ENGT 5214 Research Methods - Free Samples to Students

ble to be used in the alexandrite laser pole. The objective of this task is to find a method (method B) to keep up the alexandrite laser pole at some predetermined temperature in the range of 25?C and 99?C, with a precision ranging from positive to negative 3 degrees.

The most commercially available and the most suitable negative coefficient of temperature thermistors are used for the purpose of temperature controlling. It has a little impression permitting advantageous implanting into different equipments and is exceedingly receptive to little temperature changes.

Compared with the positive coefficient of temperature thermistors the negative coefficient of temperature thermistors efficiently perform under various range of temperatures between 40 to 140 ⁰C which is the required and recommended range of temperature for the alexandrite laser. These artistic semi-conductors show a decrease in electricity as the temperature rises, they also have a steady and repeatable voltage and temperature trademark bench.

The name thermistor gets from the words "heat" and "resistor". Thermistors are temperature delicate aloof semiconductors which display a substantial change in electrical opposition when subjected to a little change in body temperature. Thermistors are fabricated in different sizes and shapes. Globules, circles, washers, wafers, and chips are the most generally utilized thermistor sensor writes. Plate thermistors are made by mixing and compacting different metal oxide powders with appropriate fasteners. The plates are shaped by packing under high weight on pelleting machines to create round, level clay bodies. At long last, the thermistors are subjected to an extraordinary maturing procedure to guarantee high steadiness of their qualities.

Temperature and measurement literature review

Temperature measurement is defined as the measurement of velocity of fluid particles. Temperature is a property of a body which is generally used in order to find the degree of hotness or coldness or the heat intensity level of an object. The second law of thermodynamics is relates the temperature to heat. The second law of Thermodynamics is also known as the law of entropy which states that the entropy of a system keep on increases and it never decreases. The clausius law stated that there is no heat engine which transfers heat from a cold body to hot body, which means the heat cannot flow from a cold body to hot body it can only flow from a hot body to cold body. Thus the heat flow can only be from a higher temperature element to a lower temperature element.

In today’s world the temperature measurement is a very vital thing to run our day today life the temperature measuring instruments are all around the society in the Air conditioners, HVAC systems, Cars, two wheelers, etc. There are wide variety of temperature measuring instruments that available these days some of the most important and widely adopted instruments are the thermometers, pyrometers, bimetallic strips, pressure thermometer, thermocouples, Electrical resistance thermometers, filled system temperature measurements, etc.

The thermometers are the instrument that are used to measure the temperatures in ordinary range in other word lower temperature ranges, the thermometer generally uses a liquid metal such as mercury which will expand when exposed to a temperature that expansion will be within the given area for the mercury to rise that area is a tubular section marked with gradual readings of temperature, thus a temperature of a body is found. The mercury thermometers are not the only thermometers there are wide variety of thermometers available in the market commercially today they are the thermometers are not suitable for higher temperature measurements.

The instruments used to measure high temperature range is known as pyrometers. The pyrometers measures the temperature based on the change in intensity of the radiation and the radiation colour. The temperature measurement method by radiation is the basic principle of pyrometers. If we can find the thermal radiation emitted by the body we can be able to find the temperature of the body. There are three types of pyrometers used widely and available commercially they are Total radiation pyrometers, which measures the body temperature with the help of a concave mirror focused to the thermocouple the second type of pyrometer is the Infra-red pyrometer, which work on the basis that at high temperatures the body starts to emit infrared rays also some visible rays which are visible to naked eye, with the help of a detector and some electronic circuits the intensity of the Infrared rays are measured which is proportional to the temperature of the particle. The infrared pyrometers can be used to measure the temperature of particles up to a maximum range of 400 degree Celsius. The third and the last type of pyrometer is known as the Optical radiation pyrometer, which uses a lamp which is connected to an ammeter at the middle, lens at one end and eye piece at the other end. The body to which the temperature to be measured is placed behind the optical pyrometer instrument, then the filament (lamp) is adjusted to match the brightness of the heat source, which is the object whose temperature to be measured, the outcome would be equal brightness with the brightness level of the heat source or the lamp will be darker than the heat source or the lamp might be in a more brighter stage than the heat source. The requirement is to bring the filament brightness equal to the brightness of the heat source then the current input to the filament is measured using the ammeter thus the temperature corresponding to the current flow can be measured with the help of optical pyrometers.

The pressure, electrical resistance, expansion coefficient, etc are all interrelated with the temperature in its basic molecular structure itself so these variables can also be used in the measurement of temperature. We have seen the usage of pressure and expansion application for the temperature measurement in case of thermometers and electrical resistance in case of pyrometers, thermocouples, etc.

Temperature is a standout amongst the peak imperative bounds in control process. The measurement of the exact temperature isn't simple and in order to get correctness superior to anything 0.5°C incredible care is required. Mistakes happen because of a few sources, for example, temperature angles, faulty sensors, alignment blunders, and poor heat conduction. There are numerous kinds of equipment to measure the temperature called temperature sensors. A few sensors, for example, the thermocouples, Negative temperature coefficient thermistors, positive temperature coefficient thermistors, Resistance temperature detector and the thermopiles are the more established traditional sensors and they are utilized mainly because of their big favourable conditions. The latest sensors, for example, the incorporated circuit sensors, the radiation thermometry equipments are established just for constrained applications. Resistance temperature detectors are utilized as a part of medium temperature range, going from -190 to +595°C. They offer high exactness, commonly with deviation of 0.2°C. Resistance temperature detectors can more often than not be utilized as a part of most compound and physical conditions; however they are not as strong as thermocouples. The activity of Resistance temperature detectors requires outside power supply. The choice of proper sensor isn't generally simple and it relies upon variables, for example, the precision, the temperature run, speed of reaction, heat coupling, nature, and the cost. Ecological applications, hardware pastime advertise, and car enterprises for the most part utilize thermistors or coordinated circuit sensors.

Thermistor temperature sensor

Thermocouples are straightforward temperature sensors comprising of two different metals combined. In 1821, the generation of thermoelectric voltage was found and an electric current was discovered streaming in a shut circuit of two unique metals, if the two intersections were held at various temperatures. One of the intersections was assigned the hot intersection and the other intersection was assigned as the chilly or reference intersection. The current created in the close circle was relative to the kinds of metals utilized and the distinction in temperature between the hot and the icy intersections. Thermocouple wires are generally made of various metals from the measuring equipment wires and subsequently, an extra match of thermocouples is shaped at the association focuses. In spite of the fact that, these extra thermocouples appear to cause an issue, the utilization of the Law of Intermediate Metals demonstrate that these thermocouples have no impact, on the off chance that they are kept at a similar temperature. There are around 12 standard thermocouple composes that are generally utilized. Each compose is given a universally affirmed letter that shows the materials from which the thermocouple is fabricated.

There were two experiments which were conducted in order to accomplish the final goal of the task: the first step is to align the thermistor alongside above equations, the second is to test the first setup as a temperature controller. The program is executed in a national Instrumental Lab computer microchip, which is powered by a program executed with an Intel Core 2 Duo 2.93 Ghz processor with 2 GB of DDR2 ram running an operating system of windows 7. The adjusting equipment which is used to adjust or to calibrate is a mercury thermometer.

Each of the radiator and thermistor are stuck against a small opening in a little metal box in order to enhance the precision of temperature measurement which is carried out at the surroundings of the heating element. The electric potential across the thermistor, denoted by VT, is calculated at by the Lab computer microchip consists the port ADC2. When the temperature varies, the adjustment at VT will be estimated.

The thermistor temperature changes are noted along the process of heating as well as cooling. The value of the RT are calculated and noted for temperature ranging from 30 degree Celsius to 89 degree Celsius and at 3 degree Celsius augmentations for the heating process and down up to 29 degree Celsius for amid cooling. The temperature moderator circuit diagram is shown below.

The model is worked by writing the objective temperature, TSET, into the computer charge provoke, to initiate temperature measurement. In chances that the present temperature is lower than that of the objective temperature. At the port P_A0 of the chip would yield 5 Volts, by which the radiator is turned ONN. The flag is kept up till at the point that the temperature surpasses TSET by a counterbalance of temperature change. Then the voltage of the port P_A0 would be set to zero, which in turn will turn off the radiator. In this way, when temperature goes low under the TSET due to the temperature change, the radiator is betrayed. In the current usage, temperature change equal to 1?C serves to diminish the recurrence of killing the radiator on and, to broaden its life expectancy, while as yet controlling the temperature sufficiently tight.

The heating and the cooling curves are plotted on a graph which having (1/T) along X axis and the (ln R) along Y axis, we can see that the plot is exhibiting a hysteresis circle which is situated near the mean relapse line, this might be due to the usage of the mercury thermometer during the experiment. The thermometer exhibits change in temperature in a slower manner while heating and rapid and speeded up manner while cooling.

Conclusion

Thus the experiment is carried out with a Negative temperature coefficient thermistors which will exhibit a character as with an increase of temperature the resistance decreases, that if it is suitable for the usage as a temperature controller for the alexandrite laser pole which should be working under a predefined range of temperature between the 29 degree Celsius to 89 degree Celsius, with an accuracy of plus or minus 3 degree Celsius. The thermistor is arranged in order to comply with the Stenhart- Hart Equation which is appropriate for thermistors. This condition is selected due to its level of adjustments. Thus the experiment is carried out using a microchip lab computer powered by an Intel core 2 duo personal computer with 2 GB of DDR2 RAM and running on a windows 7 Operating system. Then the results are obtained and the graphs are plotted. The result came as that, the selected Negative thermal coefficient thermistor is suitable for the operation of the laser pole as a temperature controller. In order to achieve accuracy in the experimental results, it is highly suggested to take more than one reading and finally taking the average among them by this method way we can achieve high precision.

A more grounded radiator ought to be utilized to check if the thermistor conduct at temperatures from 88 degree Celsius to 100 degree Celsius, in order to decide whether the selected negative thermal coefficient thermistor meets the necessities of the purpose, however there ought to be no motivation behind why it can't. Also, the test for the temperature control carried out with the objective temperature set at 50 degree Celsius. Furthermore tests ought to be kept running along the temperature ranging from 30?C to 100?C to additionally confirm its execution. The number of times that the heater being turned on and off plays an important role in case of increasing the life expectancy of the radiator, the largest measure of the counter temperature from the objective temperature, and the temperature change.

References

Park, P., Ruffieux, D., & Makinwa, K. A. (2015). A Thermistor-Based Temperature Sensor for a Real-Time Clock With $pm $2 ppm Frequency Stability. IEEE Journal of Solid-State Circuits, 50(7), 1571-1580.

Chagas, A. M., Prieto-Godino, L. L., Arrenberg, A. B., & Baden, T. (2017). The€ 100 lab: A 3D-printable open-source platform for fluorescence microscopy, optogenetics, and accurate temperature control during behaviour of zebrafish, Drosophila, and Caenorhabditis elegans. PLoS biology, 15(7), e2002702.