OCT Signal Processing System Based On Auto-Balance Method

The Optical Current Transducer based on Faraday Magnetic-optical Effect overcomes the shortcomings of the electromagnetic CT, have broad dynamic measurement and frequency response range, which can not only be used for measuring the AC signals, the harmonic signals and direct flow, but also can repeat the transient signals with High Fidelity and have good dynamic response capability. The research on data processing methods for OCT is one of the important contents. An appropriate data processing method can eliminate the effect of interference factors.The difference signal processing method of optical current transducer is carried out in this paper. It is indicated that the realization of the difference signal processing method requires the high coherence of the parameters of the measurement branches. Furthermore if it is realized totally by software it has the defects of the big quantizing error, low resolution and large amount of calculation quantity.For the problem of low resolution, a new method named"Auto-Balance Difference Signal Processing Method"is put forward. This method combines the software and the hardware together, before the signal collection using the hardware to eliminate the static working light intensity component of the measured signal, and then amplify the remnant measured component, which resolves the question of low resolution. For the parameter changes caused by the environment factors, the feedback control linked by the MCU and programmable amplifier is imported, it automatically adjusts the balance of the two branch parameters, acquires the measured component in the condition of the two branch unbalance parameters. Considering the large amount of calculation problems caused by the division operation for removing light intensity fluctuations, the method that the static working light intensity for the AD transform references is presented. It introduce uses the nature of AD transform as division operation, reduces the original method of the two division operation, greatly decreases the amount of computation and improves the measurement accuracy.Based on this"Auto-balance difference method"the signal processing systems for OCT is re-designed. The data acquisition circuit uses the ADμC812 chip to design programs for acquired data by DAC port for controlling programmable gain. Therefore fast and accurate data acquisition and delivery are realized. The entire system increases the effective median signal of AD converter and improves the measurement accuracy, which is beneficial for product-grade OCT and digitalization of the substation.Debug and test is made on the performance of various functional modules of the designed signal processing systems. Testing results show that technical indicators of the system satisfy the expected design requirements and achieve the designed goal.