www.murata-ps.com
DMS-20RM Series
True-rms ac Voltmeters with Isolated Inputs
FEATURES
Measures the rms value of complex ac voltages
Three input ranges: 20Vac, 200Vac and 300Vac
operating-supply options: 85-264Vac, or +10-40Vdc
Two
circuit fully isolated from operating power supply
Input
47-1kHz input frequency range
encapsulated plastic package measures 1.38” x
Fully
0.88” (35mm x 22.4mm)
Large, easy-to-read, red LED display is visible from 12
feet (4m)
Murata Power Solutions’ DMS-20RM series are four-wire, self-contained ac voltmeters
that measure and display the true-rms values of complex ac waveforms. Because the input
circuitry is electrically isolated from the unit’s operating power source, these voltmeters
can measure signals down to zero volts. No external isolation transformers or auxiliary
power supply conditioning components are required. Simply connect the input signal and a
source of operating power (85-264Vac, or an optional +10-40Vdc) to the two rear-mounted
terminal blocks and the unit is fully operational.
DMS-20RM rms voltmeters are available in a choice of three input ranges: 20Vac
(with 0.01V resolution); 200Vac (0.1V resolution); and 0-300Vac (1V resolution). An input
frequency range of 47-1kHz makes these voltmeters ideal for all ac voltage monitoring
applications. And, unlike conventional, average-responding products, these meters can
measure and accurately display the true-rms value of triangle waves, square waves, or
other irregularly shaped waveforms with 0.4% full-scale accuracy.
The large (0.37”/9.4mm), bright red LED display makes the DMS-20RM ac voltmeters
easily readable from as far as 12 feet (4 meters). All units are packaged in a red-filter case
with a built-in bezel; these meters are fully encapsulated to make them moisture and vibra-
tion resistant. Their miniature size is perfect for high-end consumer electronics, laboratory
instrumentation, alternative power generators and other products requiring precise ac line
monitoring.
TYPICAL WIRING DIAGRAMS
FUSED
AC POWER
SUPPLY
A
TB1
FUSED
AC POWER
SUPPLY
FUSED
+
10-40Vdc
- DC POWER
SUPPLY
TB1
B
TB1
A
B
A
B
TB2
TB2
TB2
Figure 1B.
Powered by and measuring the same AC power source.
AC VOLTAGE
TO BE MEASURED
AC VOLTAGE
TO BE MEASURED
Figure 1A.
Powered by AC supply while measuring separate AC signal.
Figure 2.
Powered by DC power supply while measuring AC signal.
For full details go to
www.murata-ps.com/rohs
www.murata-ps.com/support
MPM_DMS-20RM.B01
Page 1 of 4
DMS-20RM Series
True-rms ac Voltmeters with Isolated Inputs
Performance/Functional Specifications
Typical at TA=+ 25ºC with 60Hz sine-wave input, unless otherwise noted
Full-Scale Input Voltage (TB2)
DMS-20RM-1
DMS-20RM-2
DMS-20RM-3
Frequency Range
Performance
Sampling Rate
Accuracy
➀
Measurement Type
Temperature Drift (0 to 60ºC)
Zero-Volt Reading (within 30 sec.)
Breakdown Voltage, TB1 to TB2
Input Impedance
DMS-20RM-1
DMS-20RM-2
DMS-20RM-3
Power Supply Voltage (TB1)
DMS-20RM-X-AC1
DMS-20RM-X-DC2
Power Supply Current (TB1,
➁)
DMS-20RM-X-AC1
DMS-20RM-X-DC2
Terminal Block Wiring (TB1 and TB2)
Wire Size
Insulation Strip Length
Screw Tightening Torque
Rated Voltage
Display
Display Type and Size
Overrange Indication
Decimal Point
Physical/Environmental
Operating Temperature
Storage Temperature
Humidity (non-condensing)
Dimensions
Weight:
-25
-40
0
—
—
—
+60
+75
85
ºC
ºC
%
3½ Digit LED, 0.37”/9.4mm high
“1___”
Fixed, model dependent (see full-scale input
voltage above)
16-22AWG, Solid or stranded
0.250 inches
2.2 lb·in (0.25 N·m) ±20%
300Vac
—
—
30
10
50
15
mA/47-63Hz
mAdc
85
+10.0
—
—
264
+40.0
Vac/47-63Hz
Vdc
—
—
—
20
200
266
—
—
—
kΩ
kΩ
kΩ
-001
2000
2.5 reading per second
±0.4%FS ±2 counts
with 60Hz sine wave input
rms responding, Crest Factors of 1-5
±0.2
000
—
±0.4
001
—
Counts/ºC
Counts
Vdc
Min.
0
0
0
47
Typ.
—
—
—
60
Max.
19.99
199.9
300
1000
Units
Vac
Vac
Vac
Hz
ORDERING INFORMATION
DMS-20RM-1-AC1-R-C
DMS-20RM-2-AC1-R-C
DMS-20RM-3-AC1-R-C
DMS-20RM-1-DC2-R-C
DMS-20RM-2-DC2-R-C
DMS-20RM-3-DC2-R-C
0 to 19.99Vac, AC Powered
0 to 199.9Vac, AC Powered
0 to 300Vac, AC Powered
0 to 19.99Vac, DC Powered
0 to 199.9Vac, DC Powered
0 to 300Vac, DC Powered
A DMS-BZL4-C bezel assembly with sealing gasket is supplied with each meter.
See
www.murata-ps.com/dpm-availability
for model-specific availability.
IMPORTANT!
To ensure safe and reliable operation, DMS-20RM ac
voltmeters must be installed and serviced by qualified technical personnel.
Contact Murata Power Solutions if there is any doubt regarding installation
and/or operation.
TECHNICAL NOTES
1. Measurement Type:
DMS-20RM series ac voltmeters employ a preci-
sion rms-to-dc converter and a high-precision voltage reference to
measure and display the rms value of complex ac waveforms. Please
note, the rear-mounted potential transformer is used to isolate the
input signal being measured (TB2) from the ammeter’s operating power
source connected to TB1. Do not pass any conductors through this
transformer’s center hole as this will introduce significant measure-
ment errors.
2. Wiring:
All power supply and input signal wiring must be rated for the
voltages and currents they will carry and must comply with any code
or application-mandated requirements pertaining to the user’s specific
installation.
3. Power Supply Polarity, Fusing, and Grounding:
As shown in Figures
1A, 1B, and 2, the two power supply inputs, TB1-A and TB1-B, on
ac-powered DMS-20RM voltmeters (“-AC1” suffix) are not polarity
sensitive, that is, they have no “AC LO” or “AC HI” designations. Also,
ac-powered models do not include or require a connection to earth/
chassis ground. DC-powered models (“-DC2” suffix) are reverse-polarity
protected, and must be connected as shown in Figure 2 for proper
operation.
DMS-20RM voltmeters are not internally fused. Terminal block TB1 is to
be used only for powering the power meter’s internal circuitry; it must
not be used to supply power to external loads. The supply wires feeding
these power meters must be fused with a 0.25A/250V time delay/time
lag fuse, in accordance with applicable regulatory codes.
Wire insulation must be stripped to within ±10% of the stated dimen-
sions, and wires should be inserted into TB1 such that their insulation
is not pinched by the screw terminal. See the Functional Specifications
section of this data sheet for wire sizes and tightening torque for TB1’s
screw terminals.
4. Calibration:
Periodic recalibration of DMS-20RM voltmeters is not
required under normal, indoor operating environments. If calibration is
necessary, it should only be performed by qualified technical personnel.
Calibration is performed with potentially lethal voltages applied to the
DMS-20RM and its associated wiring. A plastic, fully-insulated adjust-
ing tool must be used to access the recessed calibration potentiometer
located on the back of the unit (see Mechanical Specifications). Contact
Murata Power Solutions if additional information is required regarding
calibration, setup, or any other technical issue pertaining to DMS-20RM
ac voltmeters.
Model dependent; see product datasheet.
1.3 Ounces (36 grams) nominal
➀
Specified accuracy applies to inputs with crest factors (CF) up to 2.0, where CF = Vpeak/Vrms.
Crest factors of 2 to 5 introduce an additional error of ±3% of full scale. Voltmeters are calibrated
with a near full-scale, 60Hz sine-wave input.
➁
Specified maximum power supply currents are steady state; larger surge currents can occur at
initial application of power.
www.murata-ps.com/support
MPM_DMS-20RM.B01
Page 2 of 4
DMS-20RM Series
True-rms ac Voltmeters with Isolated Inputs
Panel Installation
All connections to DMS-20RM ac voltmeters must be made after the meter
is securely attached to the panel, with all associated ac supply power
sources de-energized (off). The installed wire positions should be such that
minimal forces are applied to terminal blocks TB1 and TB2. In high-vibration
environments, proper strain reliefs must be used for all wiring.
To ensure a secure panel-mount installation, MPS recommends using the
DMS-BZL4-C bezel assembly (with sealing gasket) supplied with each DMS-
20RM voltmeter. See the ‘Mechanical Specifications’ section for detailed
cutout and voltmeter dimensions.
Following the four-step sequence shown in Figure 3 — being careful not to
apply excessive force or twisting motions — insert the DMS-20RM into the
panel opening. When using the DMS-BZL4-C, install its sealing gasket so it
is positioned between the voltmeter’s front flange and panel front surface
(see Mechanical Specifications). Be sure to use and securely tighten all four
screws supplied with the bezel assembly.
Step 1.
Step 2.
Step 3.
Step 4.
Figure 3. Panel Installation
Murata Power Solutions, Inc.
11 Cabot Boulevard, Mansfield, MA 02048-1151 U.S.A.
ISO 9001 and 14001 REGISTERED
This product is subject to the following operating requirements
and the Life and Safety Critical Application Sales Policy:
Refer to:
http://www.murata-ps.com/requirements/
Murata Power Solutions, Inc. makes no representation that the use of its products in the circuits described herein, or the use of other
technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein do not imply
the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifications are subject to change without
notice.
© 2015 Murata Power Solutions, Inc.
www.murata-ps.com/support
MPM_DMS-20RM.B01
Page 4 of 4
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