Specifications

TECHNICAL NOTES
PANEL INSTALLATION
Step 1. Step 2. Step 3. Step 4.
All connections and modifi cations 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 8. Panel Installation
ammeter. See the Mechanical Specifi cations 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 fl ange and the panel’s front
surface. Be sure to use and securely tighten all four screws supplied with
the bezel assembly.
PANELPANELPANEL
2
1
PANEL
3
4
BEZEL
GASKET
(optional)
1
CAL
DCA-20PC-X-DC1-XX
1
2
TB2
1
2
TB1
–SHUNT
(–V)
–
–
+
+
+V
LOAD CURRENT
LOAD
DC SUPPLY
5-40Vdc
+SHUNT
SHUNT
MUST BE
IN LOW SIDE
1
2
J3
J3
Figure 7. 3-Wire Connections for "-DC1"
5-40Vdc Powered Models
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 signifi cant noise
onto the low-level signal developed across the internal shunt. Even
though DCA-20PC ammeters incorporate built-in input fi ltering, some
portion of this noise may be amplifi ed and subsequently measured by
its sensitive input circuitry. The amplifi ed 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, DATEL recommends using ‘-DC4’ 8-36V isolated supply
models. Negative current fl ow is denoted by the illumination of the
display’s negative (-) sign; the absence of a negative sign implies posi-
tive current fl ow. Contact DATEL if you have any questions regarding
bipolar operation of DCA-20PC ammeters. detailed wiring information.
Any reconfi guration of J3 must be made prior to connecting the power
supply and load to the ammeter.
www.murata-ps.com/support
DCA-20PC Series
LED Display, Subminiature DC Ammeters
with Built-In Shunts
MPM_DCA-20PC.B07 Page 5 of 6