MPM_DMS Accessories.C01 Page 1 of 4
DMS Accessories
50mV and 100mV Base-mounted DC Shunts
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Murata Power Solutions’ 50mV and 100mV base-mounted current shunts
are designed for measuring dc currents from 5A to 1200A. These preci-
sion shunts (+/–0.25% accuracy) connect directly to MPS’s DCA5-20PC
Series of dc ammeters. Installation is straightforward: simply connect the
load circuit to the shunt’s threaded studs and the shunt’s mV Kelvin-
outputs to the digital ammeter’s input terminals.
All models feature a rugged phenolic base that provides 750V isolation
to the shunt’s brass terminals, allowing for direct attachment to metal
surfaces. A highly stable (+/–15ppm/°C) manganin sensing-element
provides a wide –40 to +60°C operating temperature range. Please see
the DCA5-20PC data sheet for additional ammeter-related information
and detailed connection diagrams.
General Specifi cations (All Models)
Rated Accuracy ±0.25% max.
Sensing Element Manganin
Terminal Posts/Screws Brass
Tightening Torgue See Mechanical Dimensions
Current Rating See Selection Guide
Operating Temperature –40 to + 60°C (–40 to +137°F)
Technical Notes
IMPORTANT! To ensure safe and reliable operation, dc shunts and all
associated equipment must be installed and serviced by qualifi ed
technical personnel. Never make any connections to the shunt, the
load, or the ammeter with energized power sources. Contact Murata
Power Solutions if you have any questions regarding the installation
or operation of any of our instruments and accessories.
1. Base-Mounted Shunt Precautions: DC current shunts are low value
resistors that develop a mV output when current passes through their
highly-stable manganin resistive element. Under high current, contin-
uous use operation, dc shunts will dissipate considerable power and
may undergo a signifi cant temperature rise. For example, if allowed
to operate continuously at its full rated load, a 500A/50mV shunt
dissipates 25 Watts (500A x 0.050V = 25 Watts). Therefore, whenever
possible, be sure to specify 50mV shunts due to their inherently lower
power dissipation and voltage drop.
To ensure that the manganin sensing element does not exceed 125°C
under worst case operating conditions, please read and follow the guide-
lines in the mounting and derating sections of this data sheet. Tighten
all connections on the shunt per the torque specifi cations given in the
mechanical dimensions and selection guide on page 3. Please note, the
user is responsible for selecting the correct wire sizes (gauge) and wire
type for the given application.
2. Mounting Considerations: All shunts should be mounted with their resis-
tance blades in a vertical position to allow for natural convection cooling
(see Figure 1). Forced-air cooling must be provided when vertical mounting
is impractical, or in installations where the shunt is installed in a confi ned
location. The shunt’s manganin blades must never be allowed to exceed
+125°C; doing so will cause permanent damage to the shunt.
Shunts must be installed in a manner that protects them from damage due
to thermal expansion forces produced by high- or short-circuit currents. In
most cases, shunts are weaker than their external-circuit connections, so
provisions for additional wiring-fl exibility may be required in high current
and/or high-vibration applications.
Whenever practical, all shunts should be connected in the grounded side
(normally the ‘chassis’) of the dc supply. However, these shunts must be
connected in the grounded side of the circuit when the dc supply exceeds
750 volts (the rated limit for the shunt’s phenolic insulating base). When
more than one wire is to be connected to each end of a shunt, the wires
must be evenly distributed between both terminals (see Figure 1).
Figure 1. Typical installation
LOAD
CURRENT
50mV
OUTPUT
Mount shunt on a vertical surface
50mV50A
