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DMS-20RM Series

True-rms ac Voltmeters with Isolated Inputs

MPM_DMS-20RM.A02 Page 2 of 4

voltmeters must be installed and serviced by qualified technical personnel.

Contact Murata Power Solutions if there is any doubt regarding installation

and/or operation.

TECHNICAL NOTES

1. Measurement Type: DMS-20RM series ac voltmeters employ a preci-

sion rms-to-dc converter and a high-precision voltage reference to

measure and display the rms value of complex ac waveforms. Please

note, the rear-mounted potential transformer is used to isolate the

input signal being measured (TB2) from the ammeter’s operating power

source connected to TB1. Do not pass any conductors through this

transformer’s center hole as this will introduce significant measure-

ment errors.

2. Wiring: All power supply and input signal 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.

3. Power Supply Polarity, Fusing, and Grounding: As shown in Figures

1A and 1B, the two power supply inputs, TB1-A and TB1-B, on ac-pow-

ered DMS-20RM voltmeters (“-AC1” suffix) are not polarity sensitive,

that is, they have no “AC LO” or “AC HI” designations. Also, ac-powered

models do not include or require a connection to earth/chassis ground.

DC-powered models (‘-DC2’ suffix) are reverse-polarity protected, and

must be connected as shown in Figure 2 for proper operation.

DMS-20RM ac voltmeters are not internally fused. If fusing is required

it must be externally installed according to the supply wire’s maximum

amperage rating.

4. Calibration: Periodic recalibration of DMS-20RM voltmeters is not

required under normal, indoor operating environments. If calibration is

necessary, it should only be performed by qualified technical personnel.

Calibration is performed with potentially lethal voltages applied to the

DMS-20RM and its associated wiring. A plastic, fully-insulated adjust-

ing tool must be used to access the recessed calibration potentiometer

located on the back of the unit (see Mechanical Specifications). Contact

Murata Power Solutions if additional information is required regarding

calibration, setup, or any other technical issue pertaining to DMS-20RM

ac voltmeters.

ORDERING INFORMATION

DMS-20RM-1-AC1-R-C

0 to 19.99Vac, AC Powered

DMS-20RM-2-AC1-R-C

0 to 199.9Vac, AC Powered

DMS-20RM-3-AC1-R-C

0 to 300Vac, AC Powered

DMS-20RM-1-DC2-R-C

0 to 19.99Vac, DC Powered

DMS-20RM-2-DC2-R-C

0 to 199.9Vac, DC Powered

DMS-20RM-3-DC2-R-C

0 to 300Vac, DC Powered

Performance/Functional Specifications

Typical at TA=+ 25ºC with 60Hz sine-wave input, unless otherwise noted

Full-Scale Input Voltage (TB2)

Min.

Typ.

Max.

Units

DMS-20RM-1

DMS-20RM-2

DMS-20RM-3

0

0

0

—

—

—

19.99

199.9

300

Vac

Vac

Vac

Frequency Range

47

60

1000

Hz

Performance

Sampling Rate

2.5 reading per second

Accuracy

➀

±0.4%FS ±2 counts

with 60Hz sine wave input

Measurement Type

rms responding, Crest Factors of 1-5

Temperature Drift (0 to 60ºC)

±0.2

±0.4

Counts/ºC

Zero-Volt Reading (within 30 sec.)

-001

000

001

Counts

Breakdown Voltage, TB1 to TB2

2000

—

—

Vdc

Power Supply Voltage (TB1)

DMS-20RM-X-AC1

85

—

264

Vac/47-63Hz

DMS-20RM-X-DC2

+10.0

—

+40.0

Vdc

Power Supply Current (TB1,

➁)

DMS-20RM-X-AC1

—

30

50

mA/47-63Hz

DMS-20RM-X-DC2

—

10

15

mAdc

Terminal Block Wiring (TB1 and TB2)

Wire Size

16-22AWG, Solid or stranded

Insulation Strip Length

0.250 inches

Screw Tightening Torque

3.6 pound-inches (0.4Nm)

Rated Voltage

300Vac

Display

Display Type and Size

3½ Digit LED, 0.37”/9.4mm high

Overrange Indication

“1___”

Decimal Point

Fixed, model dependent (see full-scale input

voltage above)

Physical/Environmental

Operating Temperature

-25

—

+60

ºC

Storage Temperature

-40

—

+75

ºC

Humidity (non-condensing)

0

—

85

%

Dimensions

Model dependent; see product datasheet.

Weight:

1.3 Ounces (36 grams) nominal

➀ Specified 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. Voltmeters are calibrated

with a near full-scale, 60Hz sine-wave input.

➁ Specified maximum power supply currents are steady state; larger surge currents can occur at

initial application of power.