www.murata-ps.com
DCA-20PC Series
LED Display, Subminiature DC Ammeters with Built-In Shunts
FEATURES
Built-in shunts for digitally measuring dc currents
from 200uA to 20A
Functionally complete – no additional components
required
Wide power supply inputs:
5 to 40Vdc for 5V/12/24V/28V applications
36-75V option for telecom supplies
8-36Vdc Isolated-supply models for high-side shunts
20mV internal shunt minimizes power loss
Includes load connections for easy 3 or 4-wire
operation
High resolution; Factory calibrated to ±0.1% accuracy
Large, easy-to-read, LED display with 0.37” (9.4mm)
high digits
Available with red, blue or green LED displays
Small 1.38˝ x 0.88˝ x 1.0˝ package
Murata Power Solutions’ new DCA-20PC Series are the first digital dc ammeters to include built-in
shunts for measuring dc currents up to 20A. Six ranges provide for precision measurement of
dc currents from 200uA to 20A. These ammeters are 100% self-contained; no calibration or
user-supplied components are required—they even include terminal blocks for your external load
circuit, a feature that enables simple 3-wire operation!
Two shunt-configurations are offered: grounded-shunt (“low side”), 5-40V-powered models
for cost-sensitive applications, and 8-36V isolated-supply models for high side or floating shunt
applications. A versatile power supply design accommodates all popular supply voltages from 5 to
75Vdc. Reverse-polarity-protected supply inputs ensure trouble free installation. And, because many
dc ammeters are installed in battery backup applications, power consumption is typically below 1
Watt for 8-36V models, and below 75mW for 5-40V models. To further reduce overall power con-
sumption, the voltage dropped across its built-in series shunt is only 20mV!
DCA-20PC Series ammeters are housed in subminiature, 1.38˝ x 0.88˝ (35mm x 22mm),
rugged packages that feature a large, 0.37˝/9.4mm high, LED display. A built-in, high-contrast
color filter ensures that legibility is not compromised: the display can be easily read at distances
up to 15 feet (5 meters). Available LED-display colors include brilliant blue, bright green, and
standard red.
Built-in shunts, Precision electronics, miniature size, wide power supply inputs, low power
consumption, and no-hassle 3-wire installation make DCA-20PC Series the ideal choice for all
your 200uA to 20A ammeter-applications.
LED DISPLAY
–
INPUT
AMPLIFIER
+5V
A/D
CONVERTER
–5V
POWER
CONVERTER
+
BUILT-IN
SHUNT
*
SIGNAL
GROUND
1
1
2
2
2
3
TB2
POWER
GROUND
–
1
2
+
TB1
*
Open on isolated-supply models
**
Applies to isolated-supply models only
LOAD (+)
+V
–V
–SHUNT
(–V)
+SHUNT
**
–
EXTERNAL
LOAD
+
–
EXTERNAL
DC SUPPLY
+
For full details go to
www.murata-ps.com/rohs
Figure 1. Simplified Schematic
www.murata-ps.com/support
MPM_DCA-20PC.C01
Page 1 of 6
DCA-20PC Series
Performance/Functional Specifications
Typical at T
A
= +25°C, unless otherwise noted.
Full Scale Load Current
➀
DCA-20PC-1
DCA-20PC-2
DCA-20PC-3
DCA-20PC-4
DCA-20PC-5
DCA-20PC-6
Overcurrent Rating (<6 sec.)
➁
Internal Shunt Resistance
DCA-20PC-1
DCA-20PC-2
DCA-20PC-3
DCA-20PC-4
DCA-20PC-5
DCA-20PC-6
–
–
–
–
–
–
–
–
–
–
–
–
100
10
1.0
0.1
0.01
0.001
Ohms
Ohms
Ohm
Ohm
Ohm
Ohm
LED Color:
BL
= Low-Power Blue
BS
= Super Blue
GS
= Standard Green
PGL
= Low-Power Green
RL
= Low-Power Red
Min.
–
–
–
–
–
–
Typ.
–
–
–
–
–
–
Max.
199.9
1.999
19.99
199.9
1.999
19.99
Units
µAdc
mAdc
mAdc
mAdc
Adc
Adc
Physical/Environmental (continued)
Humidity (non-condensing)
Case Material
Dimensions
Weight
0
–
85
%
LED Display, Subminiature DC Ammeters with Built-In Shunts
Polycarbonate
1.38"W x 0.88" x 1.0" nominal
0.6 ounces (17 grams)
Ordering Information
1.5x rated full-scale load current
DCA-20PC - 1 - DC1 - R L - C
Add
-C
for RoHS
Shunt Input to Power Supply Isolation
➂
DCA-20PC-X-DC4
models only
Performance
Sampling Rate
Accuracy
Zero-Current Reading
➃
Temperature Drift
(0 = +60°C)
“–001”
–
2.5 reading per second
±0.15%FS
“000”
±0.2
“001”
±0.4
Counts
Cnts/°C
500
–
–
Volts
Input Range:
Full-scale load current
1
= 199.9µA
Power Supply:
2
= 1.999mA
DC1
= +5-40Vdc, non-isolated power
3
= 19.99mA
(available with -RL, -BL, or -PGL LEDs)
4
= 199.9mA
DC4
= +8-36Vdc, isolated power
5
= 1.999A
(available with -RL, -BS, or -GS LEDs)
6
= 19.99A
See
www.murata-ps.com/dpm-availability
for model-specific availability.
Accessories:
DMS-20-CP
Panel Cutout Punch
A
DMS-BZL4-C
bezel assembly with sealing gasket is
supplied with each ammeter.
➀
The noted full-scale values are the external load currents that the ammeter is
designed to measure. This current enters TB-1 (-SHUNT), passes through the am-
meter’s built-in shunt and exits via TB1-2 (+SHUNT). For all models, this same full-
scale load current can also be routed, if the user so chooses, through TB2-1 and
TB2-2 (connection to positive rail of power supply). See detailed wiring diagrams.
Measuring positive and negative currents (bipolar operation):
In applications
where both positive and negative currents must be measured, Murata Power Solu-
tions recommends using ‘-DC4’ 8-36V isolated supply models. Negative current
flow is denoted by the illumination of the display’s negative (-) sign; the absence
of a negative sign implies positive current flow. Contact MPS if you have any ques-
tions regarding bipolar operation of DCA-20PC ammeters.
➁
For all models, the application of 1.5 times the rated full-scale load current is
permissible as long as this overcurrent condition does not exceed 6 seconds and
occurs no more than once in a 60 second interval (10% duty cycle).
➂
Breakdown (isolation) voltage applies only to ‘-DC4’ isolated-power models. Break-
down voltage is tested with TB1-1 tied to TB1-2 (-SHUNT shorted to +SHUNT),
and TB2-1, TB2-2, and TB2-3 all tied together (+V shorted to -V). 500Vdc is then
applied between the two shorted terminal-block pairs; the maximum permissible
leakage current is 5uA.
➃
Zero reading is measured with TB1-1 (-SHUNT) shorted to TB1-2 (+SHUNT).
➄
The Operating power supply voltage is applied to TB2-1-2 (+V) and TB2-3 (-V)
on ‘-DC4’ models, and to TB1-1 (-SHUNT) and TB2-2 (+V) on ‘-DC1’ models. On
all models, TB2-1 and TB2-2 are internally tied together (+V). Operating supply
current is the current which powers the meter’s analog and digital circuits; it is
measured with zero load-current passing through the ammeter’s built-in shunt
(i.e., with the display reading “000” and one decimal point enabled).
On 5-40Vdc powered (‘-DC1’), grounded-shunt models, the ammeter’s operating
supply current enters TB1-1 (-Shunt) but is not included in the displayed reading
(i.e., it does not pass through the built-in shunt).
Operating Supply Voltage (TB2 Terminals 1, 2 and 3)
➄
DCA-20PC-X-DC1-XX
DCA-20PC-X-DC4-XX
+5.0
+8
–
–
+40
+36
Vdc
Vdc
Operating Supply Current (TB2 Terminals 1, 2 and 3)
➄
DCA-20PC-X-DC1-XX (@ 5-40V)
DCA-20PC-X-DC4-XX (@ 8V)
DCA-20PC-X-DC4-XX (@ 36V)
TB1 and TB2 Terminal Blocks
Wire Size
Insulation Strip Length
Screw Tightening Torque
Rated Current
12-20AWG, (solid)
14-20AWG, (stranded) copper wire
0.250 inches
4.4 pound/inches (0.5Nm)
20A with 12AWG solid copper wire;
15A with 14AWG solid or stranded
copper wire
–
–
–
10
100
25
15
150
40
mAdc
mAdc
mAdc
Display
Display Type and Size
Overrange Indication
Display Reading/Decimal Point
Physical/Environmental
Operating Temperature
Storage Temperature
0
–20
–
–
+60
+75
°C
°C
3½ digit, 0.37"/9.4mm high red, blue or
green LED
"–1_ _ _" for negative Vin
"1_ _ _" for positive Vin
Model dependent
www.murata-ps.com/support
MPM_DCA-20PC.C01
Page 2 of 6
DCA-20PC Series
LED Display, Subminiature DC Ammeters with Built-In Shunts
TECHNICAL NOTES
To ensure safe and reliable operation, DCA-20PC dc ammeters
must be installed and serviced by qualified technical personnel.
DC ammeter applications can expose a user to potentially lethal
currents and voltages. Power and load connections must be made
with all associated power sources de-energized. Contact Murata
Power Solutions if you have any questions regarding installation
or operation of any of our digital instruments.
1. Calibration:
DCA-20PC ammeters are factory calibrated using a high-
precision current source. Under normal indoor operating conditions,
periodic recalibration is not necessary. The calibration potentiometer,
located on the back of the ammeter, is a ¾ turn type; do not force its
adjustment screw past the two end stops. If recalibration is necessary,
it must be performed by qualified personnel. Calibration is performed
by applying a precision current source to TB1’s -SHUNT and +SHUNT
terminals. For best results, use a load current that is approximately
95% of the ammeter’s full-scale rating.
The calibration current source and power supply inputs must be con-
nected per the appropriate model-specific wiring diagram shown later
in this data sheet. Using an insulated slotted tool, adjust the calibra-
tion potentiometer until the display is within ±1 count of the desired
reading. Please note, the potentiometer provides an adjustment range
of approximately ±1%. Contact Murata Power Solutions if additional
information is required regarding calibration or setup of DCA-20PC
ammeters.
2. Wiring and Fusing:
Power supply (TB2) and input (TB1) wiring must be
rated for the electrical and environmental conditions under which the
ammeters will be operated. They must also comply with any regula-
tory or application-mandated requirements pertaining to the user’s
installation. Connections to DCA-20PC ammeters must be made with
all power sources de-energized. Refer to the Functional Specifications
section for detailed wire type and wire gauge information.
DCA-20PC-X-DC1-XX
1
DCA-20PC ammeters’ power supply and shunt terminals are not
internally fused. Therefore, the supply wires connected to both the
meter and the load must be fused according to the maximum current
rating (or lower) of the wire gauge used, in accordance with applicable
regulatory codes.
Wiring Insulation should be stripped to within +/-10% of the stated
dimensions. All wires must be inserted into the terminal block openings
such that the screw terminal does not pinch any insulation. After final
assembly, inspect all terminal block connections for shorts between
adjacent conductors; this step is particularly important when using
stranded wire.
3. Terminal Block Torque Ratings and Wire Size:
It is important to
tighten all TB1 and TB2 screw-terminals to their torque specification
of 4.4 pound-inches (0.5Nm). Proper tightening will minimize thermal/
electrical losses and ensure reliable operation. Under severe operation
conditions (for example, vibration, high continuous load currents, and
wide variations in ambient temperature), 25% over-tightening is permis-
sible. Applications subject to vibration should use stranded wire.
Proper terminal block torque is extremely important on all 20A models
(DCA-20PC-6 part numbers). Loose connections can overheat, thereby
posing a potential fire hazard to the terminal blocks, the load and
supply wiring, the ammeters themselves, and nearby equipment. 20A
models must use either 14AWG stranded or 12 AWG solid copper
wires only. However, in some applications, regulations can limit the
continuous current flowing in 14AWG solid or stranded copper wire to
15A maximum.
4. High-Side versus Low-Side Shunts:
Incorrect shunt connections
are one of the most common problems encountered when applying
digital dc-ammeters. Incorrect shunt connections can cause permanent
damage to the ammeter and its associated equipment.
DCA-20PC-X-DC1-XX
1
DCA-20PC-X-DC1-XX
J3 MUST BE
INSTALLED
(FACTORY
SETTING
FOR 5-40Vdc
SUPPLIES)
J3 MUST BE
INSTALLED
(FACTORY
SETTING
FOR 5-40Vdc
SUPPLIES)
1
J3
CAL
1
2
J3
CAL
1
2
CAL
J3
1
2
REMOVE J3
FOR 36-75Vdc
SUPPLIES
SHUNT
MUST BE
IN LOW
SIDE
–SHUNT
(–V)
1
TB1
2
1
TB2
2
1
TB2-1 & TB2-2
INTERNALLY
SHORTED
+SHUNT
SHUNT
MUST BE
IN LOW
SIDE
–SHUNT
(–V)
TB1
2
1
TB2
2
TB2-1 & TB2-2
INTERNALLY
SHORTED
SHUNT
MUST BE
IN LOW
SIDE
1
TB1
2
1
TB2
2
TB2-1 & TB2-2
INTERNALLY
SHORTED
+V
+V
+SHUNT
+V
–SHUNT
(–V)
+SHUNT
+V
+V
–
LOAD
+
–
LOAD
+
–
LOAD
+
LOAD CURRENT
LOAD CURRENT
LOAD CURRENT
–
–
DC SUPPLY
5-40Vdc
+
–
DC SUPPLY #2
(For Load Only)
+
–
+
DC SUPPLY
36-75Vdc
+
DC SUPPLY #1
5-40Vdc
Figure 2A. Low-Side Shunt Connections for "-DC1"
5-40Vdc Non-Isolated Supply Models
Figure 2B. Low-Side Shunt Connections for "-DC1"
Models using Two Power Supplies
Figure 3. Low-Side Shunt Connections for "-DC1"
Models Modified for 36-75Vdc Non-Isolated Power
(See Technical Note 6)
www.murata-ps.com/support
MPM_DCA-20PC.C01
Page 3 of 6
DCA-20PC Series
LED Display, Subminiature DC Ammeters with Built-In Shunts
TECHNICAL NOTES
Low-side shunts:
Applications that employ a single power supply to
power both the load and the ammeter, and the external shunt is located
in the negative side of the supply (commonly referred to as “low side” or
“grounded shunt”) should use ‘-DC1’ non-isolated power DCA-20PC Series
ammeters. Figures 2 and 3 depict typical low-side shunt connections.
High-side shunts:
‘-DC4’ 8-36Vdc isolated-power models must be
used in all applications that employ a single power supply to power
both the load and the ammeter and the shunt is located in the high side
(positive terminal) of the power supply. Figures 4 and 5 depict typical
high-side shunt connections. As shown in Figure 5, ‘-DC4’ isolated-
power models can also be used in applications where one supply
powers the ammeter and a second supply powers the load, but the two
supply-grounds cannot be tied together. ‘-DC4’ models include a built-in
dc/dc converter to provide a minimum 500Vdc isolation between the
shunt (TB1) and power supply (TB2) inputs.
5. Replacing Analog Panel Meters:
DCA-20PC ammeters can be used
as replacements for analog panel meters if a suitable dc voltage
is available for powering the ammeter. In retrofit applications, it is
important to determine the shunt’s electrical configuration (i.e., high or
low side). If any doubt exists as to the shunt’s location, use only ‘-DC4’
isolated-supply models. All rewiring must be performed with the load
and power supply de-energized.
6. Operation With 36 to 75Vdc Power:
As shipped, all ‘-DC1’ models’
rated operating supply range is +5 to +40Vdc. However, ‘-DC1’
models can be user configured for 36 to 75Vdc operation by removing
(opening) jumper J3. Please note that this modification can only be
performed on ‘-DC1’ power models. Also, all ‘-DC1’ models – including
those that have been modified for 36-75Vdc operation – can only be
connected in low-side, grounded-shunt applications. See Figure 3 for
DCA-20PC-X-DC4-XX
1
7. Decimal Points:
DCA-20PC ammeters’ decimal points are factory con-
figured for the respective full-scale input range. However, the decimal
points serve as placeholders only, they have no affect on the ammeter’s
displayed accuracy or resolution.
DCA-20PC-X-DC4-XX
1
CAL
SHUNT IS IN
HIGH SIDE
1
TB1
2
1
TB2
2
3
TB2-1 AND TB2-2
ARE INTERNALLY
SHORTED
–SHUNT
+SHUNT
+V
–V
+
LOAD
+
–
–
LOAD
CURRENT
DC SUPPLY #1
8-36Vdc
–
DC SUPPLY
#2
+
Figure 5. Using "-DC4" Isolated-Power Models to Maintain Isolation
Between Two Power Supplies
DCA-20PC-X-DC4-XX
1
CAL
CAL
SHUNT IS IN
HIGH SIDE
1
1
TB1
2
1
TB2
2
3
TB2-1 AND TB2-2
ARE INTERNALLY
SHORTED
SHUNT IS IN
LOW SIDE
TB1
2
1
TB2
2
3
TB2-1 AND TB2-2
ARE INTERNALLY
SHORTED
–SHUNT
–SHUNT
+SHUNT
+SHUNT
+V
+V
–V
+V
+V
–V
–
+
LOAD
LOAD
+
LOAD CURRENT
LOAD CURRENT
–
–
DC SUPPLY
8-36Vdc
+
–
DC SUPPLY
8-36Vdc
+
Figure 4. High-Side Shunt Connections for "-DC4"
8-36Vdc Isolated-Power Models
Figure 6. Using "-DC4" Isolated-Power Models
in Low-Side Shunt Applications
www.murata-ps.com/support
MPM_DCA-20PC.C01
Page 4 of 6
DCA-20PC Series
LED Display, Subminiature DC Ammeters with Built-In Shunts
TECHNICAL NOTES
If desired, an alternative decimal point by can be enable by opening the
factory closed solder gap and then closing one of the other two solder
gaps. The closing of SG1, SG2, or SG3 selects DP1 (“1.XXX”), DP2
(“1X.XX”), or DP3 (“1XX.X”), respectively.
8. 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 internal shunt. Even
though DCA-20PC ammeters incorporate built-in input filtering, some
portion of this noise may be amplified and subsequently measured by
its sensitive input circuitry. The amplified noise introduces errors that
are particularly noticeable at zero load current (i.e., the ammeter may
not display a relatively steady “000” reading).
Connecting an external, unpolarized capacitor across TB1’s -SHUNT
and +SHUNT inputs can help reduce noise-related display errors.
In certain situations, the use of twisted pair or shield wiring may be
required. As a general rule, avoid using excessively long leads between
the ammeter and the load.
9. ‘Power ON’ LED:
DCA-20PC ammeters include a rear-mounted ‘Power
On’ LED. The bright illumination of this LED indicates that the meter’s
internal power converter is operational. It does not signify that the
ammeter and the external load are connected correctly.
10. Measuring positive and negative currents (bipolar operation):
In applications where both positive and negative currents must be
measured, Murata Power Solutions recommends using ‘-DC4’ 8-36V
isolated supply models. Negative current flow is denoted by the
illumination of the display’s negative (-) sign; the absence of a negative
sign implies positive current flow. Contact Murata Power Solutions
if you have any questions regarding bipolar operation of DCA-20PC
ammeters. detailed wiring information. Any reconfiguration of J3 must
be made prior to connecting the power supply and load to the ammeter.
DCA-20PC-X-DC1-XX
1
CAL
J3
1
2
SHUNT
MUST BE
IN LOW SIDE
1
TB1
2
1
TB2
2
–SHUNT
(–V)
+SHUNT
+V
–
LOAD
+
LOAD CURRENT
–
DC SUPPLY
5-40Vdc
+
PANEL INSTALLATION
All connections and modifications must be made after the ammeter
is securely attached to the panel, with all load and supply voltages
de-energized (off).
The installed wire-positions should be such that minimal forces are applied
to TB1, TB2, and the ammeter itself. In high-vibration environments, the
use of wiring strain-reliefs is recommended.
To insure a secure panel-mount installation, MPS recommends using
the DMS-BZL4 (with sealing gasket) bezel assembly supplied with each
Figure 7. 3-Wire Connections for "-DC1"
5-40Vdc Powered Models
ammeter. See the Mechanical Specifications section for detailed panel
cutout and ammeter dimensions.
Following the four-step sequence shown in Figure 8 below, being careful
not to apply excessive force or twisting motions, insert the ammeter into
the panel opening. When using the DMS-BZL4’s sealing gasket, make
sure it is positioned between the ammeter’s flange and the panel’s front
surface. Be sure to use and securely tighten all four screws supplied with
the bezel assembly.
Step 1.
Step 2.
Step 3.
Step 4.
PANEL
PANEL
PANEL
PANEL
BEZEL
1
3
2
4
GASKET
(optional)
Figure 8. Panel Installation
www.murata-ps.com/support
MPM_DCA-20PC.C01
Page 5 of 6
Analog electronics
京公网安备 11010802033920号
EEWORLD
