Acquisition Module Design And Implementation Of Broadband High Precision Oscillographuc Power Analyzer

With the continuous development of the electronics industry,more and more occasi ons require simultaneous measurement of power and transient signals.Traditional oscill oscopes and power analyzers can only meet a single functional requirement,and oscillo graphic power analyzers have emerged.The oscillographic power analyzer produced by Yokogawa in Japan has a bandwidth of 20 MHz,but its accuracy is only 0.1%,which ca nnot meet the current demand for high precision.The oscillographic power analysis acq uisition module designed in this paper has a maximum accuracy of 0.02%FS.The oscill oscope power analyzer brings a new style of high-precision measurement.The main research content of this article is around the two key indicators of lenienc y and high precision,which can be divided into the following three parts :1.Acquisition circuit design.Aiming at the requirements of broadband and high precision,a large voltage and high current acquisition circuit is designed to meet the requirement.The key of the voltage acquisition circuit is three requiments of large voltage,broadband and high precision;For the large voltage,a resistance voltage division acquisition mode is designed;For broadband and high accuracy,different resistance voltage division methods are compared and a resistance-capacitor is selected and designed.The voltage divider circuit solves the problems of large capacitor errors by designing of exquisite res-cap matching mathods,and solve the impact of distributed capacitance on the voltage divider network by optimizing the design of PCB grounding and routing.While current sampling are meeting the same problems with the voltage sampling,it also faces the problem of high-power heating.After comparing four different current samplingmethods,the resistor series sampling method is selected;The sampling resistor that meets the requirements of accuracy and dissipation is selected;For the highside current sampling CMRR problems,a differential circuit with high CMRR is designed;For thermal issues,PCB copper and traces are analyzed and designed in detail.2 Gain conditioning circuit design.Band width and high precision are often two contradictory parameter.This design designed a low-noise and high-accuracy gain circuit under the conditions of bandwidth.Based on the system’s requirements,the ADC requirements are analyzed,and ADC that meets indicators are selected and designed.Design the low delay drive circuit to ensure normal operation of ADC.Finally,for the system bandwidth and high-precision indicator,the composition and source of the noise of the sampling module are analyzed.According to the analysis of the noise composition of the op amp,the low voltage noise op amp and the smallest possible feeback resistor are used to reduce the single op amp circuit’s noise.According to yhe analysis of the overall noise superposition and transfer of the module,the low noise device is placed in front of the module and a large gain is set to reduce the overall noise level of the module.At last,simulation and calculation show that the equivalent input noise of the sampling module is only 25.06μV,and the input noise of the sampling module completely meets the high-precision indexes of the system.3.Universal circuit design.There are many circuits in the acquisition module that have little to do with the accuracy of the acquisition module,but are closely related to the function implementation and normal operation of the system.Design a protection circuit to ensure that the module is not damaged when a large voltage or large current is input in a small range;A filter circuit is designed to meet the filtering requirements in the actual measurement of the instrument;A frequency measurement circuit is designed to implement the system’s wideband frequency measurement function.In order to meet the system’s high isolation requirements,a signal isolation and power isolation circuit sidesigned;The power requirements of the sampling module and power noise are analyzed,and power supply system is designed to meet the module the module’s power requirements while meeting the module’s low noise requirements.In the end,the test results show that the function and indicators and indicator of the analog channels meet the expected design goals.