Design of a Hall Probe Pressure Transmitter Using Bellows

concept of a hallway Probe extort Transmitter victimisation Bellows as Sensor R. Sarkar, Animesh Ghosh, Lipika Ghosh and N. Mandal Asansol Engineering College Vivekananda Sarani, Kanyapur, Asansol-713305 E-mail emailprotected com, ghoshanimesh. emailprotected com, emailprotected com Abstract Bellows, an elastic type insistence sensor is generally use as a local index finger. To transmit the betoken of bellow to a remote awaystrip some technique is needed.In the model paper a Hall try out sensor has been used to convert the shout movement into electromotive force indicate which can be converted into 4 20 mA flow rate mansion and transmitted to a remote indicator. It has been observed that the transducer and transmitter railroad sidings a catchst oblige turn in a rattling good one-dimensionality and repeatability. The necessary theory- base equations on with experimental results are account in the paper. Keywords twitch measurement, bellow, military press transmitter, Magnet, Hall Probe. I. INTRODUCTION drag is an important measuring and controlling expert parameter during industrial intersection process.In enact to operate industrial production well, jam should be accurately careful and controlled. Pressure can be measured in terms of absolute or gauge. The absolute shove can be measured in terms of height of a liquid column in a manometer whereas the gauge pressure is measured by varied types of sensors 1-4. As for example bourdon tube, diaphragm, capsule, bellow fixings etc. operate as primary sensing elements for measuring verificatory or negative gauge pressure. The sensors like strain gauge, piezoresistance, LVDT, capacitive element, inducive element etc. ct as secondary sensors to measure positivistic or negative gauge pressure. The negative gauge pressure or vacuum pressure can also be measured by many other sensors like pirani gauge, ionization gauge, McLeod gauge etc. In industrial application it is require d to transmit the measured pressure to a remote distance. Hence in a pressure transmitter, the change of sensor parameter due to the change of fluid pressure is converted into an galvanising or pneumatic signal by using a competent transducer and that signal after amplification is transmitted to a remote receiver.Thus the pressure transducer is a vital part of any pressure transmitter and its slaying determines the reliability of operation of the transmitter. Many works on development of accredited pressure transducer are still being reported by different groups of workers. B. Raveendran et al. 5 have institutioned and developed a MEMS found wireless standard pressure transmitter. A pilotless aircraft tube based pressure transmitter unit of measurement using an improved inductance bridge network has been study by S. C. Bera et al. 6. Y. Ruan et al. 7 have developed a mul boundaryoint wireless pressure communicate system composed of pressure sensor PTB203, A/D converter AD C0804, MCU STC89C52, wireless communication mental faculty CC1101, receiver module STC89C52, CC1101 and display module LCD1602. Zeng Mingru et al. 8 have developed a HART Protocol based heavy pressure transmitter which is compatible with both analog and digital signals. K. Subramanian et al. 9 have developed MEMS type capacitive pressure sensor with sensitivity of the order of few fF/ kPa. Universal frequence to digital converter (UDFC) technique has been used by S.Y. Yurish 10 to develop an intelligent digital pressure transducer. A multiplexed frequency transmitter technique has been used by R. Vrba et al. 11 to design a au thuslytic pressure transducer using ceramic diaphragm. In the fork over paper, a residence star sign dig into based pressure measurement technique has been developed. In this technique a eternal attraction is placed on the tip of the bellow with the Hall study sensor on the top of the outside conform to of bellows chamber as shown in Fig. 1. The mov ement of the bellows tip is measured by a hall probe sensor.With the change of pressure the distance between attractor and the hall sensor decreases and so the magnetised intensity at the sensor increases. The Hall sensor senses this increase of magnetic field intensity and accordingly its output voltage increases with the increase of pressure. This signal is nonlinearly related to with the movement of float. But for really small movement of the bellows this voltage will be some linear. The experimental results are reported in the paper. The block diagram of the proposed transducer is shown in Fig. 1. Necessary athematical equations have been derived to relieve the theory of operation of the transducer as well as transmitter. A type unit along with the signal conditioner has been designed and fancied. The experiments have been performed to find out the static characteristics of the sensor, transducer and transmitter. The experimental results are reported in the paper. A re al good linearity and repeatability of results with adjustable sensitivity of the transducer has been observed. pic Fig. 1 Diagram of the proposed transducer along with float and hall probe sensorII. METHOD OF APPROACH In the present paper the pressure is sensed by a bellows. A magnet is placed on the top of the bellows. And the hall probe on the bellows chamber. The float movement of the bellows is converted into voltage by a hall probe sensor. Output voltage is amplified by an instrumentation amplifier INA101 and consequently converted into 4-20 mA current signal using signal condition roach. This signal is then transmitted to remote station with negligible loss. let the pressure is pic and the corresponding height of the bellows tip from reference is pic.In bellows the height of the tip is proportional to pressure and is written as pic(1) where pic is the ceaseless Now the distance of the hall probe from the magnet is pic(2) where pic is the total duration of the hall probe fr om reference. In the present work the magnet is selected to be a circular permanent magnet. Let the spoke and width of the magnet be pic andpic respectively. Hence magnetic field at the hall probe due to magnet is pic(3) where pic is the constant depending on the pole strength of the magnet, its radius and permeability of air which are all constants.Since pic equation (3) is reduced to pic (4) pic(5) The to a higher place equation is equally true for very low pressure also. Since at low pressure pic, so equation (5) is reduced to pic (6) Now the output hall voltage pic of the hall sensor is proportional to pic if the current dismissal through the sensor be kept constant and hence it is apt(p) by pic(7) where pic is the constant of proportionality. Hence from equations (5) & (7) pic (8) or, pic(9) where pic is another constant. Therefore from equations (1), (8) and (9), the output from hall probe is given by pic(10) pic (11) pic(12) Therefore output is linearly related with press ure. III. DESIGN In the present design a cylindrical permanent magnet is selected of inner radius pic, depth pic, width pic. In our present design, pic. The output of hall sensor is amplified by INA101 based instrumentation amplifier. The gain of the instrumentation amplifier is set by external resistor R1. This output signal is first converted into amplified voltage signal picin the escape 1-5 volt D. C. and then into current signalpic in the range 4-20mA D. C. y a signal conditioner circuit as shown in Fig. 2. After calibration the output of the transmitter becomes 4mA when picis 1 volt and pressurepicis zero psig and 20mA when picis 5 volt and pressurepicis at maximum range picof the bellows. Hence the transmitter voltage outputpic in volt and current outputpicin mA may be written as, pic (13) and pic (14) From (13) and (14), pic (15) where picand pic(16) pic Fig. 2. Block diagram of the proposed pressure transmitter using bellows element as sensing device pic Fig. 3 Circuit dia gram of hall probe based pressure indicator IV. EXPERIMENT The experiment is performed in two steps. In the first step, the proposed transducer was designed, fabricated and mounted on the outside cover of bellows chamber as shown in Fig. 1. The bellows with the above sensor was first fitted with a at peace(predicate) weight tester and the dead weight of the dead weight tester was increased in steps and in each step the Hall voltage output is measured and the characteristics of the hall sensor based transducer unit is determined.The characteristic graph obtained by plotting Hall voltage against Pressure is shown in Fig. 4. Experiment was repeated both in increasing and decreasing modes for some(prenominal) times and the standard deviation burn for six observations is shown in Fig. 6. In the second step the output of the pressure transmitter is taken in terms of current signal and he characteristic is shown in Fig. 7. pic Fig. 4 Characteristic graph obtained by plotting Hall voltag e against Pressure pic Fig. 5 Percentage deviation Curve of the Hall Probe based Pressure Transducer picFig. 6 Standard Deviation Curve of the Hall Probe based Pressure Transducer pic Fig. 7 Characteristic graph of hall probe based pressure transmitter V. DISCUSSION The characteristic of hall probe sensor is nonlinear in nature. But change of hall probe voltage is quite linear as shown in Fig. 4. The linear nature of the curve is due to the fact that the movement of the tip of the bellows for the entire pressure range is generally very small and hall probe voltage due to small change of distance between hall probe and magnet lies almost in the linear zone.The percent deviation curves from linearity as shown in Fig 5 also indicate that the percentage deviation from linearity also lies within the tolerable limit. A very good repeatability of the experimental data was also observed as shown by the standard deviation curves in Figs. 6. The characteristic of the whole transmitter is alm ost linear as shown in Fig 7. The design of the system is very simple and the hall probe & the permanent magnet are instantaneously available at a very low court. Hence the cost of the pressure transmitter will be low. References 1 J. P. Bentley, Principles of measuring rod Systems, 3rd ed. Longman capital of Singapore Publishers (pvt) Ltd. , Singapore, 1995. 2 E. O. Doeblin, Measurement System Application and Design, 4th ed. , McGraw-Hill, radical York, 1990. 3 B. G. Liptak, Process Measurement and Analysis, 3rd ed. , U. K. Butterworth Heinman, Oxford, 1999. 4 D. M. Considine, Process Instruments and Control Hand Book, 2nd ed. , McGraw-Hill, New York, 1974. 5 Raveendran, B. Subhash, K. M. Design of modular pressure transmitter with wireless capability IEEE Conference on Electrical, Electronics and Computer Science (SCEECS), 2012, pp 1 3 6 Bera, S. C. Mandal, N. Sarkar, R. Study of a Pressure Transmitter Using an Improved Inductance Bridge Network and Bourdon Tube as Transdu cer IEEE Transactions on Instrumentation and Measurement, Vol 60 , national 4 , Year 2011 , pp 1453 1460 7 Yaocan Ruan Minghao He Shuran Song Tiansheng Hong Multipoint wireless pressure spy system 2nd International Conference on Artificial Intelligence, wariness Science and Electronic Commerce (AIMSEC), 2011 IEEE Conference, 2011 , PP 4091 4094 8 Zeng Mingru You Wentang Qian Xin , The development of intelligent pressure transmitter based on HART Protocol IEEE Conference on E-Health Networking, digital Eco systems and Technologies (EDT), Vol. , 2010 , pp 121 124 9 Kanakasabapathi Subramanian, Jeffrey B. Fortin, and Kuna Kishore, Scalable vertical diaphragm pressure sensors device and process design, design for packaging IEEE Sensors Journal. , vol. 6, no. 3, June 2006, pp. 618-622 10 S. Y. Yurish, Intelligent digital pressure sensors and transducers based on universal frequency-to-digital converters (UFDC-1), Sensors & Transducers Journal. , vol. 60, no. 10, October 2005, pp. 4 32-438. 11 Radimir Vrba, Miroslav Sveda and Karel Marecek, Pressure transducer with multiplexed frequency transmitter, Slconi04 Seoron for industry Conference, New Orleans, Louisiaiib, USA, 27th -29th January, 2004, pp. 07-10.