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NANO
DMR20-1-FM
Self-Powered,
LED Display, AC Line Frequency Monitor
FEATURES
Self-powered from 85 to 264Vac / 45-65Hz supplies
0.01Hz resolution & quartz crystal accuracy and
stability
Installs in “oiltight” 1.20 inch (30.5mm) round
cutouts
Four-digit LED display with out-of-range indication
Digital replacement for analog panel meters
Self-resetting internal fuse for long-term reliability
Supplied with EPDM rubber gasket and plastic hex nut
Provides moisture ingress protection to IP67/NEMA 6
Screw-style input terminal block simplifies installation
Knockout punches and tooling available
Approvals to UL/cUL/IEC/ 61010-1
Murata Power Solutions’ new DMR20-1-FM is the world’s smallest, self-powered, ac line
frequency monitor. Simply connect 85 to 264Vac (45-65Hz) power and the meter is fully
operational—no additional components are required. The unit can also measure distorted
120Vrms power sources with triangle and square waveforms, as well as quasi sine wave
outputs of dc to ac power inverters.
An ultra-stable, quartz-crystal controlled microprocessor provides accuracies of ±0.02Hz
over the operating temperature range of -25 to +60°C. DMR20-1-FM frequency moni-
tors feature a large, 0.30”/7.6mm, bright LED display that can be easily read from 10 feet
away (3 meters). A built-in resettable fuse and out-of-range indication assures long term
reliability.
The DMR20-1-FM is housed in a rugged, round polycarbonate case that provides excellent
protection against moisture, dust, shock and vibration. Panel installation is straightforward:
using available tooling, simply drill and punch a 1.2 inch (30.5mm) diameter hole and
anti-rotation notch, insert the meter and gasket, and securely fasten the meter using the
supplied hex nut. The nut and gasket are designed to provide moisture ingress protection to
IP67/NEMA 6.
DMR20-1-FM is exactly the same size as Murata Power Solutions’ DMR20-1-ACV (ac volts),
DMR20-10-DCM (dc volts), and DMR20-1-TMP (temperature) digital panel meters.
E156931
Performance/Functional Specifications
Typical at Ta = +25°C, Vin = 250Vac / 60Hz sine wave, unless
otherwise noted
AC Input (TB1)
Voltage Range
➀
Current Consumption
UL/IEC61010-1
Performance
Sampling Rate
Resolution
Accuracy @ +25°C
Temperature Drift
Mechanical
Dimensions
85 to 264Vac (45-65 Hz)
250Vac/60Hz: 12mA (max.)
Measurement Category II
2-3 readings/second
0.01Hz
±0.01Hz (typ.), ±0.02Hz (max.)
±0.0005Hz/°C (–25 to +60°C)
1.5" diameter x 1.1” depth
(38 x 28mm)
Display Type
Four digit, LED, 0.30” high (7.6mm)
Weight
0.9 ounces (25.5 grams)
Case Material
Polycarbonate
Terminal Block Torque
2.2 lb·in (0.25 N·m) ±20%
Wire Size And Type
18-22AWG (0.83-0.33mm
2
) copper,
solid or stranded
Wire Insulation Strip Length 0.25" (6.4mm)
Environmental
Operating Temperature
–25 to +60°C
Storage Temperature
–40 to +75°C
Humidity (non-condensing) 0 to 85%
➀
Operation and accuracy with ac inputs above or below this range are not specified.
Ordering Information
DMR20-1-FM-R-C
Knockout Punches
DMR20-1-KP
DMR20-2-KP
DMR20-3-KP
1.2" (30.5mm) Round knockout punch
(no keying notch)
1.2" (30.5mm) Round knockout punch
(with four keying notches)
1/8" and 3/16" (3.2 and 4.7mm)
key-notch nibbler tool
85 to 264Vac frequency monitor (Red LED)
Note: An M30 x 1.5 nylon hex nut and EPDM sealing gasket are supplied with each
meter. The “-C” suffix denotes RoHS compliance.
Operation from waveforms other than sine waves is limited to 120Vrms. See Technical
Note 1 for additional information.
For full details go to
www.murata-ps.com/rohs
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MPM_DMR20-1-FM.A02
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NANO
DMR20-1-FM
TECHNICAL NOTES
Self-Powered,
LED Display, AC Line Frequency Monitor
Panel Materials:
Acceptable panel materials include aluminum, mild steels, plastics,
FR-4 pc-board (fiberglass), and many other materials with a flat matte
surface on both sides of the cutout. The DMR-20-x-KP tools can be
used with most panel materials except stainless steel or other hard-
ened metals.
DMR20-1-FM has passed vibration testing combined with temperature
cycling while mounted to the materials noted above, using the specified
tightening torques. If the meter will be mounted to extremely smooth,
slippery surfaces, the user is advised to test the completed assembly
under the environmental conditions encountered in the end application.
5. AC Input Fusing and Wiring:
DMR20-1-FM frequency monitors
contain an internal, self-resettable fuse. However, the supply wires
connected to input terminals TB1-A and TB1-B must be fused with an
external, user supplied, 0.25A/300V time delay/time lag fuse, in accor-
dance with applicable regulatory codes.
All supply wiring must be rated for the voltages and currents they will
conduct and comply with any code or application-mandated require-
ments pertaining to the user’s specific installation. 300V, UL-rated
hook-up wire suitable for the intended application is required. TB1 is to
be used only for powering the meter’s internal circuitry; it must not be
used to supply power to external loads.
The recommended TB1 supply wire size is 18AWG to 22AWG (0.83mm
2
to 0.33mm
2
) solid or stranded copper wire. The supply wires must be
properly stripped and attached to TB1 such that their insulation is not
pinched by the screw terminal. Recommended insulation strip length is
0.25” (6.4mm). When using stranded wire, verify that there are no loose
or stray strands that could potentially cause a short circuit across the
ac supply input.
6. AC Input Polarity and Grounding:
The ac supply inputs TB1-A and
TB1-B terminals are not polarity sensitive, that is, neither terminal is
designated as “AC LO” or “AC HI.” DMR20-1-FM frequency monitors do
not include, nor require, a connection to earth/chassis ground.
!
IMPORTANT! To ensure safe and reliable operation, DMR20-1-FM ac
frequency monitors must be installed and serviced by qualified
technical personnel. Contact Murata Power Solutions if there is
any doubt regarding their installation or operation.
1. Measurement Type:
DMR20-1-FM meters are designed to be powered
from sine wave ac supplies, over their rated input of 85-264Vac (45-
65Hz). Operation from triangle, square, and quasi-sine waveforms is
limited to a maximum of 85 to 120rms (45-65Hz).
2. Calibration:
DMR20-1-FM frequency monitors are factory calibrated;
there are no provisions for calibrating these meters in the field.
3. Operating Range:
As the sine wave ac input voltage is lowered below
100Vac (50 or 60Hz), the DMR20-1-FM’s display may begin to dim
slightly, but the readings will remain accurate down to 85Vac. Input
frequencies below 45Hz and above 65Hz will display as four dashes,
indicating an out-of-range input condition.
4. Panel Installation:
All electrical connections to DMR20-1-FM must
be made after the meter is securely attached to the panel, and with
the input ac supply de-energized (off). In high-vibration environments,
adequate strain reliefs must be used on all supply wiring. See Figure 1
for typical panel mounting details.
Tightening Torque:
The recommended tightening torque for the M30 x 1.5 plastic hex nut
is 10 to 17 in-lbs (1.3 to 1.9 N-m). If a torque wrench is not available,
this recommended range can be approximated by hand tightening the
hex nut SLOWLY until it just bottoms out against the panel’s rear sur-
face. From this bottomed-out reference position, using a suitable tool,
tightening the hex nut ¼ turn clockwise will produce approximately 10
in-lbs (1.3 N-m) of torque; tightening it 3/8 turn clockwise will produce
approximately 17 in-lbs (1.9 N-m).
Check to make sure the housing’s anti-rotation key is aligned with the
notches on both the panel and the gasket before tightening the hex
nut. Over tightening the hex nut will distort the rubber gasket and may
damage the threads on both the nut and the housing, thereby compro-
mising the installation’s mechanical integrity and its ability to protect
against environmental effects.
Panel Thickness:
When using both the factory supplied EPDM gasket and hex nut (the
recommended standard installation method), the DMR20-1-FM can be
mounted in panels ranging from 0.032” to 0.250” (0.8 to 6.4mm) thick.
When the gasket is not used, the panel thickness range is 0.075” to
0.325” (1.9 to 8.3mm). However, using the factory supplied hardware
and tightening torque recommendations provides optimal resistance to
vibration, dust, and moisture ingress.
Figure 1. Panel Installation
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MPM_DMR20-1-FM.A02
Page 2 of 3
NANO
DMR20-1-FM
Self-Powered,
LED Display, AC Line Frequency Monitor
MECHANICAL SPECIFICATIONS
1.08 (27.4)
0.55 (14)
1.50 (38.1)
0.080 (2.03)
0.10 (2.5)
1.18 (29.8)
0.655 (16.64)
FREQUENCY
Hz
A B
TB1
Dimensions are in inches (mm).
Tolerances (unless otherwise specified):
.XX ± 0.02 (0.51)
.XXX ± 0.010 (0.254)
Angles ± 2˚
Components are shown for reference only.
3D models are available at www.murata-ps.com/en/3d/meters.html
0.100 (2.54)
0.062 (1.58)
1.210 (30.73)
Recommended panel cutout
1. Description of safety marks:
Caution, risk of electrical shock
Caution, risk of danger
Equipment is partially protected by double or reinforced insulation
Murata Power Solutions, Inc.
11 Cabot Boulevard, Mansfield, MA 02048-1151 U.S.A.
ISO 9001 and 14001 REGISTERED
2. Cleaning Instructions: Gently clean with dry cloth only.
3. Caution: if the equipment is used in a manner not specified by Murata
Power Solutions, the protection provided by the equipment may be
impaired.
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.
© 2016 Murata Power Solutions, Inc.
www.murata-ps.com/support
MPM_DMR20-1-FM.A02
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