• 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...


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.


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.


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)

    Angle of Arm (0) Estimated resistance (?) 0 0 75 25,000 150 50,000 225 75,000 300 100,000 The maximum estimated resistance for the rotary potentiometer in my experiment will be roughly 59994? as the maximum angle being measured up to is 1800 as a window would not be able to open wider than this.

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

    ohmmeter instead of a full circuit and measuring the current and voltage and then putting it into the equation. Apparatus: o Thermistor o Bunsen burner o Heatproof mat and gauze o Beaker o Test tube o Oil (regular cooking oil)

  2. 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

  1. An Investigation into the Resistance of a Thermistor, its Application as a Sensor and ...

    The most basic way of using the above information is to have a data table or calibration curve similar to that above. A thermistor just like the previously calibrated one is attached to an ohmmeter. To know the environment temperature, someone is required to read the ohmmeter's value and compare

  2. Experiments with a thermistor

    The circuit is basically made up of a 5 V power supply with a thermistor and a resistance substitution box connected in series. A digital multi-meter is connected in parallel to the thermistor, to measure the potential difference across the thermistor.

  1. Investigate the relationship between temperature and resistance in a thermistor.

    Plan Apparatus- Ammeter Thermistor Bunsen burner Tripod Clamp stand Clamp Gauze Thermometer Beaker Water Power pack Wires Crocodile clips Voltmeter I will set up the equipment as shown in the diagram. I will fill the beaker with water of room temperature.

  2. silicon project

    Other uses: * Pottery/Enamel - It is a refractory material used in high-temperature material production and its silicates are used in making enamels and pottery. * Steel - Silicon is an important constituent of some steels. * Glass - Silica from sand is a principal component of glass.

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