Abstract: A novel shaft angle/digital conversion circuit for a rotary transformer is presented. A rotary transformer shaft angle/digital conversion system was constructed using an NI PXI-6070E multi-function digital acquisition card, PXI bus, a general-purpose computer, and the LabVIEW graphical programming language. MATLAB simulation shows that the system meets the required accuracy. This data acquisition and processing system based on virtual instrument technology features high cost-effectiveness, short development cycle, and ease of integration and expansion, and has certain application value. Keywords: resolver R/D conversion; data acquisition; virtual instrument; simulation [Abstract] A new circuit of resolver R/D conversion is presented, and the circuit is composed of NI PXI-6070E multi-functional DAQ board, PXI bus, PC and LabVIEW. By simulating in MATLAB, it can be found that the system can meet the precision requirement. The Virtual-Instrument-based data acquisition and processing system is inexpensive and easy to build, integrate and extend. [Key words] resolver R/D conversion data acquisition virtual instrument simulation 0 Introduction In the platform compass, a resolver is used as the measuring element for the ship's pitch, roll and heading angular position information. The shaft angle/digital conversion technology converts the analog quantity output by the resolver into a digital quantity. The three most successful shaft angle/digital conversion circuits are the shaft angle/digital conversion circuit based on a single-chip microcomputer, the shaft angle/digital conversion circuit using the RDC17XX series module, and the shaft angle digital conversion circuit using the single-chip thin-film integrated circuit AD2S80A [1]. The three methods have their own advantages and disadvantages in terms of conversion accuracy, tracking speed, and construction and maintenance costs, and are often used in different occasions. Based on the above three traditional conversion circuits, this paper proposes a shaft angle/digital conversion circuit based on virtual instrument technology. The outstanding advantages of this circuit are that it is easy to develop and maintain, easy to expand, and low in cost, while also meeting the requirements in terms of accuracy and speed. 1 Rotary Transformer Angle Measurement Principle A rotary transformer is an AC micro motor that can output an electrical signal that has a certain functional relationship with the rotor angle or position. Among them, the sine and cosine rotary transformer is a widely used one [2]. In order to improve the angle measurement accuracy, the method of combining coarse and fine rotary transformers is commonly used. A multi-pole rotary transformer generates a multi-pair pulsating magnetic field along the inner circumference of the stator when an AC excitation voltage is applied to one phase winding of its stator or rotor. Its working principle is exactly the same as that of a single-pole rotary transformer, except that the effective value of the output voltage changes with the rotor angle at different periods. The combination of roughing and finishing machine operations means that when the roughing machine shaft angle completes one revolution, the finishing machine shaft angle completes n revolutions (n ​​is usually 16-36, but sometimes 64). That is, the roughing machine determines the approximate position of the shaft angle, and the finishing machine obtains the precise position. Therefore, the roughing and finishing machine shaft angles need to be combined to obtain the true mechanical shaft angle. For details, please click: Research on Shaft Angle/Digital Conversion Technology Based on Virtual Instruments