You should build your Low Pass filter circuit on one of the pieces of Tracked Board you have been given. To see photographic images of what your circuit should look like, just click on the image of a camera near this text.
resistor and a 0·1
F capacitor. Try to make it look as much like the photo as you can. Use different colour wires for the input, output and ground leads to make it easier to tell which is which. It is usually a good idea to adopt a favourite set of ‘usual’ colours for leads as this will help you recognise what you have built. In most cases, we would recommend using a green-covered wire for ‘earth’ or ‘0 Volts’, and colours like blue for signal input, yellow for signal output, etc. The precise colours aren’t important, though. as long as they are consistent and recognisable.
| Make a note in your labscript of the wire colours you have used for the circuit. |
). Use both inputs of your ‘scope so you can observe both the input and output voltages at the same time. In each case remember that the earth lead of each pair (i.e. the ‘outer’ of the co-axial cables) should be connected to the earth-line of the circuit, shown as the bottom line of the diagram. If you can’t see which wire of the coaxial cable is which, remember that the ‘live’ wire usually has a red coloured terminal, and the ‘ground’ wire usually has a green or black coloured one. If you are not sure, ask a demonstrator to check your leads.
and 
at a series of frequencies from about 100 Hz up to 5 kHz. Use the ‘scope to measure the frequency by observing the period of the waveform. Then plot a graph of 
against frequency.
| At what frequency does  have the value  ?
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| Draw a line on the graph at the filter’s turn over frequency |
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| Is this reasonably close to the frequency where the output/input ratio is  ?
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| Remember to label your circuit with your name and keep it to hand in with your script. |
Content and pages maintained by: Jim Lesurf (jcgl@st-and.ac.uk)