Study on the Communication between Single Parameter Profilometer and PC

With the rapid development of industrial technology, the requirements to surface feature of machinery parts are more and more high. It is far not enough to describe the machined surface feature with single roughness parameter Ra, but the instrument improvement for adding measurable roughness parameters is always companied with the cost increase. Therefore, how to acquire multi-parameter measurement of machined surface feature with existing single parameter profilometer is a significant and practical problem. It is a convenient and efficient way to acquire measurement data through the communication between measurement instrument and personal computer through parallel printer interface. This paper investigates the feasibility. A portable profilometer was taken as the displacement sensor, which was communicated with PC through parallel printer interface under the control of special software written by ourselves. The plentiful information of measured surface was entered the computer, through data processing the surface profile curve and various parameters were produced automatically. Consequently, the surface feature can be fully investigated. Introduction In the drastically international market competition, product quality is the strongest weapon by which enterprises win the competition. A lot of enterprises, especially small and medium-sized enterprises still acquire and process information manually in part manufacturing and quality controlling, which is time-consuming and easy to make mistakes, also difficult to set up effective information feedback system in time. The development of computer and measurement technologies make the automation of acquiring, transferring, analyzing and processing quality information possible. Machined surface roughness is an important consideration in the manufacture of parts; it has a significant effect on parts’ appliance capabilities such as wear resistance, corrosion resistance, fatigue strength, as well fitting between parts. It is necessary to design, measure and control machinery parts’ surface roughness so that the parts can meet a certain requirements. At present, there are several methods of measuring surface roughness, among them one applied widely is to use stylus instruments [1-2]. Though large or table-measuring instruments controlled by computer have already been applied in laboratories of research institutes and quality inspection departments of factories, on the working spot, particularly in the workshops of medium-sized or small factories, portable profilometer which can only measure single parameter of roughness is still used widely. Single parameter is clearly not enough to describe the features of measured surface. Therefore, it is quite practical to achieve multi-parameters which can indicate the feature of machined surface by means of single parameter profilometer. What this paper introduces is how to collect signals from the placement sensor of portable profilometer through computer parallel printer port, then analyze and calculate these signals in terms of computer data processing, finally print multi-parameters measurements This kind of method is also suitable for communicating between computer and those instruments measuring other analog quantities such as temperature, force, etc.. Output Signals of the Profilometer Key Engineering Materials Online: 2004-03-15 ISSN: 1662-9795, Vols. 259-260, pp 687-691 doi:10.4028/www.scientific.net/KEM.259-260.687 © 2004 Trans Tech Publications Ltd, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific.net. (Semanticscholar.org-13/03/20,19:03:50) 688 Advances in Grinding and Abrasive Processes Common surface profilometers are two-dimensional surface roughness surveying instruments. The operation principle of portable profilometer is as Fig.1 shows. When the sharp stylus is driven to slide directly on the measured surface, it will be up and down with the micro asperity of measured surface. The placement signal is transformed by sensor into faint voltage signal, through amplifying, filtrating and integrating circuit, then the parameter value of roughness is shown by an indicator [1]. Although this kind of instrument is quite small and convenient to use, its shortcomings are very obvious: single measurement parameter, low measurement precision, limited measurement range, inflexible measurement way (such as the choosing of assessing length, the selection of filter and so on), and can not record the measurement result and print the graph. Fig.1 Operating principle of portable profilometer From the operation principle of this kind of instrument, it is known that, when the stylus slides directly on the measured surface, in fact, as long as the stylus is sharp enough, the measured surface’s asperity information collected by the placement sensor ought to be quite abundant. However, the sequent treatment circuits only pick-up a part of the information, and depend on it to show the calculation result of the single parameter. That is to say, the sequent treatment circuits don’t make the best of the abundant collected information. So, in order to make good use of the traditional instrument for surface roughness measurement and overcome its shortcoming, computer’s strong function on information process can be use to improve this kind of instruments. As shown in Fig.2, the analog signal from the commuting circuit is amplified, then, through potential and analog/digital conversion, is entered into computer. After the datum is processed by software, the computer will print the calculation results and corresponding figures automatically on screen or printer. Parallel Port Communication of Computer With the rapid development of computer technology, conventional instruments for measuring various analogue quantities are being replaced gradually by digital instrument controlled by microcomputer or microprocessor. In process controlling and various measurements, personal computer also can control various sensors to acquire and process data quickly. The common method of connecting peripheral hardware to PC is using plug-in interface circuitry board. That is, making a data acquisition card which is connected to peripheral adapter by special cable, and plugging it in the PC’s bus. In this method the special plug-in card is rather expensive, and the host has to be opened for inserting the card in the bus expansion slot. What’s more, it needs skillful programmer to program the card. It is very obvious that the method not only increases the cost but also is inconvenient. Even, the host of portable PC or notebook computer has no built-in ISA extending slot. Besides the above way, PC can communicate with measurement instrument by own parallel or serial port. If by RS-232C, the speed of collecting data will be limited greatly (the max transmission speed is 20 kbit/s in its original criterion). However, the communication speed of parallel port is much faster than that of serial port. Parallel port, working as the host’s communication interface connected with peripheral equipments such as disk system, CD player, LAN adapter, printer and so on, is use widely in all PCs and its compatible computers. Utilizing parallel port LPT to collect information, what we have to do Sensor Driving box Amplifier commutating Filter Average Table Amplifier Integrator Integration Traverse Controller Zero Indicator Power Amplifier Recorder Ra 688 Advances in Grinding and Abrasive Processes