Performance/Functional Specifications
Typical at TA = +25ºC , V+ = 12 VDC unless otherwise specified
ORDERING INFORMATION
DCM20-1-DC5-R-C (Red Display)
DCM20-1-DC5-G-C* (Green Display)
DCM20-1-DC5-B-C* (Blue Display)
*Consult factory for availability
TECHNICAL NOTES
IMPORTANT! To ensure safe and reliable operation, DCM20 power
meters must be installed and serviced by qualified technical personnel.
Contact Murata Power Solutions if there is any doubt regarding their
installation or operation.
1. Measurement Type: DCM20 series multifunction DC power meters
employ precision ADCs and a low-power microcontroller to measure and
display DC voltage, current and power. The choice of measurement is
selectable through the front panel. The meters measure DC current using
an external series shunt resistor which is inserted into the circuit to be
measured. Because the DCM20 has a wide common-mode input range
(0 - 72 VDC), the shunt resistor may be inserted into either the high-side
(supply) or the low-side (return) of the circuit being monitored.
DC Voltage may be monitored either at the meter’s +IN (TB1-3) input
terminal or at the meter’s +V (TB1-1) power input terminal, based on
the setting of jumper block J1. The choice of voltage monitoring input is
selected based on the application requirements.
The DCM20 derives its DC power measurement by multiplying the
measured current by the measured voltage. Power is always reported
as a positive quantity, regardless of the polarity of the measured current.
(Power = | Voltage × Current | ).
2. Basic Operation: Upon first application of power to the meter, the unit
will first perform a self-test routine and then continuously display DC
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 twice in succession will cycle the display to AMPS,
and then to WATTS (or kW, depending on the power measurement value).
Momentarily touching ‘SEL’ a third time will return the display back to
the VOLTS reading mode. Holding the ‘SEL’ button down for 5 seconds
will place the unit in a continuous auto-cycling mode, and the display will
repetitively scroll through all three measurements, with each measure-
ment 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. Momentarily
touching the ‘SEL’ button again will cause the unit to briefly display ‘Auto
OFF’ before it returns to the fixed VOLTS reading mode.
The power-up default display mode (Volts/Amps/Watts/Auto-cycle) may
be selected by simply leaving the DCM20 in a given display mode for 60
seconds or more. The next time the meter powers up, it will do so in the
new default mode. The default mode may be reset by selecting a new
operating mode and leaving the meter in that mode for 60 seconds or
longer.
3. Calibration: The DCM20’s voltage measurement function is factory-
calibrated and cannot be field-calibrated. Because the meter is designed
to work with a wide range of shunt resistors for current measurement,
however, field configuration and fine adjustment of the current measure-
ment function is supported. The DCM20’s shunt scaling factor is selected
by a 4-position DIP switch SW1 on the rear of the unit (refer to figure 9,
Mechanical Specifications). A total of 16 ranges are supported. Table 1
lists supported current ranges and their associated switch settings, and
also includes recommended Murata shunt resistors for selected ranges.
Additionally, a trimmer potentiometer on the rear of the unit supports fine
adjustment of the shunt scaling factor to accommodate tolerance errors
!
Measurement Limits Min Typ Max Units
DC Voltage
(A) 0.5 V 72 V DC
DC Current
(B)
Range ‘1’ - 10 mΩ external shunt
Range ‘16’ – 41.67 µΩ external shunt
-5
-1200
5
1200
A DC
Current Shunt Differential Voltage
Range
(C)
-100 +100 mV DC
Current Shunt Common-mode Voltage
Range
(D)
0 72 V
Current Fine Trim Range using Trim
Potentiometer
±1%
Power
Watts Display Mode
Kilowatts Display Mode
0
0
9999
96
W DC
kW DC
Performance
Display Update Rate 2.5 updates/sec.
Voltage Accuracy ± 1% ± 2%
% Full-
scale
Current Accuracy ± 2% ± 3%
Power Accuracy ± 2% ± 3%
Temperature Drift (0 - 60) +/- 0.5 Counts/°C
Zero Current Reading (within 1 sec.) +/- 4 Count
Operating Supply Voltage 9 72 V DC
Operating Supply Current
(E)
12 V operation
72 V operation
6
2
10
5
mA
Display
Display Type and Size
4 Digit LED, 9.14 mm (0.36 in) Height
4 LED Annunciators (‘Volts,’ ‘Amps,’
‘Watts,’ ‘kW’)
Over-range Indication Flashing Display
Decimal Point Selection Automatically Set
TB1 Terminal Block
Wire Size
Copper Wire
14-24 AWG
Insulation Strip Length 6mm (0.24 in)
Screw Tightening Torque 4.6 in - lb (0.51 N-m)
Physical/Environmental
Operating Temperature 0 +60 °C
Storage Temperature -40 +75 °C
Humidity (non-condensing) 0 85 %
Dimensions See figure 6
Weight
Unit Weight: 1.02 oz / 29g
Net Package Weight: 12.28 oz / 348g
Gross Package Weight: 22.05 oz / 625g
Hex Nut Tightening Torque 20 in - oz (0.14 N-m)
(A) Voltage measured across +V (TB1-1) and –V (TB1-2) OR +IN (TB1-3) and –V (TB1-2) terminals.
(B) Current measurement range dependent on external shunt selection.
(C)
Applied to +IN (TB1-3) and –IN (TB1-4) terminals.
(D)
Voltage applied across +IN (TB1-3) and –V (TB1-2) terminals.
(E)
Current drawn by +V (TB1-1) terminal when operating voltage applied across +V (TB1-1) and
–V (TB1-2) terminals.
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DCM20 Series
Three-Function DC Power Meters
MPM_DCM20Series.A01.D5 Page 2 of 6
