ACA-20PC Series
Digital, LED-Display AC Ammeters with
Built-in Current Transformers
TECHNICAL NOTES
IMPORTANT!
To ensure safe and reliable operation, ACA-20PC
ammeters must be installed and serviced by qualified technical
personnel. Contact DATEL if there is any doubt regarding ammeter
installation and/or operation.
1. Measurement Type:
ACA-20PC ac ammeters employ a full-wave-
rectified, average responding, rms-calibrated circuit to measure the
stepped-down output of their on-board, L1 current transformer (CT) .
Stated accuracy specifications are measured using a sine-wave cur-
rent at or close to the specified full scale input level, at nominal line
frequency.
2. Calibration:
Periodic recalibration of ACA-20PC ammeters is not
required under normal, indoor operating environments. If user
calibration is necessary, it should be performed by qualified technical
personnel. Calibration is performed with potentially lethal voltages
applied to the ACA-20PC and its associated wiring, with the specified
full-scale current flowing through the ammeter’s built-in current
transformer.
A plastic, fully insulated adjusting tool must be used to access the
recessed calibration potentiometer located on the back of the meter
(see Mechanical Specifications). Contact DATEL if additional informa-
tion is required regarding calibration, setup, or any other technical
issue pertaining to the ACA-20PC.
3. Wire Gauges and Fusing:
Wires specified in the Functional Specifi-
cations section must be used for making connections to ACA-20PC
Series ammeters. All power-supply and load wiring must be rated for
the supply voltages and currents they will conduct and must comply
with any code or application-mandated requirements pertaining to
the user’s specific installation.
In particular, special attention must be paid to ACA-20PC-1-AC1-RL
and ACA-20PC-2-AC1-RL ac-powered models when their built-in
auxiliary terminal block connections (TB1) are used to supply current
to an external load. The supply wires connected to both the meter
and the load must be fused according to the current rating of the wire
gauge being used, in accordance with applicable regulatory codes.
Also, wire insulation should be stripped to within ±10% of the stated
dimensions, and wires should be inserted into TB1 such that their
insulation is not pinched by the screw terminal.
The ACA-20PC-3-ACX (0-50A range, ac-powered) and ACA-20PC-
4-ACX (0-100A, ac-powered) models’ TB1 is used only for powering
the meters' internal circuitry. It must not be used to supply current to
external loads. The supply wires feeding these meters must also be
fused according to the current rating of the wire gauge being used, in
accordance with applicable regulatory codes.
AC-powered models draw minimal steady-state supply currents
(50mA max.), and in most applications, they can be fused accord-
ing to the supply wire’s maximum amperage rating. However, these
models can draw significantly higher surge currents for brief periods
when the ac line voltage is initially applied.
4. AC Supply Polarity and Grounding:
The two ac supply inputs,
TB1-A and TB1-B, on ac-powered ammeters are not in themselves
polarity sensitive, that is, they have no internal "AC LO" or "AC HI"
designations. Also, ac-powered ACA-20PC ammeters do not include
or require a connection to earth/chassis ground. However, in many
applications, external ac loads which are connected directly to the
ACA-20PC’s built-in auxiliary terminal blocks must be wired with
proper polarity and connected to earth/chassis ground.
5. Connector Torque Ratings:
It is important to tighten TB1's screw
terminals to their rated torque specifications of 4.4 pound-inches
(0.5Nm) for four-terminal ammeters (ACA-20PC-1-AC1-RL and ACA-
20PC-2-AC1-RL), and 3.6 pound-inches (0.4Nm) for two-terminal
ammeters. Proper tightening will minimize connector losses and
ensure safe, reliable operation.
6. 100 Amp Model (ACA-20PC-4-XXX):
This model’s built-in current
transformer requires a larger panel cutout width dimension. See
Mechanical Specifications for more information.
7. DC-Powered Models:
DC-powered models draw minimal supply
currents and in most applications can be fused according to the
supply wire’s maximum amperage rating. However, be sure to check
and comply with all applicable codes and regulations to ensure
proper installation and operation.
8. Isolation:
The on-board CT (L1) provides a minimum 2000Vdc
isolation between the current-carrying conductor passing through its
primary circuit and the ammeter supply voltage connected to TB1. Of
course, this isolation rating only applies to applications in which the
load wiring (i.e., the wire passing through the CT’s center hole) does
not connect directly or indirectly to TB1-A or TB1-B.
PANEL INSTALLATION
All connections to ACA-20PC Series ammeters must be made
after the ammeter is securely attached to the panel and with all
load and supply voltages de-energized (off).
Care should be exercised when passing the load-carrying conduc-
tor through the meter’s built-in CT— particularly when larger-gauge
conductors are used. The position of the installed wire should be
such that minimal forces are applied to the built-in CT, TB1, or to
the ammeter itself. In high-vibration environments, adequate strain
reliefs be used for all load and supply wiring.
To ensure a secure panel-mount installation, DATEL recommends
using the DMS-BZL4 bezel assembly (with sealing gasket) supplied
with each ammeter. Also, please note that the ACA-20PC-4-XXX
100A oversize CT requires a larger panel-cutout width of 1.350"
(34.3mm). See Mechanical Specifications for detailed cutout and
ammeter dimensions.
Following the four-step sequence shown in Figure 2 below—being
careful not to apply excessive force or twisting motions—insert the
ammeter into the panel opening. When using the DMS-BZL4 bezel
assembly, install its sealing gasket so it is positioned between the
ammeter’s front flange and panel front surface (see Mechanical
Specifications). Be sure to use and securely tighten all four screws
supplied with the bezel assembly.
Technical enquiries
email: sales@murata-ps.com, tel:
+1 508 339 3000
www.murata-ps.com
MPM_ACA_20PC.B05
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MURATA-PS [ MURATA POWER SOLUTIONS INC. ]
