Operating Instructions
Making Measurements
All measurements are made by first setting the function knob to a specific
setting (the meter will select the default function for that position) and
then select a measurement using the menu keys. Note that not all func-
tion knob settings have a corresponding menu selection option.
For example, the steps below show how to take a DC voltage measurement.
1. Set the measurement knob to V for a voltage measurement.
NOTE:
The default for this range is AC voltage.
2. Select the menu key 2 change to DC voltage (Fig 1).
3. Connect the test leads to the correct input jacks (COM, V
Ω
, ,
, TEMP).
Voltage (mV, V) Measurements
Ranges available in volts functions are:
• mV
50.000mV, 500.00mV DC and 500.00mV AC
• V
5.0000V, 50.000V, 500.00V, 1000.0V
*dBm readout = 10 x log (primary display readout 2/r), where R = 600
Ω
(default)
db readout = 20 x log (primary display readout / ref), where ref = 1V (default)
This meter has high impedance circuitry (10M
Ω
) for measuring voltage.
AC Voltage Measurement
All push-button features are available in this function. The on screen
menu selection accesses decibel (dBm or dB) measurements.
dB (dBm or dB V) measurements in AC volts function.
The AC volts function allows you to display readings as deviations in dB
(decibels) above or below an established reference level.
Set up dB measurements by using the on screen menu selection buttons
when measuring AC volts. The dBm (or dB V) value appears in the
s e c o n d a ry display and the AC reading appears in the primary display.
Normally dB is measured as dBm, which is a measure of decibels relative
to 1 milliwatt. The meter assumes a resistance of 600
Ω
in making this
calculation. This resistance can be set for any value from 1
Ω
to 1, 9 9 9
Ω
by using the setup menu selection buttons. When measuring dB V, the
reference voltage can be set for any value from 0.1000V to 5.0000V by
using the setup menu.
DC Voltage Measurement
All push-button features are available for a standard DC voltage reading.
Both AC and DC voltage measurements.
When a DC volts function is selected, the meter can display the combined
AC+DC (RMS) value or AC and DC components of a signal separately by
using the on screen menu selections.
When the meter shows AC over DC (AC voltage in the primary and DC in
the secondary display), the other push-button functions except “
RA NGE
”
are not available.
A p p l i cations: Using AC+DC in AC/DC volts mode
To take the combined AC+DC total RMS volts measurement, press menu
key 4. In the above example the total RMS value of 6.118 V shows on the
primary display and the frequency of 60.00 Hz shows on the secondary
display. When calculating the power dissipated in a circuit component, it
is critical that the DC value is factored into the equation V
rms
x I
rms
where V
rms
is AC+DC total RMS.
DM397-MAN
P. 6
(Fig 1)
Measurement
DC millivolts
(default)
AC
Menu key
(no selection)
AC
Connect Le a d s
P r i m a ry Display
DC
AC
S e c o n d a ry Display
-
Hz
Measurement
True RMS AC
Voltage
(default)
DC Voltage
dBm
dB
AC+DC total
RMS
AC DC dual
display
Menu key
(no selection)
DC
dBm or dB
(press to tog-
gle
AC+Dc or
AC DC (press
to toggle)
Connect Le a d s
P r i m a ry Display
AC
DC
AC
DC
AC+DC
AC
S e c o n d a ry Display
Hz
-
dBm
dB
Hz
DC
dB = 20 x log (Vx ÷Vr )
• For dBm, Vr is the voltage across the reference resistance
at 1 milliwatt. For example, Vr would be 0.77 46 V with a
600 reference resistance.
• For dB V, the reference voltage is 1 V.
DC = 6 V
AC = 1.2 Vrm
Frequency = 60 Hz
