Specifications

TECHNICAL NOTES
Figure 2A. Low-Side Shunt Connections for "-DC1"
5-40Vdc Non-Isolated Supply Models
Figure 3. Low-Side Shunt Connections for "-DC1"
Models Modifi ed for 36-75Vdc Non-Isolated Power
(See Technical Note 6)
To ensure safe and reliable operation, DCA-20PC dc ammeters
must be installed and serviced by qualifi ed 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 DATEL if
you have any questions regarding installation or operation of any
of our digital instruments.
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 fi nal
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 specifi cation
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 fi re 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 fl owing 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.
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 qualifi ed 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-specifi c wiring diagram shown later
in this data sheet. Using an insulated slotted tool, adjust the calibration
potentiometer until the display is within ±1 count of the desired read-
ing. Please note, the potentiometer provides an adjustment range of
approximately ±1%. Contact DATEL 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 Specifi cations
section for detailed wire type and wire gauge information.
1
CAL
DCA-20PC-X-DC1-XX
SHUNT
MUST BE
IN LOW
SIDE
TB2-1 & TB2-2
INTERNALLY
SHORTED
1
2
TB2
1
2
TB1
–SHUNT
(–V)
–
–
+
+
+V
+V
LOAD CURRENT
LOAD
DC SUPPLY
5-40Vdc
+SHUNT
1
2
J3 MUST BE
INSTALLED
(FACTORY
SETTING
FOR 5-40Vdc
SUPPLIES)
J3
J3
1
CAL
DCA-20PC-X-DC1-XX
SHUNT
MUST BE
IN LOW
SIDE
TB2-1 & TB2-2
INTERNALLY
SHORTED
1
2
TB2
1
2
TB1
–SHUNT
(–V)
–
–
+
+
+V
LOAD CURRENT
LOAD
DC SUPPLY #1
5-40Vdc
+SHUNT
1
2
J3 MUST BE
INSTALLED
(FACTORY
SETTING
FOR 5-40Vdc
SUPPLIES)
J3
J3
–
+
DC SUPPLY #2
(For Load Only)
1
CAL
DCA-20PC-X-DC1-XX
SHUNT
MUST BE
IN LOW
SIDE
TB2-1 & TB2-2
INTERNALLY
SHORTED
REMOVE J3
FOR 36-75Vdc
SUPPLIES
1
2
TB2
1
2
TB1
–
–
+
+
LOAD
DC SUPPLY
36-75Vdc
–SHUNT
(–V)
+V
+V
LOAD CURRENT
+SHUNT
1
2
J3
J3
Figure 2B. Low-Side Shunt Connections for "-DC1"
Models using Two Power Supplies
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DCA-20PC Series
LED Display, Subminiature DC Ammeters
with Built-In Shunts
MPM_DCA-20PC.B07 Page 3 of 6