A digital multimeter, or DMM, is a device that can
measure multiple electrical values, such as voltage,
current, resistance, frequency, capacity, or
temperature. It has probes, clamps, or leads that
connect to the device under test. It shows the
measured values as numerical values on a digital
display. Some digital multimeters can select the
measurement range automatically. It is a standard
diagnostic tool for technicians and electrical
Why are digital multimeters used?
• A DMM is primarily used to verify one of the three factors of Ohm’s
Law voltage (volts), current (amps) and resistance (ohms). This
simple equation, expressed below, is commonly used by electrical
engineers during diagnostic testing.
• V = I x R
where V = voltage, I = current, R = resistance
• Engineers in the lab and in the field also use digital multimeters to
verify the state of a system or circuit for safety purposes. For
instance, voltages in excess of 42V or currents in excess of 10 mA
can provide painful shocks, and in some cases, be lethal.
Resistances are also rated for certain powers (watts) and can get
hot when driving higher currents and voltages. Digital multimeters
essentially help engineers verify that a device under test is safe to
Types of digital multimeters
• General purpose digital multimeter
• Handheld digital multimeter
• Advanced digital multimeter
• Compact digital multimeter
How to use a digital multimeter
A digital multimeter is very easy to set up and use to run
tests in the lab. Simply follow the six steps below to set
up your digital multimeter and start measuring a device
under test (DUT).
1. Inspect your digital multimeter and DUT for signs of
2. Insert the appropriate probes into the DMM inputs
(the probes and inputs are typically color coded for ease
3. Set your DMM to resistance, voltage or current mode,
depending on what you’re measuring.
4. Test that your DMM is working correctly with
a known voltage source.
5. Hold the tip of the probes or clamps to the
positive and negative terminals of the DUT to
make your measurements.
6. As you’re working, watch the DMM’s display
screen for safety warnings.
DIGITAL STORAGE OSCILLOSCOPE
A digital storage oscilloscope (DSO) is an electronic test
instrument that is used to measure and display electrical
signals. Unlike traditional analog oscilloscopes that use a
CRT (cathode-ray tube) display, a DSO uses digital signal
processing to capture, store, and display waveforms on a
A DSO can capture and store waveforms in its memory,
allowing you to view and analyze them at a later time.
This makes it ideal for applications that require detailed
analysis of complex signals, such as digital
communication systems, power electronics, and control
Why are digital storage oscilloscopes
An oscilloscope measures and displays voltage signals on a
time-versus-voltage graph. In most applications the graph
shows how the signal changes over time: the vertical (Y) axis
represents voltage, and the horizontal (X) axis represents
• This simple graph can tell you many things about a signal:
• View the signal for anomalies
• Calculate the frequency of an oscillating signal
• Tell if a malfunctioning component is distorting the signal
• Tell how much of the signal is noise and whether the noise
is changing with time
How to use a digital storage
1. Connect the probe
2. Adjust the vertical scale
3. Adjust the horizontal scale
4. Adjust the trigger:
5. Capture the waveform
6. Analyze the waveform
7. Save and export data
Digital multimeter vs. oscilloscope
A digital multimeter allows you to read the voltage at any one moment in time,
but oscilloscopes show how the voltage changes over time by graphically displaying a
waveform. Oscilloscopes are often used over digital multimeters when
troubleshooting more complex circuits.
Used to: Circuit type:
Oscilloscope Circuit type:
Measure how the voltage
changes over time.
Read the voltage at any one
moment in time.