A High-Quality Ratio-Metric Measurement Method Based on Analog-to-Digital Converter for Precision Sensors

In this article, we propose a high-quality ratio-metric measurement (HQRM) method based on an analog-to-digital converter (ADC) for high-precision sensors, which shows significant improvement in resolution and stability as well as the sensor's ability to adapt to rapidly changing experimental environments. The traditional ratio-metric measurement (TRM) method based on ADC is introduced in detail for comparison. Circuits of the two ratio-metric measurement methods are designed and tested, and the experimental results show that the HQRM has much better suppression capability to the output noise and drift caused by the excitation source compared with the TRM. A precision capacitive displacement sensor with two ratio-metric methods is tested as an example, and it is found that the sensor's output noise and drift caused by the excitation source are significantly better suppressed with the HQRM in the full bandwidth range and the full-scale range, so the resolution of the sensor is improved from 3.79 nm(rms) to 1.51 nm(rms), and the temperature drift is reduced from 0.75 nm/°C to nearly zero even with drastic temperature changes. Furthermore, this method is expected to function efficiently for other amplitude-modulated types of high-precision sensors.