• 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)

    So there is not a stage in the experiment when the rotary potentiometer is has 0 ?. In practise this is not the case as all components will have a certain internal resistance in some situations it is a benefit to have a low internal resistance.

  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. Experiments with a thermistor

    A cardboard 'wall' can be excluded in this case. * The change in output was not largely significant, with a rise of only around 0.01-0.08 V for each reading taken, and I was only able to obtain distance values for up to 16cm.

  2. To investigate how the temperature affects the resistance of a thermistor.

    I decided on this method because if I was to just heat the thermistor over the Bunsen burner then inevitably the plastic coating around the component would melt and damage the equipment. Neither could I heat the thermistor in a water bath because if then I was just be heating

  1. AC Generator

    Thus making it harder to produce a current. * More suitable way of measuring the speeds - since the hand drill wasn't very accurate in determining the speed, I couldn't speed a constant for each speed limit for each trails thus it couldn't be accurate.

  2. silicon project

    It has also shown promise for large-area, low-cost solar cells. * Construction - Silica is a major ingredient in bricks because of its low chemical activity. Slide 7 Silicon (Latin silex, silicis meaning flint) was first identified by Antoine Lavoisier in 1787, and was later mistaken by Humphry Davy in 1800 for a compound.

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

    This also means that the difference in the voltage over the difference in the current equals the resistance - due to the formula R=V/I. 6. Once I have worked out the resistance I can then work out the resistivity of the pencil lead by putting it into the resistivity equation (above).

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

    Phosphorus and arsenic each have five outer electrons, so they're out of place when they get into the silicon lattice. The fifth electron has nothing to bond to, so it's free to move around. It takes only a very small quantity of the impurity to create enough free electrons to allow an electric current to flow through the silicon.

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