• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Investigating a Thermistor.

Extracts from this document...

Introduction

INVESTIGATING A THERMISTOR After deciding to investigate the properties of a thermistor, I chose to be more specific, and to look at repeatability, accuracy, and sensitivity. I also thought of many different ideas as to what the experiment could be used for: for fridge...??? controlled???. The proceeded by looking at different circuits suitable for exploring sensitivity. I looked into the 'whetstone bridge' circuit: The wheatstone bridge circuit enables more accurate readings, However, I decided on another circuit that acted as a potential divider only using one fixed resistor, which seemed equally suitable for detecting small changes of volts. The reason for this being that I thought it would be interesting to see the effect(s) of changing the fixed resistor (R): After recognizing the importance of (R), I decided on the equipment I was going to use, and then tried using some algebra to tackle the problem of finding the value of R that would give me the biggest change DVo. Equipment: 1 power generator set at 2volts 1 thermistor (RS 0.47Kohms 232-4538) an assortment of fixed resistors some leads some crocodile clips a digital voltmeter Here are my jottings: Vo/Vs=R/R+RTh Vo=Vs(R/R+RTh) (Vo=Vo t2 - Vo t1 (Vo=VsR[1/ R+RTh t2 - 1/ R+RTh t1] At this point I thought it appropriate to take a numerical approach, and use Excel to plot a graph of the equation as I was having difficulty simplifying or manipulating it further. ...read more.

Middle

Bellow are a few diagrams to illustrate this: Experiment: After gaining my background knowledge, and after doing my planning, I felt I was ready to start my experiments. I decided to produce more accurate results, that I would take two sets of results, which would also help to test for repeatability. I started by testing the 470ohm resistor, and the results are as follows: Vo(volts) set 1 Vo(volts) set 2 Average Vo Temp. (degrees Celsius) 1.86 1.86 1.86 86 1.85 1.85 1.85 85 1.83 1.85 1.84 84 1.84 1.84 1.84 83 1.83 1.85 1.84 82 1.83 1.83 1.83 81 1.82 1.82 1.82 80 1.82 1.82 1.82 79 1.8 1.82 1.81 78 1.8 1.8 1.8 77 1.8 1.8 1.8 76 1.79 1.79 1.79 75 1.79 1.74(void) 1.79 74 1.77 1.79 1.78 73 1.77 1.77 1.77 72 1.77 1.77 1.77 71 1.75 1.77 1.76 70 1.75 1.75 1.75 69 1.73 1.75 1.74 68 1.74 1.74 1.74 67 1.73 1.73 1.73 66 1.71 1.73 1.72 65 1.7 1.72 1.71 64 1.71 1.71 1.71 63 1.7 1.7 1.7 62 1.7 1.68 1.69 61 1.68 1.68 1.68 60 1 1.66 1.66 59 1.65 1.65 1.65 58 1.65 1.63 1.64 57 1.63 1.63 1.63 56 1.62 1.62 1.62 55 1.59 1.61 1.6 54 1.59 1.59 1.59 53 1.58 1.58 1.58 52 1.57 1.57 1.57 51 1.56 1.56 1.56 50 1.54 1.54 1.54 49 1.53 1.53 1.53 48 1.51 1.51 1.51 47 1.5 1.5 1.5 46 1.5 1.48 1.49 45 1.47 1.47 1.47 44 1.46 1.46 1.46 43 1.45 1.45 ...read more.

Conclusion

To try and justify my results, I went back to my equation (Vo=VsR[1/ R+RTh t2 - 1/ R+RTh t1] However I manipulated it to give me the specific value of RTh, not a range of values: (Vo=VsR[1/ R+RTh] I proceeded to plot these graphs on Excel: I was then faced with the problem of converting 'resistance of Rth' into temperature, and at first thought that the best way to do this was to was by finding the equation of the line of the calibration graph provided by RS. However, I faced with the problem of logarithmic scales, and due to the large jump in numbers, thought that the equation I produced would not be accurate enough. However, from the 5 ohm graph is clear that DVo increases rapidly with low values of resistance, which still contradicts the calibration graph. The graph of the 100ohm resistor is harder to tell which for which values gives a sharp increase in DVo, as the curve is quite steady. Therefore I am none the wiser as to why my results given do not indictate that 100ohms is more sensitive to low temperatures, and 5ohms is more sensitive to high temperatures. Unfortunately I ran out of time with this project, however I would have liked to have taken more readings, and a second set of results for the experiments above. However, I do think that they were sufficient to conclude that the thermistor has good repeatability, and also that there was little difference between using the 560ohm and 27k ohm fixed resistors. Also, from the fixed resistors I evaluated, 100ohms appears to be the most sensitive. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Electrical & Thermal Physics essays

  1. Marked by a teacher

    Sensing project

    5 star(s)

    The same fixed resistor is used thought out the experiments so as to ensure the variables remain constant. The resistor that will be used in the circuit will be a 10K? resistor, which has similar resistance to the rotary potentiometer.

  2. Investigate how the temperature affects the resistance of a thermistor.

    to 1000C; anything that has a smaller scale is not necessary because I am only measuring whole temperatures (not decimals) but anything that has a larger scale may not be as easy to read and so could not give results that are as precise.

  1. I am going to investigate what the resistivity is of a pencil lead. ...

    The electrons also have more energy so move faster meaning that there are more collisions between positive ions and electrons hence an increase in the resistivity. Errors The result that I have got for the resistance and the resistivity may not be accurate because of the limitations of the tools

  2. Sensors Project Report

    Resolution From the experiment and results that is given we can detect the numbers of sheets of paper from 1 sheet to 100 sheets. The small change which can be detected is 1 sheet from the graph we can see.

  1. AC Generator

    fast, it could cause a short circuit or destroy the whole project. Keep the hand drill on a safe speed . Testing and Modifications: * The way I placed the magnets failed to get the generator producing current so I had to get more magnets and place them around the whole armature.

  2. silicon project

    into large quantities often develop a serious lung disease known as silicosis. Explain table Atomic Radius: A measure of the size of an atom, assuming the atom has the shape of a sphere. Slide 6 Silicon is a very useful element that is vital to many human industries.

  1. For my sensor project coursework I will be investigating a thermistor.

    a component can be 'tapped off', thus giving a divided proportion of the total potential difference. The circuit used is shown below. Another way this circuit can be used is to sense a change in the surrounding environment. This can mean substituting one of the fixed resistors for a form of variable resistor.

  2. Test how a thermistor reacts to temperature. Also how the results compare to the ...

    N-type silicon is a good conductor. Electrons have a negative charge, hence the name N-type. P-type - In P-type doping, boron or gallium is the dopant. Boron and gallium each have only three outer electrons. When mixed into the silicon lattice, they form "holes" in the lattice where a silicon electron has nothing to bond to.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work