给出了光纤电流传感器的数学模型,推导出了传感器测量准确度的数学表达式,并对系统的主要特征参数进行了分析。提出了一种在线监测方法,将环路增益值解调并实时输出,作为传感器系统的一个故障监测点。然后在此基础上,提出了环路增益稳定控制技术,使环路增益能够实现自动调整,消除了系统在长期运行时因环路增益变化对精度的影响。实验结果表明:改变前置放大器的放大倍数,在线监测的环路增益值、比值误差和相位误差均随之改变,实验结果与仿真结果一致;引入环路增益稳定控制技术后,改变前置放大器的放大倍数,在线监测的环路增益基本保持不变,且传感器的比值误差和相位误差波动也在准确度范围之内,验证了在线监测方法和环路增益稳定控制技术的有效性。

We develop a mathematical model of a fiber optic current sensor and deduce a mathematic equation of measurement accuracy of the sensor. The influence of the loop gain variation on the measurement accuracy is theoretically investigated. Further, we develop a method for online monitoring of the loop gain. The loop gain value is demodulated and transmitted to the monitor in real-time as one of fault monitoring points for system monitoring. A stable loop gain controlling technique is developed to automatically adjust the loop gain, thereby eliminating the accuracy degradation caused by the loop gain change in the long-time system running. Results show that loop gain value monitored online as well as the scale factor error and phase error change as the preamplifier gain changes, consistent with the simulation results. Furthermore, the loop gain value monitored online remains stable, and appropriate measurement accuracy can be achieved while utilizing the proposed stable controlling technique. These observations denote the effectiveness of the proposed online monitoring and stable controlling technique for loop gain.