Shunt Resistor vs. Hall Effect Current Sensing: A Comparison

This article compares shunt resistor current sensing and Hall Effect current sensing. It highlights the differences between the two methods and discusses their respective advantages and disadvantages.

Shunt Resistor Current Sensing

Figure 1 illustrates high-side shunt resistor-based current sensing.

Alternatively, a low-side shunt resistor configuration exists, where one resistor terminal connects to the battery ground (U1) and the other to the load. The voltage drop across the shunt resistor is directly proportional to the current (I) flowing through it.

This relationship can be expressed as:

$U2 - U1 = R_{Shunt} \times I$

…

Equation-1

The voltage difference is then amplified using an Operational Amplifier (Op-Amp) and fed to an Analog-to-Digital (A/D) converter. The resulting digital output can then be processed using a microcontroller.

Advantages and Disadvantages of Shunt Resistor Current Sensing

Advantages:

• Ease of Implementation: This method is relatively straightforward to implement.
• Versatility: Suitable for both AC and DC current measurements.

Disadvantages:

• No Galvanic Isolation: Provides no isolation between the measured circuit and the measurement circuitry.
• Voltage Drop: The voltage drop across the shunt resistor can be a significant concern.
• Power Dissipation: Power is dissipated in the shunt resistor, contributing to heat.

Hall Effect Current Sensing

Figure 2 shows a typical Hall Effect current sensing setup.

When current (I) flows through a conductor, it generates a magnetic field around the conductor. The strength of this field (H) is proportional to the current and inversely proportional to the distance (r) from the conductor. This relationship is described by the following equation:

$H = \frac{I}{2 \pi r}$

…Equation-2

The direction of the magnetic field (H) can be determined using the “right-hand rule.” The relationship between the magnetic flux density (B) and the magnetic field strength (H) is given by:

$B = \mu_0 \mu_r H$

…Equation-3

$=> B = \mu_0 \mu_r \frac{I}{2 \pi r}$

Where:

• $\mu_0 = 4\pi \times 10^{-7}$ is the permeability of free space.
• $\mu_r$ is the relative permeability of the core material.

As shown in Figure 2, the output voltage (Vout) of the Hall Effect sensor is proportional to the generated magnetic field (B). The Hall Effect sensor IC takes Vout as input and generates a corresponding digital output, which can then be read by a microcontroller.

Advantages and Disadvantages of Hall Effect Current Sensing

Advantages:

• Galvanic Isolation: Provides electrical isolation between the measured circuit and the measurement circuitry.
• No Voltage Loss: Does not introduce a voltage drop in the measured circuit.
• Versatility: Suitable for both AC and DC current measurements.

Disadvantages:

• Cost: The cost of the field concentrator can be a concern.