In the technical fields of precision angular displacement measurement, in recent years, a new type of time-grating sensor has been developed in China. This time-grating sensor uses a clock pulse as the reference for displacement measurements. And based on the foregoing, a time-grating angular displacement sensor based on alternating electric field has been further developed. The patent application document for this sensor has been published on Apr. 25, 2012 with its Title of Invention as “Time-grating angular displacement sensors based on alternating electric field” and patent number: CN102425987A.
The foregoing time-grating angular displacement sensors based on alternating electric field has adopted a differential capacitance with a single layer structure as its signal coupling channel. In addition, two channels of standing wave signals have been induced by two circles of electrodes, and then the two channels of standing wave signals are combined into one channels of traveling wave signal by an adding circuit. However, due to the reason that the length-width ratios of the two circles of electrodes disposed at cylindrical end surface are not the same, and accordingly the varying patterns of the corresponding two channels of standing wave signals are not the same as well, the signals of the two circles of electrodes may interfere with each other, which could lead to an increase of measurement errors, and thus hinder further improvements in its measurement precision. On the other hand, concerning its manufacturing process, it is difficult to ensure a consistency between the two circles of electrodes; in addition, concerning its installation, it is difficult to ensure the consistent of electric field coupling strengths between the two circles of electrodes as well. As a result, the foregoing issues may result in an inconsistency in amplitude of the generated two channels of standing wave signals, which will lead to measurement errors and thus compromise its applications in industrial field.
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