Voltage Divider Self-calibration Method for Embedded Systems

作者： GOZ Electric 时间：2024-11-07 09:23:11 阅读：45

As an important voltage ratio device, high-precision binary resistor dividers are widely used in measurement and calibration, electrical measuring instruments and other fields. Since the working current of DC resistor dividers is usually very small, generally below 1MA, the temperature change caused by resistor heating is less affected, and the voltage divider can achieve high accuracy and stability. It is often used to accurately and stably measure voltage waveforms and test and calibrate high-sensitivity DC microvolt meters. With the rapid development of high-performance analog-to-digital converters and digital-to-analog converters, high-precision resistor dividers have also been widely used in the linearity verification and evaluation of high-performance ADCs and DACs. Therefore, the development of a high-precision resistor divider that can simply and quickly achieve ratio self-calibration has important application value. Traditional multi-stage resistor dividers are expensive, complex in structure, and have a complex and time-consuming calibration process. They are difficult to meet the demand for low-cost, high-performance resistor dividers in the field of test and measurement. Based on the binary resistor voltage divider structure and combined with embedded systems, this paper designs and implements an automatically calibrated binary resistor voltage divider. The binary resistor voltage divider has a simple structure and is easy to implement. Through the reasonable layout and selection of key components such as switches and resistors involved in the resistor voltage divider, it is relatively easy to achieve high stability and high accuracy of the voltage divider. At the same time, the embedded system can easily simplify, automate and efficiently implement the calibration process.

1 Experimental principle

Resistor voltage divider and ratio self-calibration principle

The principle of the eight-bit binary resistor voltage divider is shown in the figure. All the resistors in the figure have the same nominal value. A double-pole double-throw switch is used to exchange the voltage drop resistor and load resistor of each level. A single-pole double-throw switch is used to provide a reference voltage for each level of self-calibration. Ignoring the switch and wiring resistance, N pairs of measurements can be performed to fully calibrate an N-bit voltage divider.

2 Calibration system composition

Based on the principles described above, this paper designs two sets of eight-bit self-calibrated binary resistor voltage dividers. The actual picture of the resistor voltage divider is shown in the figure. In the figure, the left side is the embedded system control circuit, and the right side is the voltage divider network, which is mainly composed of relays and resistors.

The block diagram of the calibration system is shown in the figure, and the actual diagram of the calibration system is shown in the figure. The calibration system consists of a ±10V source, two sets of self-calibration binary resistor dividers, a digital voltmeter, a microprocessor and a computer. The control system. Among them, the two eight-bit binary resistor dividers are completely independent and passive. The self-calibration process is that the computer sends control instructions to the microcontroller through RS232, the relay drive circuit realizes the switch switching, and the digital voltmeter feeds back the measurement results to the computer through the GPIB bus. Finally, the microprocessor analyzes and calculates the data. The entire calibration process takes about a few minutes and can achieve higher accuracy.

This paper designs and implements a high-precision binary resistor divider based on an embedded system. This voltage divider has a simple structure, higher accuracy and can realize automatic ratio self-calibration compared to the existing high-precision resistor divider. The self-calibration method provided in this paper can be completed in a few minutes, solving the problems of complex and time-consuming calibration process of existing equipment. The voltage divider provides a voltage divider ratio accuracy that exceeds that of existing instruments and provides a reliable compensation reference for regular calibration and correction of existing equipment. To verify the reliability of the voltage divider and the self-calibration method, two independent eight-bit binary voltage dividers were developed. The experimental results show that the relative deviation of the ratio calibration is less than 5×10(-7). This deviation is mainly caused by the short-term stability of the precision resistors used in the voltage divider. The accuracy of the ratio calibration can be further improved by using resistors with higher stability. At the same time, the compensation parameters of the voltage divider after self-calibration can be corrected by adding a digital-to-analog conversion module to achieve a voltage divider ratio output that is closer to the nominal value.