Study On Magnetic Ruler Embedded Permanent Magnets With Data Display Instrument

Making a periodic recording on magnetic tape by specific equipment is a traditional method of producing a magnetic ruler. This kind of magnetic ruler has the disadvantages that its magnetic field intensity is quite low and the magnetic signal is easy to attenuate. In order to get the magnetic signals, the magnetic header should be placed closely to the ruler. Because of the quite small distance between the ruler and header, the header can not avoid rubbing out the magnetic signals directly or indirectly. Magnetic ruler embedded with permanent magnetic overcomes disadvantages above and has better anti-jamming capability. This application is expected to have a good future. The main contents of the research in this dissertation are as follows:Mechanic structures of the magnetic ruler and the header are designed and the measurement principle of the device is expounded. Magnetic characteristic of the magnetic ruler is analyzed with ANSYS, which is a kind of finite element analysis software. The facts which reduce the measurement precision of the magnetic ruler are also considered.Forward section signal process circuit is designed according to the characteristics of liner Hall sensor. The highest process frequency of this circuit is computed in theory. The validity of the signal of the magnetic ruler is proved by experiment.Data display instrument with 100 subdivisions for the magnetic ruler basing on frequency discrimination is designed. The RC oscillator, band-pass filter, subdivision and counting circuit and LED drive circuit are designed for the data display instrument. The singlechip programs are completed in C51 language. Frequency discrimination circuit is simulated with Multisim software. An improved method for this data display instrument is presented.Data display instrument with A/D converter is designed. A subdivision counting method which is combined a programmable logic device based major subdivision and an A/D converter based minor subdivision is proposed. The cumulative error correction method of major and minor subdivision is discussed. The performance parameters of this instrument are analyzed according to the characteristics of the hardware. Serial interface between the data display instrument and computer is designed. User Interface of communication program is programmed on computer. Experiment has proved that the magnetic ruler with its data display instrument has high accuracy. The data display instrument also has a good performance in dealing with the signal of raster sensor and can be applied in general displacement sensors.