Research And Design Of Electromagnetic Current Meter Based On Boron Doped Diamond Thin Film

As one of the important parameters in ocean hydrology,the measurement and recording of the speed and direction of ocean currents are of great significance to marine aquaculture,shipping,marine environmental protection.Compared with other current meters,electromagnetic current meters have the advantages of no mechanical wear and good robustness.However,compared with foreign-made electromagnetic current meters,domestically-made ones still have shortcomings such as low measurement accuracy and poor long-term stability.To address the aforementioned issues,this thesis uses boron-doped diamond(BDD)electrodes as replacements for traditional electrodes to enhance the long-term stability of the electromagnetic current meter.Various functional module circuits are designed with lock-in amplification technology as the core,aiming to improve measurement accuracy.Additionally,electrode encapsulation casing assembly and software design are conducted.Finally,laboratory and onshore experiments are performed on the electromagnetic current meter,resulting in favorable outcomes.The following research work has been mainly completed in this thesis:(1)Optimization design was carried out on the electromagnetic current meter probe based on boron-doped diamond material.Using the hot filament chemical vapor deposition(HFCVD)method and metal niobium as the substrate material,boron-doped diamond thin film electrodes were prepared,and boron-doped diamond thin films with compact structure and good crystal quality were obtained.The prepared boron-doped diamond electrode was encapsulated with the electromagnetic current meter probe.(2)Hardware circuit was designed using lock-in amplification technology to modulate and process the microvolt-level ocean current electric field signal and shift it to the ultra-low noise frequency band of the current meter probe,which enabled the extraction of weak signals in high noise environments and improved the detection accuracy of the instrument.Hardware-related programs for the lower computer were written,and a user interface(UI)interaction system for the upper computer was designed to facilitate observation and operation by researchers.(3)After the assembly of the instrument,a series of tests were carried out including laboratory tank tests and shore tests.The test results showed that the boron-doped diamond film electromagnetic current meter worked stably and reliably,and the accuracy of measuring flow velocity and direction reached a good level.By innovating in electrode material and circuit design,this thesis applies boron-doped diamond thin films,which possess good stability,to electromagnetic current meters.The use of lock-in amplification technology enhances the identification and processing capability of weak signals,thus improving the stability and accuracy of data measurement of the electromagnetic current meter in marine environments.This provides some technical support for the domestication of high-reliability and high-precision electromagnetic current meters.