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Oscilloscope question

Can anyone help with 3b on how you work it out, here's the link:

http://www.tomred.org/uploads/7/7/8/3/778329/electricity_qp_june_2008.pdf


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Original post by Jimmy20002012
Can anyone help with 3b on how you work it out, here's the link:

http://www.tomred.org/uploads/7/7/8/3/778329/electricity_qp_june_2008.pdf


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r.m.s = peak / sqrt 2

ooops answered wrong bit, back in a moment.

OK. So you need to work out the voltage across R2 as a fraction of the input voltage. Use the potential divider equation for this.

The voltage across R2 will follow the input in the ratio of VR2 = VIN*potential divider ratio.

Calculate VR2 peak voltage corresponding to VIN peak and draw the trace using the scale 10V/division. The time base (x-scale) does not change.
(edited 10 years ago)
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Jimmy20002012
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Original post by uberteknik
r.m.s = peak / sqrt 2

ooops answered wrong bit, back in a moment.

OK. So you need to work out the voltage across R2 as a fraction of the input voltage. Use the potential divider equation for this.

The voltage across R2 will follow the input in the ratio of VR2 = VIN*potential divider ratio.

Calculate VR2 peak voltage corresponding to VIN peak and draw the trace using the scale 10V/division. The time base (x-scale) does not change.


Still don't get it,

IV done the potential divider equation by:

63.6 x 80/80+400= 10.8 V

Now what....


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Original post by Jimmy20002012
Still don't get it,

IV done the potential divider equation by:

63.6 x 80/80+400= 10.8 V

Now what....


Posted from TSR Mobile


You don't need to use the rms voltage calculation, simply use the pk - pk voltage of the input waveform. You should get an exact integer result for the VR2 pk-pk.

The trace on oscilloscope 2 will be a sinusoid of the same frequency as the input with different amplitude modified by that potential divider. But you plot it against a changed y-scale. i.e. 10v/division not the 30v/division of oscilloscope 1.

The examiners want to see you understand the concepts and wont worry too much about the absolute accuracy of your oscilloscope 2 trace as long as it looks like a sine wave following replication of the input sinewave with the correct positions for the nodes and anti nodes. i.e. peak levels and zero crossing points.

Think of it as almost a tracing job with reduced pk amplitude plotted on a different y-scale only.
(edited 10 years ago)
Original post by Jimmy20002012
Still don't get it,

Now what....

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How far did you get after I posted the explanation?

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