Thermometer Working Principle

1. Connect the DL100 data logger with the PC and the temperature sensor

2. a. Dowload the experiment files
   b. Run the iLab software
   c. Open the experiment file: T-D.dis using iLab

– OR –

2. d. Run the iLab software and in the main menu select  «Setup» (pic. 1). Make sure that the “DL100” option is already chosen.(pic. 2)

3. In the main menu select “Start” and the experiment screen will open automatically.

4. In the experiment screen you can see the following functional areas: 

7. Stick a piece of paper (or paper tape) on the delivery tube and attach the delivery tube into the hole of the big sized rubber bang. (see the picture)

8. You can prepare the water by heating it into the glass beaker 400 ml and adding a few drops of food coloring.
9. Set up the metal base, the retort ring with gauze and the metal clamp according to the picture.

10. Place the alcohol burner on the metal base.

11. Add (heated) water into the round bottomed flask and adjust the flask to the metal clamp. Seal the flask with the rubber cap.

12. Insert the temperature sensor probe into the delivery tube. The water level will rise and it will appear to the tube. (Add a few drops of water if necessary).
13. With a ruler and a pen mark the water level in the tube, drawing a line on the paper you stuck in step 7.
14. Then, per half a centimeter draw a line.

15. Turn on the alcohol burner and on the iLab select “Manually (F7)” to take the first measurement before the volume changes.
16. Whenever the water level increases by half a centimeter (reaches the next line you marked on the paper) press again “Manually (F7)” to take the next measurement.
    
    At the end you will have a graph like the one in the image. However the graph is not useful for your calculation because you need a level of water-temperature graph and not a time-temperature graph.

Note: You can find our measurements in the experiment file T-T.dis that you downloaded in step 2.a.

17. You know that every measure you made was when the fluid level increased by 0.5 cm. You will therefore introduce a new parameter that reflects the height of the tube in centimeters.

18. To create the Distance(cm) – Temperature (°C) graph:
    • select “Add line (F3)”
    • delete the temperature-time graph
    • add the new graph by selecting Distance at x-axis and Temperature at y-axis.

19. The graph should be similar to the image. Select “Data table (F5)”  to see details for the points of the curve. Do you believe that through these points must calibrate your thermometer?

The dependence of the volume change of the liquid in relation to temperature is linear, as we know from the mathematical expression that describes it:



ΔV volume change, V initial volume, ΔΘ temperature change and β the expansion coefficient.

Therefore, for every temperature change there is an equivalent volume change. Because of metric errors this is not completely described by the chart.

20. Select “curve management” and then make linear regression to the curve.

With a very good approximation we can assume that prices on a straight line can be expressed by the formula: y = αx + β.

The gradient of the line α describes the rate of change of temperature with respect to the liquid level in the tube.

21. Fill in the gradient α into the “curve management” and draw a proper calibration of the thermometer that you created.

Suppose that in the calibration you want:

θ = 0 °C at the point 0 of our curve. Then temperature θ = 1°C will be drawn at distance Υ from 0, where Υ: