ACM20-5-AC1-R-F-C - MURATA POWER SOLUTIONS

Murata Power Solutions’ ACM20 series AC power meters display the most critical measure-

ments in mains-powered equipment: voltage, amperage, active power (watts), and power

factor. A front panel selector-switch provides two modes of operation: a ﬁxed reading of

any of the four parameters, or a continuous cycling through all four measurements. An

optional model displays line frequency with 0.1Hz resolution. All ACM20 multi-function

power meters include built-in current transformers—no other user-supplied components

are required.

ACM20 series AC power meters are available in a choice of three input ranges: 0-10A (with

0.001A resolution, 999.9 watts max.); 0-32A (with 0.01A resolution, 9999 watts max.); and

0-100A (0.1A resolution, 26.4kW max.). An 85-264Vac (47-63Hz) operating supply range

makes these power meters perfect for worldwide power monitoring applications. And,

unlike conventional, average-responding products, ACM20 power meters can accurately

display the real power and true-rms current values of triangle waves, square waves, and

other irregularly shaped waveforms, with a typical accuracy of ±1% of full scale.

Their large (0.36"/9.2mm), bright red LED display makes ACM20 AC power meters easily

readable from as far as 15 feet (5 meters). All units are packaged in a one-piece, vibration

resistant, polycarbonate housing that can be installed in vertical ‘0U’ and ‘1U’ rack spaces.

Their miniature size is perfect for UPS power sources, power strips, laboratory instrumenta-

tion, alternative energy applications, and any other products that require precise monitoring

of AC power.

PRODUCT OVERVIEW

FEATURES

n

Displays AC Volts, Amps, Watts, and Power Factor or Hertz

n

Two display modes: continuous auto cycling or ﬁxed

n

Universal 85-264Vac (47-63Hz) operating range

(Measurement Category II)

n

Built-in current transformers simplify installation; choice of

10A, 32A, or 100A ranges

n

Ideal for power distribution units (PDUs) and power strips

n

True-rms readings of complex voltage and current waveforms

n

Low-power consumption: less than ¼watt from 120Vac

n

One-piece polycarbonate housing ﬁts ‘0U’ & ‘1U’ racks

n

Surface mount design occupies minimal panel space

n

Bright red LED-display with four annunciators

n

Optional Frequency reading models (0.1Hz resolution)

n

Approvals to UL/CSA/IEC/EN 61010-1

SIMPLIFIED SCHEMATIC DIAGRAM

85-264 Vac

47-63 Hz

AC/DC

CONVERTER

CURRENT

LIMITED

SUPPLY

MICRO-

CONTROLLER

SEL

+5V

A/D

CONVERTER

LOAD CURRENT

VOLTS AMPS WATTS PF

Actual size

US E156931

New!

Low-Wattage

Models

Available

www.murata-ps.com

www.murata-ps.com/support

For full details go to

www.murata-ps.com/rohs

ACM20 Series

Four-Function AC Power Meters

MPM_ACM20 Series.D02 Page 1 of 7

Measurement Limits Min. Typ. Max. Units

AC Voltage 85.0 - 264.0 Volts

AC Current, 10A models (1)

AC Current, 32A models (1)

AC Current, 100A models (1)

0.00

0.0

9.999

32.00

100.0

Amperes

Active Power: 10A models

Active Power: 32A models

Active Power: 100A models

999.9

9999

26.4

Watts

Frequency 47.0 - 63.0 Hz

Power Factor .00 1.00 - -

Overcurrent Rating (2) 1.5 x rated full-scale current

Performance

Sampling Rate 2-3 samples / sec

Voltage Accuracy (3) ±1%

Current Accuracy (3) ±1%

Power Accuracy (3) ±2%

Frequency Accuracy (3) ±0.1 Hz

Power Factor Accuracy ±3%

Measurement Bandwidth 140Hz (Voltage), 14kHz (Current)

Temperature Drift (0 to 60ºC) 0.5 Counts/ºC

Zero-Current Reading (within 2 sec.) 0.00 Amps

Zero-Power Reading (within 2 sec.) 0 Watts

UL/IEC61010-1 Measurement category II

Supply Voltage (TB1) (Measurement Category II)

All Models – 47-63 Hz 85 120 264 Vac

Supply Current (4)

All Models 35 50 110 mA

Power Supply Terminal Block

Wire Size 16-22AWG, solid or stranded

Insulation Strip Length 6.4mm (0.250 in)

Screw Tightening Torque 0.4Nm (3.6 lb-in)

Rated Voltage 300Vac

Display

Display Type and Size 4 Digit LED, 9.14mm (0.36in) high

Overrange Indication Flashing ‘9999’ Watts (5)

Decimal Point Selection Automatically Set

Physical/Environmental

Operating Temperature 0 – +60 °C

Storage Temperature –40 – +75 °C

Humidity (non-condensing) 0 – 85 %

Dimensions See mechanical speciﬁcations

Weight: 32A models

Weight: 100A models

1.3oz (37.9g)

1.5oz (43.5g)

Hex Nut Tightening Torque 0.14 N-m (20 ozf-in)

(1) Speciﬁed full-scale currents are those passing through the power meter’s built-in current

transformer’s primary load-circuit.

(2) 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. Accuracy is guaran-

teed up to the rated current.

(3) ACM20 Power Meters are calibrated with near full-scale 60Hz sine-wave inputs.

(4) All speciﬁed maximum supply currents are steady state; larger surge currents can occur at

initial application of line power.

(5) Applies to 10A and 32A models only.

Performance/Functional Speciﬁcations

Typical at TA=+ 25ºC, 120Vac @ 60Hz, unless otherwise noted

ORDERING INFORMATION

See page 7 for all active part numbers and descriptions.

TECHNICAL NOTES

IMPORTANT! To ensure safe and reliable operation, ACM20 power

meters must be installed and serviced by qualiﬁed technical person-

nel. Contact Murata Power Solutions if there is any doubt regarding

their installation or operation.

1. Measurement Type: ACM20 series multifunction AC power meters

employ a precision energy metering integrated circuit and a low-

power microcontroller to measure and display the rms voltage and

current, active (real) power, power factor (or line frequency on ‘–F’

sufﬁx models) of ac mains supplies from 47-63Hz. Please note,

ACM20 power meters use the voltage present at their TB1 terminal

block and the secondary current of their built-in current transformer

L1 to calculate and then display VOLTS, AMPS, WATTS, power factor

(PF), or line frequency on ‘-F’ HERTZ models.

While the ACM20 displays the rms value of line voltage and line

current, the VOLTS reading has an upper limit of 140Hz (-3db point),

which means rectangular-shaped voltage waveforms, and waveforms

with sharp transitions, will read lower than their true-rms value. For

example, a square wave line voltage will read approximately 1-2%

lower, a triangle wave will read 3% lower, and a modiﬁed sine wave

will read 18% lower. The oscillograms on page seven illustrate typical

ACM20 VOLTS readings when powered from four ac waveforms.

The 140Hz bandwidth limit does not apply to the WATTS reading nor

to the AMPS reading. The circuitry used for these two measurements

has an upper bandwidth of 14kHz. ACM20 power meters are mains

operated devices designed to measure ac currents and voltages,

within the speciﬁed limits previously noted. DC currents and voltages

will not be measured accurately.

2. Basic Operation: Upon application of ac power to TB1, the unit will

ﬁrst perform a self-test routine and then continuously display ac volts

with the VOLTS LED annunciator illuminated. The display will remain

in the VOLTS mode as long as the front panel ‘SEL’ button is not

touched.

After the unit powers up to normal operation in the VOLTS reading

mode, momentarily (approximately one second) touching the ‘SEL’

button on the unit’s front panel three times in succession will cycle

the display to AMPS, WATTS, and end at PF (or HERTZ for ‘–F’ mod-

els). Momentarily touching ‘SEL’ a fourth time will return the display

back to the VOLTS reading mode.

Holding the ‘SEL’ button down for 3 seconds will place the unit in a

continuous auto-cycling mode, and the display will repetitively scroll

through all four measurements, with each measurement remaining

displayed for 3 seconds.

When the continuous auto-cycling mode is initially selected, the unit

will brieﬂy display ‘Auto On’ before continuous cycling begins. Mo-

mentarily touching the ‘SEL’ button again will cause the unit to brieﬂy

display ‘Auto OFF’ before it returns to the ﬁxed VOLTS reading mode.

www.murata-ps.com/support

ACM20 Series

Four-Function AC Power Meters

MPM_ACM20 Series.D02 Page 2 of 7

Displaying a speciﬁc mode on power up: Units manufactured after

February 2012 can be conﬁgured to automatically show any one

of the four display modes upon future applications of ac power. For

example, it may be desirable to conﬁgure the unit to always power up

in the AMPS mode.

To set the unit to always read AMPS on power up, tap the SEL switch

until the AMPS mode is displayed, and then leave the unit in this mode

for at least 60 seconds. As long as the SEL switch is not pressed

again during the 60 second interval, the unit will conﬁgure itself to

always power up displaying the chosen mode, which is AMPS in this

example.

In summary, operating the unit undisturbed in a particular display

mode for 60 seconds or longer will automatically conﬁgure the unit

to display that particular mode the next time ac power to the unit is

cycled off and back on. This functionality also applies to the auto-

cycle mode, that is, the unit can be conﬁgured to always power up in

the auto-cycle (scrolling) display mode by following the instructions

outlined above.

3. Calibration: Due their digital design, ACM20 power meters cannot be

calibrated in the ﬁeld. ACM20 power meters are factory-calibrated to

meet their speciﬁed accuracies with the supplied L1 current trans-

former. Use of any other current transformer will produce signiﬁcant

errors for the Amps, Watts, and Power Factor measurements.

Contact Murata Power Solutions if additional information is required

regarding calibration, setup, or any other technical issue pertaining to

ACM20 power meters.

4. Wiring: All power supply wiring must be rated for the voltages and

currents they will carry and must comply with any code or application-

mandated requirements pertaining to the user’s speciﬁc installation.

5. Supply Fusing, and Grounding: Wires speciﬁed in the Functional

Speciﬁcations section must be used for making connections to

ACM20 series power meters. No connection is required for earth/

chassis ground.

TYPICAL WIRING DIAGRAMS

H N

TB1

120 Vac (50/60 Hz)

120 V

LOAD

Epoxy encapsulation

Polarity dot on bottom

Fuse*

Figure 1. Wiring diagram for 110/120V single phase systems

ACM20 series power meters are not internally fused. Terminal block

TB1 is to be used only for powering the power meter's internal circuitry;

it must not be used to supply power to external loads. The supply wires

feeding these power meters must be fused with a 0.5A/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.

6. Current Transformer Polarity: In order to perform accurate Watts

and Power Factor measurements, connections to the two rear power

supply inputs, TB1-A and TB1-B, and built-in current transformer L1

must have the proper polarity. That is, the load current ﬂowing in the

wire passing through L1's center hole must have the same polarity as

the line voltage connected to TB1-A and TB1-B.

The wiring diagrams in Figures 1-4 ensure that, for a purely resistive

load, current ﬂowing in current transformer L1’s primary circuit will

have the same polarity as the applied voltage at TB1. If proper polarity

is not followed, the Watts and Power Factor readings will be zero. To

correct a zero Watts reading, simply reverse the direction of the load

wire passing through the hole in L1.

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

terminals to their rated torque speciﬁcation of 3.6 pound-inches

(0.4Nm). Proper tightening will minimize connector losses and ensure

safe, reliable operation.

8. Isolation: Except for the 2-56 thread metallic mounting studs, all of

the ACM20 power meter’s internal components (printed circuit board,

resistor, capacitors, current transformer L1’s secondary leads, etc.)

are at the ac-mains potential connected to TB1. ACM20 power meters

are designed to measure and be powered from one ac power-source

only. Any other connection schemes will introduce signiﬁcant mea-

surement errors.

Note: If the ACM20 displays zero Watts with

power applied to the load, reverse the direction

of the wire passing through the CT's center hole.

See Technical Note 6 for more information.

*See technical note 5.

www.murata-ps.com/support

ACM20 Series

Four-Function AC Power Meters

MPM_ACM20 Series.D02 Page 3 of 7

TYPICAL WIRING DIAGRAMS, CONT.

L1 L2

220 V

LOAD

220 Vac (50/60 Hz)

TB1

oxy encapsulation

olarity dot on bottom

Fuse*

Figure 2. Wiring diagram for 220/240V systems with no neutral

Figure 3. Wiring diagram for 120/240V systems with neutral (monitoring L1)

L1 Neutral L2

120 V

LOAD

220 Vac (50/60 Hz)

TB1

Fuse*

oxy encapsulation

olarity dot on bottom

Figure 4. Wiring diagram for 120/240V systems with neutral (monitoring L2)

L1 Neutral L2

120 V

LOAD

220 Vac (50/60 Hz)

TB1

Fuse*

oxy encapsulation

olarity dot on bottom

Note: If the ACM20 displays zero Watts with

power applied to the load, reverse the direction

of the wire passing through the CT's center hole.

See Technical Note 6 for more information.

Note: If the ACM20 displays zero Watts with

power applied to the load, reverse the direction

of the wire passing through the CT's center hole.

See Technical Note 6 for more information.

Note: If the ACM20 displays zero Watts with

power applied to the load, reverse the direction

of the wire passing through the CT's center hole.

See Technical Note 6 for more information.

*See technical note 5.

www.murata-ps.com/support

ACM20 Series

Four-Function AC Power Meters

MPM_ACM20 Series.D02 Page 4 of 7

PANEL INSTALLATION

All connections to ACM20 power meters must be made after the unit

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

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

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

Care should be exercised when passing conductors through the

power meter’s built-in current transformer L1. The installed wire-

positions should be such that minimal mechanical forces are applied

to current transformer L1, TB1, or to the ACM20 power meter itself.

In high-vibration environments, it is strongly recommended that

adequate strain reliefs be used for all wiring.

Using Figure 5 as a guide, carefully insert the ACM20 assembly into

the panel opening. From the rear of the panel, install and then tighten

the four #2-56 hex nuts over the threaded studs. Tighten each nut to

15 to 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 installation.

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

supplied hardware is 0.040 inches (1.0mm) to 0.25 inches (6.4mm).

Panel thicknesses outside of this range may require additional user-

supplied hardware or modiﬁcations. Front panel space permitting,

ACM20 power meters will ﬁt most existing ACA-20RM / ACA-20PC

ammeter cutouts, allowing for easy upgrading of existing installations.

Figure 5. Panel Installation

SIDE VIEW

2-56 Hex Nuts (4 places)

Tighten each nut to

15 to 20 ozf-in (0.106 to 0.140 N-m).

ACM20

Panel Cutout

PANEL

PANEL CUTOUT

RECOMMENDED DRILL AND PANEL CUTOUT DIMENSIONS

INTERNAL CORNER RADII:

0.032 (0.81) MAX.

1.07

(27.18)

0.838* - 0.870

(21.29* - 22.10)

1.336* - 1.426

(33.93* - 36.22)

1.626 (41.30)

0.093 (2.362) DIAMETER (4 REQUIRED)

* The two dimensions marked with an * specify the

minimum recommended panel cutout opening for

ACM20 power meters. Space permitting, the larger

dimensions noted (0.87in., and 1.426in.) should be

used. The panel opening must be centered vertically

and horizontally between the four 0.093 (2.362mm)

diameter holes.

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 speciﬁed by Murata Power Solutions, the protection provided by the equipment may be impaired.

www.murata-ps.com/support

ACM20 Series

Four-Function AC Power Meters

MPM_ACM20 Series.D02 Page 5 of 7

MECHANICAL SPECIFICATIONS

OSCILLOGRAMS

The graphs below show typical ACM20 power meter VOLTS readings when the unit is powered from four common ac-voltage waveforms.

V O LT S

AC POWER METER

AMPS WAT T S

SEL

1.43

(36.3)

2.10 (53.3)

Front View

Back View

0.51

(12.95)

1.07

(27.20)

0.40

(10.16)

0.12 (3.05) (min)

Side View

1.63

(41.4)

0.086 DIA (REF)

2-56 UNC THREAD

0.33 (8.39)

(min)

0.22 (5.59)

(min)

0.60

(15.24)

(max)

Bottom View

TB1

Diameter:

10A and 32A models: 0.35 (8.9)

100A models: 0.57 (14.5)

CT Lead Length:

Standard: 2.0” (50.5mm) min.

32A blue LED model: 20.0” (500mm) min.

100A blue LED model: 28.0” (710mm) min.

www.murata-ps.com/support

ACM20 Series

Four-Function AC Power Meters

MPM_ACM20 Series.D02 Page 6 of 7

ORDERING INFORMATION

ACM20-2-AC1-R-C 10A, 85-264Vac Supply (Power Factor Reading)

ACM20-5-AC1-R-C 32A, 85-264Vac Supply (Power Factor Reading)

ACM20-4-AC1-R-C 100A, 85-264Vac Supply (Power Factor Reading)

ACM20-2-AC1-R-F-C 10A, 85-264Vac Supply (Frequency Reading)

ACM20-5-AC1-R-F-C 32A, 85-264Vac Supply (Frequency Reading)

ACM20-4-AC1-R-F-C 100A, 85-264Vac Supply (Frequency Reading)

ACM20-5-AC1-B-20-C 32A, 85-264Vac Supply (Power Factor Reading), 20 inch lead length

ACM20-4-AC1-B-28-C 100A, 85-264Vac Supply (Power Factor Reading), 28 inch lead length

ACM20-4-AC1-B-C 100A, 85-264Vac Supply (Power Factor Reading)

ACM20-5-AC1-G-F-C 32A, 85-264Vac Supply (Frequency Reading)

www.murata-ps.com/support

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. Speciﬁcations are subject to change without

Murata Power Solutions, Inc.

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/

ACM20 Series

Four-Function AC Power Meters

MPM_ACM20 Series.D02 Page 7 of 7