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Review of Product Offering for Battery
Current Measurement
There are three basic models of shunt resistor qualified by
Bourns for automotive applications. Table 1 outlines the key
characteristics of these models.
The resistive element in all three models has large copper
terminals as can be seen in Figure 2. Given that the resistivity
of copper is 1.72 x 10
^(-8)Ωm
and given that the resistance will
increase by 0.393% for every extra degree Centigrade in
temperature, the overall coefficient of resistance between the
two points will be higher than the resistivity of the resistor alloy
(max 50PPM/°C or 0.05%/°C).
If the distance between the two measurement points in copper
is 3mm in total as is the case with CSM2F-8536, the TCR will
increase from 50ppm/°C (TCR of element) to 150ppm/°C (TCR
of combined element plus copper terminal).
The maximum currents that these shunts can carry is quite
high. The CSM2F-7036, for example, using Ohms Law could
carry 1000A DC at a power of maximum 50 Watts. A typical
Battery Pack for a Hybrid Vehicle can be 24KWh. This is
equivalent to 500Ah in a 48V car. The currents, therefore,
especially during periods of high power such as acceleration
when moving or fast charging when stopped can be very high.
Figure 2: Block Diagram of Signal Processing Circuit and
Photo of Experiment
Key Features:
• Utilized in parallel, series,
dual-inductor, and
transformer configurations
• Magnetically shielded,
low radiation
• Inductance range of 8.2µH
to 600µH
Key Features:
• Standoff Voltage: 12V to 58V
• -55°C to +150°C operating/
storage temperature range
• Peak Forward Surge Current: 50A
SRF0703A Dual-Winding Shielded
Power Inductors
SMF4L-Q Transient Voltage
Suppressor Diodes
mouser.com/new/bourns/bourns-srf0703A/
mouser.com/new/bourns/bourns-smf4l-q-diodes/
Key Features:
• Low thermal EMF
(as low as 0.25μV/K)
• 10Nm maximum
fastening torque
• Low resistance
(as low as 50μΩ)
Model CSM2F High Power
Current Sense Resistors
mouser.com/new/bourns/bourns-csm2f-resistors/
