The Hall Effect occurs when a current-carrying metal or semiconductor is placed perpendicular to a magnetic field, resulting in a voltage difference across the material. This phenomenon is known as the Hall Effect, and the generated voltage is referred to as the Hall Voltage (UH). The formula for the Hall Voltage is:
**UH = K · Ia · B / d**
Where **K** is the Hall coefficient, **Ia** is the current passing through the material, **B** is the magnetic induction, and **d** is the thickness of the material. The sensitivity of the Hall effect is directly proportional to the strength of the applied magnetic field. While metals have relatively low Hall coefficients, semiconductors like silicon, germanium, indium arsenide, and indium antimonide exhibit much higher values, making them ideal for use in Hall elements.
Figure 1 shows the pin arrangement of the S-5711ANDL-I4T1G, a commonly used Hall sensor. Contactless sensing is becoming increasingly popular, especially in automotive applications where reliability is key. Hall sensors are favored for their simplicity and cost-effectiveness, although they suffer from issues such as nonlinearity, poor accuracy, slow response, and temperature drift. This paper focuses on methods to reduce the nonlinearity of Hall current sensors.
The S-5711A series is a high-sensitivity Hall IC developed using CMOS technology, capable of detecting changes in magnetic flux density and converting them into output voltage signals. It is often paired with magnets to detect on/off states in various devices. The S-5711ANDL-I4T1G has a wide operating temperature range (-40°C to +85°C) and high sensitivity, but its output voltage is nonlinear with respect to the magnetic field, with an absolute linearity of about 29%. An unbalanced voltage (UHe) also exists, which can affect measurement accuracy if not corrected.
The internal circuit of the S-5711ANDL-I4T1G includes components that generate a Hall voltage based on the formula:
**UH = KH · IH · B · cosθ + Ke · IH**
Where **KH** is the Hall sensitivity, **IH** is the drive current, **B** is the magnetic induction, **cosθ** is the cosine of the angle between the magnetic field and the component plane, and **Ke** is the imbalance factor. The unbalanced voltage, **Ke·IH**, is referred to as UHe, and the imbalance rate **Re** is calculated as **(UHe / UH) × 100%**, typically around ±10%.
To improve linearity and eliminate the unbalanced voltage, a correction circuit is employed. The circuit shown in Figure 4 adjusts the output by varying resistance values, allowing for better performance. Experimental results show that without correction, the linearity is 29%, but after calibration, it improves significantly to 7.6%. Curve 3 represents the optimal working state, while Curve 2 demonstrates improved linearity at the expense of reduced sensitivity, which can be compensated by amplification.
In conclusion, the design of this Hall current sensor, combined with nonlinear correction techniques, achieves high precision and good linearity. Through both theoretical analysis and experimentation, the circuit effectively eliminates the unbalanced voltage and identifies the best linear operating point, making it highly practical for real-world applications.
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