ACA-20RM-4-AC3-RL-ALM-C - Murata Power Solutions

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ACA-20RM-ALM Series

True-rms-AC Ammeters with Alarm Function

MPM_ACA-20RM-ALM.B01 Page 1 of 5

Murata Power Solutions’ ACA-20RM-ALM Series digital ac ammeters accurately display

the true-rms value of non-sinusoidal ac currents and provide a user-settable, over current

alarm function. When the preset over current level is exceeded, the LED display continu-

ously ﬂ ashes from high to low intensity. All models are totally self-contained—no other

user-supplied components are required. A built-in current transformer greatly simpliﬁ es

most ac ammeter applications: just pass the load conductor through the built-in current

transformer, apply ac power, and the ammeter is fully operational.

Two input ranges are available: 0-30.0 Amps, or 0 to 50.0 Amps, both with 0.1A resolu-

tion. The 50 Amp model features a convenient split-core type current transformer which

can be clamped around insulated live conductors. Two power supply options are available:

85-140V (47-63Hz), and 170-264V (47-63Hz). Power consumption from a nominal 120V or

220V ac supply is less than 50mA. Super-stable components and an rms-to-dc converter

circuit combine to achieve excellent performance when measuring the complex, non-sinu-

soidal, ac currents found in today’s computer/telecom equipment.

All ACA-20RM-ALM Series true-rms ammeters feature full-size, 0.37" (9.4mm) high,

3½ digit, bright red LED-displays and a built-in bezel/ﬁ lter assembly that includes metal

fasteners. They are also panel cutout compatible with MPS’s DMS-20RM Series of rms-

reading ac voltage monitors, making ACA-20RM-ALM ammeters the ideal upgrade for

today’s sophisticated instrumentation.

FEATURES

 User–settable, visual alarm function

 Flashing display indicates overcurrent faults

 Measures the true-rms value of complex ac current

waveforms

 Includes built-in current transformers

 Ideal for measuring current in sensitive IT applications

 Available in two input ranges: 0-30.0A, and 0 to 50A

 50A model features convenient split-core CT

 Easy-to-read, red LED display with 0.37"/9.4mm high

digits

 Two AC power options: 85-140Vac & 170-264Vac

(50/60Hz)

 2000V isolation between ac supply and load conductor

 Approvals to UL/cUL/IEC/61010-1

US E156931

CURRENT LIMITED

AC SUPPLY

3½ D IGIT

A/D CONVERTER

+V –V

–

RMS-to-DC

CONVERTER

CAL.

BUILT-IN

CURRENT

TRANSFORMER

LED DISPLAY

POWER

CONVERTER

TB1

(L1)

MEASURED AC

LOAD CURRENT

Figure 1. ACA-20RM-ALM Series simpliﬁ ed schematic

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ACA-20RM-ALM Series

True-rms-AC Ammeters with Alarm Function

MPM_ACA-20RM-ALM.B01 Page 2 of 5

TECHNICAL NOTES

IMPORTANT! To ensure safe and reliable operation, ACA-20RM-

ALM ammeters must be installed and serviced by qualiﬁ ed

technical personnel. Contact Murata Power Solutions if there is

any doubt regarding ammeter setup, installation, or operation.

1. Measurement Type: ACA-20RM-ALM ac ammeters employ a

true-rms input circuit to measure current ﬂ owing through L1. Stated

accuracy speciﬁ cations are measured using a sine-wave current

at, or close to, the ammeter’s full-scale input range, at nominal line

frequency of 60Hz.

2. Calibration (Potentiometer R7): Periodic recalibration of ACA-

20RM-ALM ammeters is not required under normal, indoor operating

environments. If user calibration is necessary, it must be performed

by qualiﬁ ed technical personnel. Calibration is performed with poten-

tially lethal voltages applied to the ACA-20RM-ALM and its associated

wiring. A plastic, fully-insulated adjusting tool must be used to access

the calibration potentiometer R7 located on the back of the ammeter

(see ‘Mechanical Speciﬁ cations’ section). Contact MPS if additional

information is required regarding calibration, setup, or any other

technical issue pertaining to ACA-20RM-ALM ammeters.

3. Overcurrent Alarm Setup and Adjustment (Potentiometer R3):

ACA-20RM-ALM ammeters feature a user-settable, overcurrent visual

alarm indication which can be used to alert operators that a load cir-

cuit breaker or fuse is approaching an overload condition. When the

load current sensed by L1 exceeds this preset level, the ammeter’s

LED display will ﬂ ash from normal intensity to dim intensity at rate of

approximately 1.5 times per second.

As shown in Figure 3, the alarm circuit consists of jumper JP1, and

adjustment potentiometer R3. As shipped, R3 is factory set to trip

when the load current is approximately 24 Amps for 30A models, and

approximately 45 Amps for 50A models. When R3 is set to its maxi-

mum clockwise position, the alarm indication will not activate until the

load current ﬂ owing through L1 exceeds the maximum rating of the

ammeter, i.e., above 30.0A, or above 50.0A, depending on the model.

Performance/Functional Speciﬁ cations

Typical at TA = +25°C, unless otherwise noted.

➀ Speciﬁ ed full-scale currents are those passing through the ammeter’s built-in

current transformer’s primary load-circuit. See Notes 2 and 3 below for ad-

ditional model-speciﬁ c information.

➁ The overcurrent rating of 1.5 x the rated full-scale current is a continuous rating

and applies to the current passing through the built in current transformer only,

it does not apply to any external circuit-wiring or external loads. Accuracy is

guaranteed up to the rated current level.

➂ Speciﬁ ed accuracy applies to inputs with crest factors (CF) up to 2.0, where CF

= Vpeak/Vrms. Crest factors of 2 to 5 introduce an additional error of ±3% of full

scale. Ammeters are calibrated with a near full-scale 60Hz sine-wave current

ﬂ owing through the ammeter’s built-in CT.

➃ All speciﬁ ed maximum power supply currents are steady state; larger surge

currents can occur at initial application of line power.

Rated Full-Scale Current ➀Min. Typ. Max. Units

ACA-20RM-4-ACX-RL-ALM — — 50.0 Amperes

ACA-20RM-5-ACX-RL-ALM — — 30.0 Amperes

Overcurrent Rating ➁1.5 x Rated Full-Scale Current

Performance

Sampling Rate 2.5 Samples per second

Accuracy ➂±0.4%FS ±3 Counts with 60Hz

Sine-Wave Input

Measurement Type rms Responding, Crest Factors of 1-5

Temperature Drift (0 to 60 °C) — ±0.2 ±0.4 Counts/ºC

Zero-Current Reading (within

30 sec.)

–001 000 001 Counts

Dielectric Withstanding Voltage 2000 — — Vdc

UL/IEC61010-1 Measurement category II

Power Supply Voltage

ACA-20RM-X-AC3-RL-ALM 85 120 140 Vac/47-63Hz

ACA-20RM-X-AC4-RL-ALM 170 220 264 Vac/47-63Hz

Power Supply Current ➃

ACA-20RM-X-AC3-RL-ALM — 30 50 mA/47-63Hz

ACA-20RM-X-AC4-RL-ALM — 30 50 mA/47-63Hz

Alarm Function

Display indication Flashing Display with actual current

reading and display intensity change

Settable range

ACA-20RM-4-ACX-RL-ALM 13 45 50 Amps

ACA-20RM-5-ACX-RL-ALM 8 24 30 Amps

Power Supply Terminal Block

Wire Size 16-22AWG, Solid or stranded

Insulation Strip Length 0.250 inches

Screw Tightening Torque 3.6 pounds-inches (0.4Nm)

Rated Voltage 310Vac

Display

Display Type and Size 3½ Digit Red LED, 0.37”/9.4mm High

Overrange Indication “1___”

Decimal Point Fixed, model dependent

(see full-scale input current)

Physical/Environmental

Operating Temperature 0 — +60 °C

Storage Temperature –40 — +75 °C

Humidity (non-condensing) 0 — 85 %

Dimensions Model dependent, see page 4 & 5

Weight

ACA-20RM-4-XXX-XX-ALM 1.5 Ounces (43 grams) nominal

ACA-20RM-5-XXX-XX-ALM 2.1 Ounces (60 grams) nominal

Ordering Information

ACA-20RM-4-AC3-RL-ALM-C 50.0A Range (split-core CT), 85-140Vac power

ACA-20RM-4-AC4-RL-ALM-C 50.0A Range (split core CT), 170-264Vac power

ACA-20RM-5-AC3-RL-ALM-C 30.0A Range, 85-140Vac power

ACA-20RM-5-AC4-RL-ALM-C 30.0A Range, 170-264Vac power

See www.murata-ps.com/dpm-availability for model-speciﬁ c availability.

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ACA-20RM-ALM Series

True-rms-AC Ammeters with Alarm Function

MPM_ACA-20RM-ALM.B01 Page 3 of 5

7. Isolation: The built-in current transformer L1 provides a minimum

of 2000Vdc isolation between the load conductor and the ammeter’s

supply voltage connected to TB1.

8. Split-Core CT (Clamp-on) Models: Both 50A models feature a split-

core current transformer that can be clamped around a properly insu-

lated live conductor without having to disconnect or remove power

from the load circuit. This live-connection capability can only be used

if the load’s power source is electrically isolated (see technical note

7) from the ammeter’s own power source that’s connected to TB1.

The ammeter’s ac power supply must always be denergized before

making connections to TB1. Refer to the ‘Panel Installation’ section of

this data sheet for additional information.

TO AC LOAD

TB1

BACK VIEW

FUSED AC POWER

Figure 2. Typical wiring diagram

To adjust the overcurrent alarm set-point level:

A. Turn off power to the ACA-20RM-ALM (i.e., the power source con-

nected to TB1).

B. Carefully remove the shorting jumper across JP1 from its ‘normal

operation position’ across terminals 2 and 3 and place it across JP1

terminals 1 and 2.

C. Re-apply power to TB1 and, using a plastic insulated adjusting tool,

adjust R3 so the ammeter’s display shows the desired overcurrent

trip level in Amps.

D. Turn off power to the ACA-20RM-ALM and return JP1’a shorting

jumper back to its ‘normal operation position’ across terminals 2

and 3. Re-apply power to TB1 to resume normal operation. If pos-

sible, after the ammeter is re-conﬁ gured for normal operation, the

load current should be slowly increased to verify the visual alarm

operates when the load current exceeds the preset level.

Please note, the load circuit does not need to be turned off to adjust the

overcurrent alarm set point. Current ﬂ owing through L1 while JP1 is

across terminals 1 and 2 will not be measured. Once tripped, the alarm

set point function has a hysteresis of approximately 0.5A.

The overcurrent alarm function can also be adjusted with JP1 in its

normal operation position if the desired alarm overcurrent-level is

actually ﬂ owing through L1 (i.e., with a live load). For example, with

a 20 Amp load current ﬂ owing through L1, and with JP1 in its normal

operation position, slowly adjust R3 until the display starts ﬂ ashing on

and off. Using this “live load” adjustment method eliminates the need

to turn off power to TB1 or reconﬁ guring JP1.

4. Wire Gauges and Fusing: Wires speciﬁ ed in the Functional Speciﬁ ca-

tions section must be used for making connections to ACA-20RM-ALM

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 speciﬁ c installation.

ACA-20RM-ALM ammeters are not internally fused. Terminal block TB1

is to be used only for powering the ammeter’s internal circuitry; it must

not be used to supply power to external loads. The supply wires feed-

ing these power meters must be fused with a 0.25A/250V time delay/

time lag fuse, in accordance with applicable regulatory codes.

Wire insulation must be stripped to within ±10% of the stated dimen-

sions, and wires should be inserted into TB1 such that their insulation

is not pinched by the screw terminal.

5. AC Supply Polarity and Grounding: The two supply inputs, TB1-A and

TB1-B, on ACA-20RM-ALM ammeters are not in themselves polarity

sensitive, that is, they have no internal “AC LO” or “AC HI” designa-

tions. ACA-20RM-ALM ammeters do not include or require a connec-

tion to earth/chassis ground.

6. Connector Torque Ratings: It is important to tighten TB1’s, screw-ter-

minals to their rated torque speciﬁ cation of 3.6 pound-inches (0.4Nm).

Proper tightening will minimize connector losses and ensure safe,

reliable operation.

Figure 3. Alarm circuit component location

TB1 R7

CAL

JP1

BACK VIEW

ALARM

JP1

Normal Operation

JP1

Overcurrent

Alarm Adjustment

F R O N T V I E W

1 . 2 8 0

( 3 2 . 5 1 )

0 . 1 8 7

( 4 . 7 5 )

R E C O M M E N D E D D R I L L A N D

P A N E L C U T O U T D I M E N S I O N S

1 . 8 2 6 ( 4 6 . 3 8 )

0 . 8 3 8

( 2 1 . 2 9 )

1 . 6 2 6 ( 4 1 . 3 0 )

1 . 0 7

( 2 7 . 1 8 )

I N T E R N A L C O R N E R R A D I I :

0 . 0 3 2 ( 0 . 8 1 ) M A X .

0 . 0 9 3 ( 2 . 3 6 2 ) D I A M E T E R ( 4 R E Q U I R E D )

0 . 1 1 6 ( 2 . 9 5 )

1 . 3 3 6 ( 3 3 . 9 3 ) 0 . 1 4 5 ( 3 . 6 8 )

0 . 69

(17.5)

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ACA-20RM-ALM Series

True-rms-AC Ammeters with Alarm Function

MPM_ACA-20RM-ALM.B01 Page 4 of 5

PANEL INSTALLATION

BEZEL AND PANEL CUTOUT

All connections to ACA-20RM-ALM Series ammeters must be made after

the ammeter is securely attached to the panel and with all associated

load and supply voltages de-energized (off), using extreme caution and

observing all safety measures applicable to the user’s installation.

Care should be exercised when passing conductors through the amme-

ter’s built-in current transformer L1. The installed wire-positions should

be such that minimal mechanical forces are applied to L1, TB1, or to the

ammeter itself. In high-vibration environments, it is strongly recom-

mended that adequate strain reliefs be used for all wiring.

Using Figure 4 as a guide, carefully insert the bezel/color ﬁ lter assembly

into the panel opening. From the rear of the panel, install the four round

Figure 4. Panel Installation

plastic standoffs over the bezel’s threaded studs. Install the ACA-20RM-

ALM pc-board assembly as shown and then attach and securely tighten

each of the four hex nuts to 15-20 ozf-in (0.106 to 0.140 N-m). Use only

the factory-supplied hardware as the use of substitute hardware could

result in an unsafe installation and/or adversely affect the reliability of

the ammeter.

The recommended range of panel thickness that can be used with the

supplied hardware is 0.040 inches (1.0mm) to 0.125 inches (3.2mm).

Panel thickness outside of this range will require additional user-supplied

hardware or modiﬁ cations.

SIDE VIEW

Bezel

Gasket Standoff

Nut

ACA-20RM

AC Ammeter

Board-Cutout

PANEL

Gasket Standoff

0.190 (4.83)

0.032 (0.8) Thick

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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. Speciﬁ cations are subject to change without

Murata Power Solutions, Inc.

11 Cabot Boulevard, Mansﬁ eld, MA 02048-1151 U.S.A.

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: http://www.murata-ps.com/requirements/

ACA-20RM-ALM Series

True-rms-AC Ammeters with Alarm Function

MPM_ACA-20RM-ALM.B01 Page 5 of 5

MECHANICAL SPECIFICATIONS

MECHANICAL DIMENSIONS: Inches (mm)

TOLERANCES: 2 PL DEC ±0.02 (±0.51)

3 PL DEC ±0.010 (±0.254)

FRONT VIEW

BACK VIEW

SIDE VIEW

100-10

2.100

(53.34)

1.400

(35.56)

0.250

(6.35)

30 AMP MODELS

0.480

(12.19)

Lead Length

2.0 (50.5) min.

0.35

(8.9)

Diameter

FRONT VIEW

BACK VIEW

SIDE VIEW

100-10

2.100

(53.34)

1.400

(35.56)

0.250

(6.35)

50 AMP SPLIT-CORE CT MODELS

1.024

(26.01)

0.551

(14.00)

0.984

(24.99)

1.575

(40.00)

0.480

(12.19)

0.40

(10.2)

Diameter

Lead Length

5.0 (127.0) min.

TB1

1. Description of safety marks:

Caution, risk of electrical shock

Caution, risk of danger

Equipment is protected throughout by double or reinforced insulation

2. Cleaning Instructions: Gently clean with dry cloth only.

3. Caution: if the equipment is used in a manner not speciﬁ ed by Murata Power Solutions, the protection provided by the equipment may be impaired.

Mouser Electronics

Authorized Distributor

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ACA-20RM-4-AC3-RL-ALM-C ACA-20RM-4-AC4-RL-ALM-C ACA-20RM-5-AC4-RL-ALM-C ACA-20RM-5-AC3-RL-

ALM-C