Design and Implementation of a Temperature Measurement System Using RTD - Coursework Example

DESIGN AND IMPLEMENTATION OF A TEMPERATURE MEASUREMENT SYSTEM USING RTD Name Institution Instructor Date Contents Introduction 3 Objectives 4 Experimental Apparatus 4 Experimental procedure 5 Procedure: Stage 1 5 Voltage reference 6 Inverting amplifier 7 Calibration 8 Experimental procedure for stage 2: 8 Theory and calculations 9 Theory of Operation 9 RTD Specifications 10 Temperature Coefficient 11 Nominal Resistance 11 Wiring Configuration 11 Temperature Range 12 Accuracy 13 Presentation of results 13 Discussion and results 16 Conclusion 18 References 19 Introduction Resistance temperature detectors are made up of metals having elevated temperature coefficients that are positive. All metals experience an increase in resistance following a corresponding increase in temperature. The proportionality that relates metal resistance and the absolute temperature is the direct proportionality. The absolute temperature in this case represents a measurement of the heat average density displayed by a material with regard to the point of the absolute zero that signifies the stoppage of all molecular motions. The measurement of the absolute temperature takes place and is expressed in terms of Kelvin or degree Celsius’ Absolute has to represent the point at which the freezing of water takes place. For different ranges of temperatures ranges different range of materials are utilised. These materials include nickel platinum and copper. These materials are preferred because they do not readily corrode and they have high melting points, which is a desirable property (Bewoor and Kulkarni, 2009). The resistance for the nickel material has a linear relationship with that of its temperature. If there is an exact proportionality, the temperature coefficient in relation to the resistance for a particular sensor that is made using resistance that is equal to 100 Ω at a temperature of 00C 273.15 Kelvin would translate to 0.3661 Ω/°. This value would only be considered to apply for a particular sensor that is in construction with a wire strip from an ideal shape of metal to give a resistance that is equivalent to 100Ω at 0°C. A generalisation of this property as opposed to that of the sensor, the resistance value is divided by the temperature value at a specified point. The nominal range of the TCR values that are available for the RTDs that are made of platinum are close to this particular ideal value. The manufacture and construction of classical resistance temperature detector (RTD) makes use of platinum. A resistance temperature detector (RTD) is a device that is use in sensing temperature. An increase in its resistance is directly proportional to that of its temperature. The (RTD) is made up of a deposited film or a wire coil from pure metal. An RTD can also comprise of different types such as metals. The metals in this case are those with varying resistances with the one having the most popular resistance temperatures detector (Ball and Ball, 2004). Objectives The objectives of this particular experiment included the following The building and calibration of a system that is used in the measuring of temperature based on Resistance Temperature Detectors Determination of the signal conditioning of the transducer and the values of its components Designing of a digital system that is used in the measurement of temperature on the basis of Resistance Temperature DetectorRTD, the conditioning of signals, acquisition of data and LAbVIEW. Experimental Apparatus RTD Power supply Water boiler computer MultiMate Variable resistance Resistors Zener diode Cables charge amplifier 16 bit processor Experimental procedure Procedure: Stage 1 The determination of the constant current passing through the Resistance Temperature Detector was done by use of the reference voltage VZ and resistors J,S and K.J. The K resistor was made to in control of the direct current offset voltage. The voltage identified as V1 from this particular stage was found to be negative and therefore the addition of an inverting voltage amplifier was made to chive to be in control of the gain and achieve a positive output. The circuit used fir the procedure in this stage I as illustrated below: Figure 1: The architecture of the temperature measurement system Figure 2: The design of signal conditioning unit Figure 3: Block diagram for the system of digital measurement of temperature Voltage reference A zener diode with a rating specification of 7.5 V was used in the regulation and delivery of voltage and current to the Resistance Temperature Detector, RTD and the current was determined to be 20 mA. The RTD constant was put at 10 mA and there the resistance determined through: The value of W was the calculated and suitable values selected and this was illustrated as indicated n the circuit diagram below Figure 4 Inverting amplifier The gain for the amplifier –M/L was obtained through calculation using the equation (6) above. The gain for the inverting amplifier was then found and used in obtaining the output voltage that correspond to a temperature of 100oC . The gain was then accorded the suitable values of L and according to the selection made. The implementation of the system and testing The experimental components were connected on the experimental board. The decade resistance box was the used in the first testing that took place as opposed to the use of the RTD. This was done to ensure the proper functionality of the circuit used. The power supply was then switched on and the voltage reference was checked using a voltmeter and it operation was confirmed to satisfactory. After this was done, V1 was then checked to ensure that its rate of increase was taking place a negative sequence from the value of 0 to that which is approximate to that obtained from equation (6). The value obtained from equation (6) was considered the substitute of RTD, which was set to vary from 100 ohms to about 140 ohms. The above experimental measurement exercise was only brief without much details and steps. All the significant errors were corrected in the course of the performance of the experiment. Calibration In this case, the decade resistance box was replaced with the RTD and the value of the output voltage measured while the temperature of water was being increased from that of room temperature to 100oC. Experimental procedure for stage 2: A data acquisition card was utilised in reading the outputs as obtained from the system of measurement. A suitable and desire GUI was designed and build using LabVIEW. As for the area that is shared, VI was used in reading voltage and the scaling of property was done in a manner that also ensured the scaling of temperature measurement. Theory and calculations Theory of Operation A primary physical feature or characteristic of a metal is that its resistivity that is associated with its electrical conductivity nature changes with the change in temperature. Most of the RTDs work on the basis of the particular principle. The most significant part of the RTD is the element of resistance. Various types of semi-supported wire-installed completely supported wound glass, as well as thin film element types are described in this case. Some metals pose a feature that causes them to display a very predictable change in resistance for a corresponding change in temperature; these are the most common materials and metals that are selected in the design and manufacture of a RTD (Ibrahim, 2002). Precision resistor is designed and fabricated from any one of these metals to a nominal value of ohm in accordance with the temperature specifications. Through resistance measurement of temperature at some values of temperature and subjecting this value to comparison with the nominal value for the resistor, it is possible to determine the changes in resistance. Since the resistance verses temperature characteristics are also are determinable, the changes that take place in temperature with regard to an initial specified point can be determined. Currently a practical sensor is used in sensing temperature. This practical temperature sensor is commonly used as a resistance element (Brock and Richardson, 2001). The features of various metals and their alloys have been subjected to experimental studies in a case that has resulted in their resistance verses temperature relationship demonstrations. For various kinds of RTD's, there exist formulas and equations that are able to result into temperature that arise from a particular resistance. This information is very significant since it plays an important role in assisting the manufacturers to offer standardized readout and devices for control that are in compatibility with most of the d types of RTD's that are widely acceptable. RTD Specifications The specification of RTD must be able address certain specific parameters when it comes to appropriate applications of these measuring systems in order to realise a desired performance specifications. Most of these parameter are those that are specified by those in charge of manufacturing at the time of manifesting. For the cases involving special OEM application or custom circuit, the designers are charged with responsibility for making all the necessary design specifications. Round four design specifications are suggested with the consideration of circuitry or the instrumentation (Bewoor and Kulkarni, 2009) . These include nominal resistance, the sensor material, the wiring configuration as well as the temperature coefficient. Various materials are commonly used for the design and manufacture of RTDs and the metal purity as well as the constriction of the element affects its features. The platinum material is regarded as a very popular material that is used in the manufacture of the RTDs. This is because it is improved linearity with regard to temperature, a wide range or operating temperature as well as excellent long-term stability. Other materials include copper, nickel, iron-nickel alloy as well as tungsten. Most of these materials are currently being replaced with sensors that are made of platinum. These materials are becoming more competitive with regard their cost and wide usage. This is the case because of an increasing demand for the resistance elements with thin film and which require a small amount of material in comparison to an element that is wire wound (Meijer, 2008). Temperature Coefficient The coefficient of temperature or the RTD alpha is an electrical and physical property the manufacturing material and the technique through which the fabrication of the element is taking place. The coefficient of temperature offers a description for the change of average resistance per unit temperature from the freezing pint up to the water boiling point. Several organization have adopted several coefficients of temperatures as their standards. Nominal Resistance The nominal resistance represents a resistance that is initially specified at a specific value of temperature. Most standardized parameters include those that are used as reference points due to their ease o production. The specification in accordance with the International electro technical Commission are based on 0°C at 100.00 Ohms. However, the nominal resistances are widely available and common. The thin film technology is associated with several advantages and benefits, which include elemental that are small. This property makes them to be economical in the end (Meijer, 2008). Wiring Configuration The wiring configuration is a representation of the parameter that is typically specified with the one in charge of manufacturing. However, the designer of the system has little control with regard to the application of the system. An RTD is a device that is inherently made up of 2-wires. However, resistance from the lead wire can result into drastic reduction of the measurement accuracy through the enforcement of an additional resistance that is uncompensated in the system. Several applications require a third wire to play a role in assisting the manufacturer in providing a true indication for the measured value of temperature. RTDs that are using four wires offer better and more reliable compensations. However, they are generally available only in laboratory equipment as well as in other cases where high accuracy is required. When the wiring configuration is used together with a three-wire instrument, a four wire RTD does not offer a better accuracy. If there is no connection of the fourth wire, there are chances of introducing new errors. The connection of a three wire RTD to a four-wire instrument may bring about significant errors. However, this depends on circuitry of the instrument. A two wire RTD can be utilised in combination with a three or a four-wire instrument through skipping a terminal, although this brings about difficulties with regard to the objectives. To obtain an optimum performance, it is usually important to specify the RTD according to the recommendations from the manufacturer (Ibrahim, 2002). Temperature Range With regard to the ASTM, RTD's that are made of platinum can obtain temperature measurements from -100°C to 750°C. It is important to consider, the limitation of temperature for all the materials that are involved, their places of application as well as the temperatures to which they are exposed. This can be illustrated through the case of a few examples such as: TFE Teflon is supposed to be used for the insulation of wire upon its exposure to temperatures that are more than 200°C or 250°C for others. The proof of moisture seals are commonly manufactured using a variety of epoxy that has general limitations below the insulation for Teflon. Several materials that are used in wire insulation attain a brittle feature at temperature measurements of sub-zero For that reason several wire insulation materials are not supposed to be used for cryogenic work. Handle the state that is identified with the intended range of temperature should with the assistance of a designer. Accuracy Since RTDs are generally portrayed and understood with regard to their enhanced degrees of accuracy and is, a typical of the initial laid out specification. When it comes to the accuracy that that is associated with RTDs, it is important to establish the difference that exist between precision, accuracy and repeatability. When it comes to the accuracy that is associated with temperature, there is a common definition with regard the manner in which the Presentation of results results of data to used to produce the equation of the system Temperature () 0 25 50 75 100 Resistance () 100 110 120 130 140 Voltage (Volts) -0.1 2.51 5.87 7.80 9.88 Results of data gathered from the finished system. RTD raw temperature data () 17 20 21 22 24 26 28 29 32 33 35 37 39 41 42 45 47 48 50 53 54 56 58 60 62 64 66 68 70 72 73 75 77 79 80 Corresponding digital thermometer temperature readings () 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 LabVIEW and Data acquisition The objective of the these exercise include The gaining relevant and useful experience with regard to the use of LabVIEW towards to the accomplishment of typical tasks of data acquisition To obtain familiarisation when it comes to the data acquisition instruments and the LAbVIEW software To come up with a simple system of measurement that is capable of making use of computer aided instruments upon which subsequent design work can be built The LAbVIEW exercise comprises two parts. The first part is the panel in front together with a control set that is utilised by the use in performing manipulations while the system is still in use. The second part is the one that contains the block diagram as well as a group of actions that are collectively brought together. The panel in front can be subjected to customization for any desirable appearance, whereas the block diagram can be subjected to manipulation to indicate a clear data flow from its source to a desired destination. When the labVIEW system is in operation, there is the back and forth movement is experienced through the entire system. Discussion and results Several of the applications that are currently applied mechatronic related applications include the measurement of some parameters, displaying and the processing of data is important. The purpose for this component of the experiment is important in the use of mechatronic application. It aimed at the development of the knowledge and skills that are useful and important in the application of the theoretical knowledge gained during theoretical studies. This part was found to be very significant since it involved the LabVIEW creation with regard to virtual instrument. This enabled the reading and analysis of data that was found to have been displayed on the screen following the performance of the experiment (Ibrahim, 2002). Signal conditioner The calculations for use in signal conditioner employed the use of several equations. These equations played a significant role in designing the signal conditioning circuit with rating and specifications as follows: Vz = 7.5, I= 10mA and the value of were then found using the equation as indicated below. The value of X that was calculate in this case represented the factor for potential divider for parameters J and K as well as S. The nearest value of S that is preferred was then selected after which the K and J values were calculated to obtain the desired value of x. The current limiting values that were prefer were ten selected and which has the value of 1 mA. The following equations were then utilised in the calculations of the maximum value of the output voltage. The use of virtual instrumentation enabled the acquisition of voltages from the power supply before their measurement was done and translated from the computer interphase to the physical quantities. The requirement of size and physical dimensions were found to be more complex. This is because there has to be a use of resistance on the lower end. This resistance used is important since is it plays a major role in in the design and manufacture of a sheathed RTD which requires a generally small elements that are capable of fitting the required shape and size of the sheath used. For the elements that are cylindrical in nature such as the wire wound elements that are smaller in comparison to the others (Puttlitz and Totta, 2001). The thin types of elements were found to be appropriate with regard to application in RTD assemblies and probes. The discussion with regard to the RTD probes ad assemblies includes a careful examination of the arrangement that was used in the mounting exercise. This is because it is needed in deciding whether to use an immersion with a thermo-well or the use of a direct immersion. The designs for RTD probes contain endless features that form part of their configurations. In most applications, the immersing of the probe is used through a small piping system or small vessel (Brock and Richardson, 2001). Conclusion In conclusion, the design and implementation of a temperature measurement system that uses RTD proved to be significant with regard to meeting the requirements of the and objectives of the experimental performance. The design and use of the calibration system for use in the measurement based on Resistance Temperature Detector was an important step in equipping the participants with the necessary skills and knowledge. The performance of this particular experimental design was also found to be critical in the determination the signal conditioning of the transducers and this played an important role in obtaining the values that are related with the components as they were used and applied. This particular design experimentation performance provided a detailed explanation of the components form part of the RTD temperature measurement system. In addition, the experiment was significant in understanding the theory that is associated with the design and operating principles of the RTD system of measuring temperature. References Ball, S. R., & Ball, S. R. (2004). Analog interfacing to embedded microprocessor systems. Amsterdam, Newnes. Bewoor, A. K., & Kulkarni, V. A. (2009). Metrology & measurement. New Delhi, Tata McGraw-Hill. Brock, F. V., & Richardson, S. J. (2001). Meteorological measurement systems. Oxford, Oxford Univ. Press. Collett, T. S., Johnson, A. H., Knapp, C. C., & Boswell, R. M. (2009). Natural gas hydrates: energy resource potential and associated geologic hazards. Tulsa, Okla, American Association of Petroleum Geologists. Ibrahim, D. (2002). Microcontroller-based temperature monitoring and control. Oxford, Newnes. Meijer, G. C. M. (2008). Smart sensor systems. Chichester, U.K., J. Wiley & Sons. Puttlitz, K. J., & Totta, P. A. (2001). Area array interconnection handbook. Boston [u.a.], Kluwer Academic Publ. Read More

This practical temperature sensor is commonly used as a resistance element (Brock and Richardson, 2001). The features of various metals and their alloys have been subjected to experimental studies in a case that has resulted in their resistance verses temperature relationship demonstrations. For various kinds of RTD's, there exist formulas and equations that are able to result into temperature that arise from a particular resistance. This information is very significant since it plays an important role in assisting the manufacturers to offer standardized readout and devices for control that are in compatibility with most of the d types of RTD's that are widely acceptable.

RTD Specifications The specification of RTD must be able address certain specific parameters when it comes to appropriate applications of these measuring systems in order to realise a desired performance specifications. Most of these parameter are those that are specified by those in charge of manufacturing at the time of manifesting. For the cases involving special OEM application or custom circuit, the designers are charged with responsibility for making all the necessary design specifications.

Round four design specifications are suggested with the consideration of circuitry or the instrumentation (Bewoor and Kulkarni, 2009) . These include nominal resistance, the sensor material, the wiring configuration as well as the temperature coefficient. Various materials are commonly used for the design and manufacture of RTDs and the metal purity as well as the constriction of the element affects its features. The platinum material is regarded as a very popular material that is used in the manufacture of the RTDs.

This is because it is improved linearity with regard to temperature, a wide range or operating temperature as well as excellent long-term stability. Other materials include copper, nickel, iron-nickel alloy as well as tungsten. Most of these materials are currently being replaced with sensors that are made of platinum. These materials are becoming more competitive with regard their cost and wide usage. This is the case because of an increasing demand for the resistance elements with thin film and which require a small amount of material in comparison to an element that is wire wound (Meijer, 2008).

Temperature Coefficient The coefficient of temperature or the RTD alpha is an electrical and physical property the manufacturing material and the technique through which the fabrication of the element is taking place. The coefficient of temperature offers a description for the change of average resistance per unit temperature from the freezing pint up to the water boiling point. Several organization have adopted several coefficients of temperatures as their standards. Nominal Resistance The nominal resistance represents a resistance that is initially specified at a specific value of temperature.

Most standardized parameters include those that are used as reference points due to their ease o production. The specification in accordance with the International electro technical Commission are based on 0°C at 100.00 Ohms. However, the nominal resistances are widely available and common. The thin film technology is associated with several advantages and benefits, which include elemental that are small. This property makes them to be economical in the end (Meijer, 2008). Wiring Configuration The wiring configuration is a representation of the parameter that is typically specified with the one in charge of manufacturing.

However, the designer of the system has little control with regard to the application of the system. An RTD is a device that is inherently made up of 2-wires. However, resistance from the lead wire can result into drastic reduction of the measurement accuracy through the enforcement of an additional resistance that is uncompensated in the system. Several applications require a third wire to play a role in assisting the manufacturer in providing a true indication for the measured value of temperature.

Read More