Research And Design Of High Precision Phasemeter And GPIM Interface

This paper is based on the program of the development of high pricison and largebandwidth phasemeter which provided by TianJin zhonghuan electronic limited company. Thetechnologe of phase measurement now has been deep into many industrial fields, especially inthe areas of electronics, power systems, industrial automation, intelligient control andavionics have a wide range of applications. Currently a few companies and institutes havesome devices delicatied in phase measurement, but these phasemeters always have someproblems such as the response time is slowly, the accuracy is low and the requirements aboutamplitude and frequency of mensured signal is too high. In order to solve these problems, thispaper has degined a high-performance and high-pricison phasemeter. The important contentof this paper is divided into the following four parts.1. Reserch of phase measurement methods. The article fist has analyzed the phasemeasurement techniques in the world, and introduces three methods about phase measurementmethods, they are oscilloscope observation, digital phase measurements and zero phasemeasurements. Finally this paper chooses zero phase measurements as the theory of design ofhighe precision phasemeter.2. Design of auto-range circuit. The circuit mainly concludes attenuation network,amplifier circuit, leval dectection circuit and logic control circuit. This circuit uses theprinciples of the cycle counting method, by controlling the relay switch to achieve varyingdegrees of amplification and attenuation. This circuit effectively makes the phasemeter systemsafer.3. Achievement of zero-phase hardware design. According to the workflow of phasemetersystem, the system concludes shaping circuit, a phase circuit, a square wave voltage switchcircuit, A/D converter, frequency mesurement circuit and display circuit. The shaping circuitshapes the input sinusoidal singal into a square wave. The phase difference between twomeasured signals is converted into a DC voltage by the phase circuit and square wave voltageswitch circuit, and the DC voltage is proportional to phase difference. Frequencymeasurement circuit can simultaneously display the current input of the signal frequency4. Design of GPIB interface. GPIB interface is configured by the programmablephasemeter meets the intelligent needs of high-precision phasemeter. This article firstdescribes GPIB bus and IEEE488protocol briefly, and then introduces the GPIB bus datatransfer mechanism and ten GPIB interface functions. Some interface functions such as listen,talking and serial poll are achieved by accessing to internal register of NAT9914bymicrocontroller STC89C52, it meets communication needs between phasemeter andprogrammable computer.The results shows that the amplitude of input signal of the high precision phasemete designed by this paper can be up to320V, and the signal bandwidth is5MHz, the phasemeterresolution is0.1°, the accuracy can reach0.1°. In addition, GPIB interface has good stabilityand data transmission capability.