.
Checking Continuity
Follow these steps to check a circuit's continuity:
1. Press OHMS/CONT so that [CONT] and OHMS appear in the display. The
meter sets itself to the 400-ohm resistance range.
2. Connect the red test lead to the Ohms/micro.mA terminal and the black
test lead to the COM terminal.
3. Connect the probes to the circuit you want to test.
If the circuit's resistance is less than or equal to 50 ohms, the buzzer
sounds. If the resistance is greater than 50 ohms, but less than 400
ohms, the meter displays the circuit's resistance and the buzzer does not
sound. The meter indicates an overrange condition if the resistance is
400 ohms or greater.
Notes: The beep sounds even if you turn off the beep option.
If the meter performs a battery check while the continuity tone is
sounding, the tone stops for about 1/2 second.
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. Press DIODE/CAP so that RIGHT ARROW appears in the display.
2. Plug the red test lead into the RIGHT ARROW terminal and the black
test lead into the COM terminal.
3. Remove power from the circuit under test.
4. Connect the probes to the component you want to check or plug the
component into the OHMS/-DIODE/CAP socket. If the diode is banded,
connect the banded end to the black test probe or the -OHMS/DIODE/CAP
socket. Then, note the display.
If the display shows a value, for example, 0.2 for a germanium
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 2.5 volts).
If the display indicates an overange 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 2.5 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
polarity, the device is shorted or the meter's .063-amp fuse is
blown.
When you connect the diode to the meter and the meter displays the
device's forward voltage, the red test lead or + OHMS/DIODE/CAP socket is
connected to the diode's anode, and the black lead or - OHMS/DIODE/CAP
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 2.5 volts, the meter
incorrectly indicates that the device is open.
The bar graph shows a maximum reading of 24, even during an overrange.
CHECKING TRANSISTORS
Follow these steps to determine a transistor's pinout, type, and base
gain.
1. Plug a transistor into the hFE socket.
2. Press hFE. hFE appears in the display.
The meter displays the transistor type (NPN or PNP) for several
seconds.
Then, the meter displays the transistor's pinout. The three letters
it displays correspond to the three terminals of the hFE socket. For
example, if the meter displays EbC, the far left lead is the emitter,
the middle lead is the base, and the far right lead is the collector.
After a short pause, the meter displays the transistor's hFE. This
value ranges from 1 to 39.999.
The meter continuously displays the hFE. If you plug in another
transistor, it displays that transistor's hFE, if it is of the same
type and has the same pinout. To force the meter to re-examine the
transistor type and pinout, press hFE after you install a new
transistor.
Notes: 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 leads during the hFE
measurement, a voltage connection might affect the hFE reading.
Do not connect the test leads 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 a FET or other non-bipolar
transistor.
Some power darlington transistors contain internal base-to-
emitter resistors. 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 type, pin out,
and hFE for power transistors with this meter.
The meter displays a default junction type and pinout if you
press hFE when you have not connected a transistor. The meter
defaults to PNP and CEB with the hFE measurement given as a very
large value or overflow condition. The bar graph reading is not
stable-it ranges up and down while the display maintains a running
average of the random readings.
Since the hFE measurement is an auto-ranging type measurement, you
cannot use the MIN/MAX and relative options while in hFE mode.
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 over-voltage.
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
750 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. Press dBm/Hz.kHz appears in the display.
2. Plug the red test lead into the V Hz terminal and the black test lead
into the COM terminal.
3. Connect the black probe a ground reference for the signal, and connect
the red probe to the signal source.
The meter displays the measured frequency.
Notes: Because measuring frequencies takes several seconds, the
keyboard might be slow to respond to key presses.
The meter uses a 1 Hertz gate signal to measure the frequency of
signals below 4000 Hz. You might have to wait a few seconds for
the display to stabilize.
For signals above 4000 Hz, you might have to manually set the
frequency range to prevent the meter from displaying a harmonic
of the actual frequency. See "Manually Selecting the Range."
The meter does not beep when it updates MIN/MAX when you measure
frequency, even if you have turned on the beep option.
MEASURING CAPACITANCE
Follow these steps to measure capacitance.
1. Press DIODE/CAP. nF appears on the display.
2. Plug the red test lead into the -l(-terminal and plug the black
test lead into the COM terminal.
3. Fully discharge the capacitor.
4. If you are checking an electrolytic capacitor, attach capacitor's +
side to the red probe or plug into the + OHMS/DIODE/CAP socket. Then,
attach the capacitor's - side to the black probe or to the -
OHMS/DIODE/CAP socket.
For other capacitor types, connect the probes to the capacitors leads.
Polarity does not affect the measurement of non-electrolytic
capacitors. Or, install the capacitor in the OHMS/DIODE/CAP socket.
Observe polarity (+ and -) when you measure electrolytic capacitors.
Notes: If you use the test probes, do not touch the probes while you are
checking the capacitor. Your body's capacitance can affect the
measurement
An electrolytic capacitor's measured capacitance changes depending
upon the voltage applied to the capacitor. Because this meter
cannot use rated voltages to set the electrolyte, it cannot
measure the absolute capacitance value.
The lowest capacitance ranges might be offset by the meter's and
test leads' capacitance. When you measure very small-value
capacitors, we suggest you use the relative function to subtract
the internal capacitance from the measurements. See "Using the
Hold/Relative Function."
USING THE MIN/MAX MEMORY FUNCTIONS
The MIN/MAX feature lets you track the high and low values for a changing
measurement. Follow these steps to store the high and low readings.
1. Press MIN/MAX. The meter displays MIN and displays the lowest
measured reading. The meter updates the display as the reading
changes.
Note: Even though the meter only displays MIN, it stores both the minimum
and maximum readings.
2. To display the maximum measured reading, press MIN/MAX again. The
meter displays MAX and the highest measured reading. The meter
updates the display as the reading changes.
Note: Even though the meter only displays MAX, it stores both the minimum
and maximum readings.
3. To display the actual reading, and record maximum and minimum
readings, press MIN/MAX again. The meter displays MIN and MAX.
Press MIN/MAX to switch between viewing the stored minimum value, the
stored max. value, and the current value.
4. To clear the minimum and maximum measurements, press and hold down
HOLD/RELATIVE for about 2 seconds.
5. To exit the MIN/MAX mode, select any other function.
Notes: If you press BEEP to turn the beep feature on or off, the meter
exits the MIN/MAX mode.
You cannot use the MIN/MAX mode and the relative mode at the same
time. If you select the relative mode, the MIN/MAX function turns
off. If the relative mode is already active, the meter ignores
the MIN/MAX key.
The meter exits the MIN/MAX mode if you try to measure a value
that is outside the current range or if you manually change the
range.
Comparing Components
When you use the diode, resistance, or continuity modes, the meter
indicates an overrange condition if you have not connected a component.
To use the MIN/MAX function in these modes to check the values of several
components, use the hold function to prevent an overrange condition
between measurements.
1. Insert the component in the Ohms/DIODE/CAP socket or attach the leads
to the component. If you are checking diodes, be sure to connect the
cathode to the black test probe or-OHMS/DIODE/CAP socket.
2. Press AUTO/MAN to set the meter to the manual range mode, and set the
meter to the appropriate range.
3. Press MIN/MAX to enter the MIN/MAX mode.
4. Before you remove the component, press HOLD RELATIVE to hold the
current reading. This prevents the meter from registering an overflow
condition when you remove the component.
5. Remove the component, and connect the next component you want to
measure.
6. Press HOLD RELATIVE to release hold and measure the component.
7. Repeat Steps 4 and 5 until you have measured all components.
8. To recall the minimum and maximum measured values, repeatedly press
MIN/MAX. When MIN appears on the display, the meter displays the
minimum measured value. When MAX appears on the display, the meter
displays the maximum measured value.
USING THE HOLD FUNCTION
The hold function lets you hold the current reading on the meter's
display.
During any reading, press HOLD/RELATIVE to prevent changes in the measured
value from updating the display. The meter displays HOLD. Press HOLD.
Press HOLD/RELATIVE again to resume normal operation.
USING THE RELATIVE FUNCTION
The relative feature lets you set a reference measurement and measure
additional values relative to the reference. For example, if you set the
reference at 100 ohms, the meter would display a 123-ohm resistor as
23 ohms, and would display a 75-ohm resistor as -25 ohms.
Follow these steps to set a reference.
1. Make a reference measurement.
2. While you measure the reference value, press and hold down
HOLD/RELATIVE for about 2 seconds. The meter beeps. After 2 seconds,
the meter displays REL and sets the reading to 000.
The meter displays additional measurements relative to the reference
value. The meter displays values greater than the reference as
positive values and values less than the reference as negative values.
Note: You cannot use the MIN/MAX mode and relative mode at the same time.
USING THE BAR GRAPH
In addition to the numeric display, the meter displays all measurements on
a bar graph at the bottom of the display. The bar graph is updated more
quickly than the digital display, and gives a better indication of levels
and trends for varying measurements. The bar graph has 41 marks. The
first mark is always on, and indicates 0. Each additional mark represents
the first two digits in the display.
For example, if the displayed value is 1.853, 19 marks appear on the bar
graph.
For DC functions, a negative sign appears to the left of the bar graph to
indicate negative polarity.
MANUALLY SELECTING THE RANGE
The meter automatically selects the best range for most applications. For
some situations, you might want to manually set the range. To switch to
the manual mode, press AUTO/MAN so that AUTO disappears from the display.
Then, press RANGE UP ARROW or RANGE DOWN ARROW to select the range.
To return to automatic range selection, press AUTO/MAN so that AUTO
appears on the display.
USING THE BEEP OPTION
You can have the meter beep when any of the following occurs:
In the MIN/MAX mode, when the meter updates the minimum or maximum value
When the meter automatically changes measurement ranges
When you press one of the mode buttons
To have the meter beep, press BEEP so that BEEP appears on the display.
To cancel the beep option, press BEEP again. BEEP disappears from the
display.
The meter always beeps in the continuity mode and when you switch to the
relative mode.
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