DMR35-DCA Series
Precision DC Shunt Ammeter
PRODUCT OVERVIEW
The DMR35-DCA series of panel meter performs precision measurements of DC current and is
available in two models offering ranges from 1A to 25A . The 3-1/2 digit numeric display supports
precision measurement, and a fast-responding 21 segment bargraph tracks quickly-changing
measured values.
The internal precision shunt resistors simplify the meter’s use and allow for increased accuracy
compared with solutions relying on external shunt resistors. Rear-accessible DIP switches are
provided for the selection of measurement range and display brightness.
The meter is powered from an external 9-32VDC power supply and typically requires only 37 mA
when operated at 12V. The measurement inputs provide +/-48V of common-mode input range,
simplifying the meter’s use in a wide range of applications.
Features
Bright, easily readable LED display
Up to 3-1/2 digit measurements
Bar-graph display scale
0.8 % measurement accuracy
Precision internal shunt resistor
Selectable current measurement ranges
Unipolar/ Bipolar measurement options
User-adjustable display brightness
Mechanical drop-in replacement for
common analog-movement meters
Operates from 9 to 32 VDC
Low current consumption, 37 mA typical
at 12VDC
RoHS Compliant
Two year warranty
The DMR35 family features a rugged polycarbonate housing that is mountable in a round hole using
supplied screws, and is designed as a mechanical drop-in replacement for many commonly
available analog movement meters, making it ideal for use in laboratory instrumentation, factory
automation, and other applications requiring precise DC current monitoring
ORDERING INFORMATION:
MODEL NUMBER
DESCRIPTION
DMR35-DCA1-DC1-R
DMR35-DCA2-DC1-R
DC Ammeter, 1-5A ranges, 9-32VDC powered, red display
DC Ammeter, 10-25A ranges, 9-32VDC powered, red display
SIMPLIFIED BLOCK DIAGRAM
For full details go to
www.murata-ps.com/rohs
www.murata-ps.com
DMR35-DCA.A01.D04 Page 1 of 8
DMR35-DCA Series
Precision DC Shunt Ammeter
SPECIFICATIONS:
Measurement Performance
Measurement Ranges
DMR35-DCA1
DMR35-DCA2
Accuracy (25 °C)
Min
Typ.
Max
Units
0-1, 0-2, 0-3, 0-5, ±1, ±2, ±3, ±5
0-10, 0-15, 0-20, 0-25, ±10, ±15, ±20, ±25
0.8% of reading + 2
counts
0.01
A
A
Temperature Stability
% F.S. /°C
Burden voltage at highest range, full-scale input current (1)
DMR35-DCA1 (5 A)
50
mV
DMR35-DCA2 (25 A)
50
mV
Absolute Maximum Input Current (+I_IN to –I_IN, applied for 1 minute max. ) (2)
DMR35-DCA1
-10
10
A
DMR35-DCA2
-27
27
A
Absolute Maximum voltage differential (either +I_IN
-48
+48
V
or –I_IN to –VS) (2)
Notes:
1) ‘Burden Voltage’ is the voltage drop across the meter when measuring a current. Burden voltage is specified for a given input current – In this
case the maximum rated current at the highest measurement range.
2) Exceeding Absolute Maximum ratings may result in permanent damage to the meter.
Power Supply Characteristics
Operating Supply Voltage
Absolute Maximum Supply Voltage
Operating Supply Current
12V supply
24V supply
Display & User Interface
Display Type & Size
Min
9
-1
Typ.
Max
32
34
Units
V
V
37
25
3-1/2 digit 7-segment, 11.4mm (0.45 in.) high
21 segment curved bar-graph
Red (625nm)
Automatic
Flashing display
Dipswitch selectable (8 ranges)
Dipswitch selectable (4 ranges)
Small Terminals
14-24 AWG
6mm (0.24 in.)
0.4 N-m (3.5 lb.-in)
Display Color
Decimal Point Selection
Out-of-range Indication
Measurement Range Selection
Display Intensity Control
Terminal Blocks
Wire Size
Insulation Strip Length
Screw Tightening Torque
Mechanical/Environmental
Parameter
Operating Temperature
Storage Temperature
Humidity (non-condensing)
Sealing (front face, when installed with included gasket)
Mounting screws (4 included)
Screw Tightening Torque
Panel thickness when used with included mounting screws
Dimensions
Weight
DCA1
DCA2
Min
0
-40
0
Typ.
mA
mA
Large Terminals (-DCA2 only)
10-24 AWG
10mm (0.39 in.)
1.13N-m (10 lb.-in)
Max
50
70
85
Units
°C
°C
%RH
Splash and dust resistant
#4-20 0.5” thread forming
9 in-lb (1 N-m)
0.062 in. (1.6mm)
0.25 in. (6.3mm)
See Mechanical specifications for details
2.3 (65)
2.7 (77)
oz. (g)
www.murata-ps.com
DMR35-DCA.A01.D04 Page 2 of 8
DMR35-DCA Series
Precision DC Shunt Ammeter
OPERATION:
Measurement Type and Capabilities
The DMR35 series of digital ammeters employ a precision ADC and a low-power microcontroller to measure DC current. These meters provide full-scale
measurement ranges spanning 1 ampere to 25 amperes with extremely low burden voltages. These meters measurement systems supports a commonmode input voltage range of up to +/-48V with respect to the power supply return (-VS connection), simplifying high-side, low-side, and negative rail
current measurements.
FRONT PANEL & FRONT PANEL LAYOUT AND FUNCTION
Bar-graph Display: The 21 segment bar-graph display responds quickly and smoothly like an
analog meter movement to aid in reading rapidly changing measurements.
Numeric Display: The 3-1/2 digit display provides precise measurements for steady-state and
slowly changing measurement values.
REAR PANEL LAYOUT AND SCREW TERMINAL CONNECTIONS
Four screw terminals are provided for power and measurement connections, as well as a 5-position DIP switch for meter configuration, as described
below.
Rear Layout
Terminal #
Name
Function
1
+VS
Power supply input terminals (9-32 VDC)
DM35-DCA1
2
-VS
3
+I_IN
Current measurement input terminals
4
-I_IN
DIP Switch: Five individual switches support display intensity settings (SW1-SW2) and
measurement range selection (SW3-SW5)
DMR35-DCA2
Note: It is important to tighten all screw-terminals to their torque specifications. Proper
tightening will help ensure reliable operation. Applications subject to vibration should use
stranded wire.
(large terminal block for 25A)
POWER SUPPLY CONNECTIONS
The meter is powered through the +VS and –VS terminals and requires a DC power supply which may range from 9VDC to 32VDC. This supply is
electrically isolated from the meter’s measurement electronics, so that the meter’s measurement input terminals (+I_IN, -I_IN) do not need to be
connected to the meter’s power return terminal (-VS), and may vary as much as +/-48V from this connection. Please note that the meter’s isolation
barrier is intended only to simplify measurements, and not for safety purposes – the maximum voltage between the power supply terminals (+VS or –
VS) and the measurement input terminals (+I_IN, -I_IN) must be limited to +/-48VDC. The DMR35 series of meters incorporates protection against
momentary applications of both overvoltage and reverse polarity to the power supply(+VS, -VS) terminals. Depending on regulatory and application
requirements it may also be necessary for the user to add external fusing.
MEASUREMENT INPUTS
Current to be measured by the DMR35 is passed through the +I_IN and –I_IN terminals. This requires that the meter be inserted in the line in which
the current is to be measured. Unlike many panel meters, the DMR35 series’ measurement inputs are electrically isolated from the power supply
terminals, which allows for fully differential measurements over a common-mode range of +/-48V with respect to the power supply terminals +VS or VS.
www.murata-ps.com
DMR35-DCA.A01.D04 Page 3 of 8
DMR35-DCA Series
Precision DC Shunt Ammeter
CONNECTION EXAMPLES
The schematic below shows how a DMR35 DC current meter can be used to perform a ‘high-side’ current measurement, where the meter is inserted into
the load’s positive leg. In this example, the meter is powered from the same power source powering the load, and the meter’s current sensing terminals
(+I_IN, -I_IN) are at a potential of 12 volts higher than the meter’s negative power terminal (-VS). The meter can also just as easily be used to measure
current in the load’s negative leg (‘low-side’ current sensing).
It is also possible to use the meter to monitor voltage in a circuit that is independent of the meter’s power supply circuit, as shown in the schematic below.
When used in this way, the meter’s current measuring terminals may electrically float with respect to its power supply terminals, as long as the voltage
difference between the two terminal pairs remains within +/- 48V of each other.
www.murata-ps.com
DMR35-DCA.A01.D04 Page 4 of 8
DMR35-DCA Series
Precision DC Shunt Ammeter
METER CONFIGURATION
Meter Range Settings
DMR35 meter configuration is controlled through a 5-position DIP switch (SW1-SW5) on the rear of the meter. The individual switches are labelled 1
through 5 on the unit, and the ON position of the switches is also labelled. These switches are used to select both the meter’s measurement range
and the display intensity (brightness).
Switches SW3 through SW5 select the meter’s measurement range, as shown in the table below. Note that for these five meter models, switch SW3
selects either unipolar (OFF) or bipolar (ON) measurement ranges. Switches SW4 and SW5 select the magnitude of the measurement range.
SW3
Switch Setting
SW4 SW5
DIP switch
DMR35 Model
-DCA1
-DCA2
OFF
OFF
OFF
0-1 A
0-10 A
OFF
OFF
ON
0-2 A
0-15 A
OFF
ON
OFF
0-3 A
0-20 A
OFF
ON
ON
0-5 A
0-25 A
ON
OFF
OFF
±1 A
±10 A
ON
OFF
ON
±2 A
±15 A
ON
ON
OFF
±3 A
±20 A
ON
ON
ON
±5 A
±25 A
The meter behaves differently depending on whether bipolar or unipolar
range setting is selected. When the meter is set to a bipolar range
setting, it will display measurements over a +/- range, flashing the
display to indicate overflow for input values greater than +RANGE, and
flashing the display to indicate underflow for input values less than –
RANGE. A zero-value measurement will illuminate a single center LED.
Increasingly negative input values will illuminate the bargraph from
center to the leftmost LED until all left-side LEDs are illuminated at
negative full-scale, and increasingly positive input values will illuminate
the bargraph from center to the rightmost LED until all right-side LEDs
are illuminated at positive fullscale.
When set to a unipolar range setting, the meter will display
measurements over a positive only range. Negative input values will
result in an underflow condition of a flashing zero reading. Positive
input values exceeding the maximum range will result in a flashing
overflow condition. The bargraph will indicate a measurement of zero
or less by illuminating the leftmost LED, and increasingly positive input
values will illuminate the bargraph to the rightmost LED until all LEDs
are illuminated at positive fullscale.
The DMR35 meter family provides the ability to adjust the display
intensity to maximize readability over a range of ambient lighting
conditions. Switches SW1 and SW2 select the display intensity, as
shown in the table below. The meter provides for four settings (LOW,
MEDIUM, HIGH, and HIGH+). Note that the HIGH2 setting results in only
a slightly higher brightness than the HIGH setting.
Display Intensity Settings
Set the display intensity by setting the switches as shown:
3
SW1
SW2
Dipswitch
Display Intensity
OFF
OFF
Low
OFF
ON
Medium
ON
OFF
High
ON
ON
High2 †3
Provides only slightly higher intensity than ‘High’ setting
www.murata-ps.com
DMR35-DCA.A01.D04 Page 5 of 8
DMR35-DCA Series
Precision DC Shunt Ammeter
TECHNICAL NOTES
1.
Calibration
The DMR35 is calibrated at the factory at manufacture. There are no user or field-adjustable calibration features.
2.
Wiring
Power supply and input wiring must be rated for the electrical and environmental conditions under which the meter will be operated. They must
also comply with any regulatory or application-mandated requirements pertaining to the user’s installation. The terminal blocks can
accommodate wire gauges ranging from #14 to #24 AWG (#10-#24 for the large terminal blocks used on the DMR35-DCA2). Wiring Insulation
should be stripped to the proper length as described in Terminal Block specifications table and wires must be inserted into the terminal block
openings such that the screw terminal does not pinch any insulation. It is important to tighten all screw-terminals to their torque specification,
which also may be found in the Terminal Block specifications table. Proper tightening will help ensure reliable operation. Applications subject to
vibration should use stranded wire. After final assembly, inspect all terminal block connections for shorts between adjacent conductors; this
step is especially important when using stranded wire.
3.
Protection and Fusing
DMR35 meters’ power supply leads (+VS, -VS) are protected against momentary overvoltage and reverse polarity conditions. Input terminals
+I_IN and –I_IN are protected against noise and brief transients. Protection, however, is not provided against sustained conditions exceeding
the limits listed in in the Performance & Functional Specifications Table. External fusing must be supplied by the user in accordance to
applicable safety and regulatory requirements for the system in which the DMR35 is installed.
4.
Noisy Power Supplies
Some power supplies contain high-frequency switching devices that may conduct and/or radiate significant noise onto the low-level signal
developed across the measurement inputs. Even though the DMR35 incorporates built-in input filtering, some portion of this noise may be
amplified and subsequently measured by its sensitive input circuitry. Limiting runs of wire to less than 3 meters (10 feet) is strongly
recommended. Also, in systems with noisy power supplies, connecting an external, non-polarized capacitor across the +VS and -VS inputs can
help reduce measurement errors. In certain situations, the use of twisted pair or shield wiring may be required.
5.
Self-Diagnostics
On power-on the meter performs a self-test and checks the integrity of calibration data stored in internal non-volatile memory. If the factory
calibration data has been corrupted, the meter will display ‘CAL’ on power-on and approximately once a minute thereafter to indicate that the
meter is relying on default calibration factors and that displayed measurements may have more than the datasheet-specified amount of error. If
the meter detects other internal fault conditions, it will attempt to reset itself. Repeated restarts, which appear in the form of a highly
intermittent display, are indicative of a hardware fault that cannot be cleared through a reset operation, in which case the meter should no
longer be used.
www.murata-ps.com
DMR35-DCA.A01.D04 Page 6 of 8
DMR35-DCA Series
Precision DC Shunt Ammeter
PANEL INSTALLATION
Panel Drill Template
MECHANICAL SPECIFICATIONS
DMR35-DCA1-DC1-R
Panel Mounting
DMR35-DCA2-DC1-R
www.murata-ps.com
DMR35-DCA.A01.D04 Page 7 of 8
DMR35-DCA Series
Precision DC Shunt Ammeter
STANDARD PACKAGING
Murata Power Solutions, Inc.
129 Flanders Rd. Westborough, Ma 01581, USA.
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: https://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.
©2021 Murata Power Solutions, Inc..
www.murata-ps.com
DMR35-DCA.A01.D04 Page 8 of 8
