Why do some sensors require both positive and negative power supplies?

The main reason for choosing dual power supplies for sensors is to meet the requirements of signal integrity, circuit operating conditions, and measurement accuracy. This includes the following aspects:

1. Handling bidirectional signals (AC signals)

Some sensors (such as vibration, sound, and acceleration sensors) output signals that are bidirectional, meaning they fluctuate above and below the zero reference point (positive and negative voltages). If only a single power supply is used, the negative half-cycle signal will be truncated, resulting in distortion. At this time, using positive and negative power supplies (such as ±5V, ±12V) to provide symmetrical voltages enables the signal to fluctuate centered at 0V, retaining the complete information of the positive and negative halves to avoid signal distortion.

2. Internal circuit operation requirements

Many sensors integrate operational amplifiers or analog circuits for signal amplification or processing within their internal circuits. These devices require positive and negative power supplies to achieve:

Simplified circuit design: In a single power supply system, when processing AC signals, a "virtual ground" needs to be set, which introduces additional noise and design complexity. While positive and negative power supplies naturally use "ground" (0V) as the reference point, without the need for additional bias circuits, this simplifies the design and reduces noise.

Maximizing dynamic range: Many high-performance sensors and operational amplifiers require dual power supplies to fully utilize their input/output range, avoid non-linear distortion, and improve the linearity and dynamic range of the system.

3. Anti-interference and noise suppression

The dual power supply design can reduce common-mode noise interference. Common-mode noise refers to the voltage difference between two signal lines to ground. Using positive and negative power supplies can effectively reduce this voltage difference, thereby reducing common-mode noise interference, especially in industrial environments, symmetrical power supply helps to improve the signal's signal-to-noise ratio.

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