Exploring DIY Hall Sensors: Unleashing Creativity and Satisfaction
Crafting your own Hall sensor can be a fascinating and fulfilling endeavor, far more engaging than purchasing pre-made ones. The key lies in utilizing a touch layer with utmost thinness, rendering the length and width inconsequential. A logical starting point for experimentation is copper, widely available in the form of printed circuit board material and easy to work with. Although copperclad boards are an apparent choice, they are suboptimal due to their weak Hall constant. Despite this limitation, they can serve our purpose by demonstrating the Hall effect when paired with exceptionally powerful magnets in our sensor experiments.
Maximizing Amplification for Detection: Circuit Configuration and Precision Adjustment
In the pursuit of achieving precise detection, the primary goal is to attain the highest level of amplification possible. The circuit depicted in this setup relies on the relationship between the two feedback resistors of the first opamp to establish voltage amplification. With the specified values of 2.2 MΩ and 330 Ω, an impressive gain of 6,667 is achieved. Additionally, this configuration offers a practical bridge connection for conducting measurements. A trimmer potentiometer is incorporated, enabling meticulous adjustments. With a precise zero setting accurate to within millivolts, this test point becomes invaluable for measuring Hall voltages, even at levels significantly below a microvolt. Furthermore, this method allows for the measurement of a magnet’s flux density with precision.
Copper has a Hall constant of AH = –5.3·10- 11 m3/C. The thickness of the copper layer is d = 35 µm. The Hall voltage then amounts to:
VH = AH × I × B / d
Optimizing Sensitivity: Challenges and Precision in Hall Voltage Measurements
In scenarios where the magnetic field strength (B) equals 1 T and the current (I) equals 1 A, a Hall voltage (VH) of 1.5 µV is generated. Through a remarkable 6,667-fold gain, this translates into a substantial figure of 10 mV. Consequently, the circuit demonstrates a sensitivity of 10 mV per Tesla. However, fine-tuning the zero point using P1 proves to be a challenging task. The amplifier operates with a distinct power source provided by a 9 V battery (BT1). To initiate measurements, the Hall sensor (the copper surface) is connected to a lab power supply with adjustable output current (BT2), ensuring a precisely controlled current flow of 1 A through the sensor. At this point, recalibrating the zero point becomes imperative.
Moving forward, positioning a potent Neodymium magnet beneath the sensor triggers a notable fluctuation in the circuit’s output voltage, varying effectively by several millivolts. It’s essential to acknowledge various factors that influence our measurements. Any displacement of the magnet induces a voltage in the power feed wires, surpassing the Hall voltage itself. Consequently, allowing time for measurements to stabilize after each movement is crucial. Furthermore, when dealing with such minute voltage measurements, issues may arise due to thermal voltages caused by temperature fluctuations. To obtain accurate results, remaining as still as possible and minimizing any movement is essential—requiring patience and precise control over environmental factors.