Oscilloscope
Laboratory Experiment
Using
Temperature Sensor(s)
Here we give you an opportunity to begin learning how to use an oscillscope.
If you need to review what an oscillscope is and what it does, click
here. In that lesson link you can experiment with a simulated
oscilloscope to get an idea of what to expect with a real oscillscope.
You need to remember these important points about an oscilloscope:
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An oscilloscope is a voltage
measurement device.
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Unlike a voltmeter, an
oscilloscope does not display a single number.
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An oscilloscope displays
signals - voltages that are functions of time.
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So, an oscilloscope measures
voltages that change with time and gives you a graph of how they vary with
time.
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Oscilloscopes can measure
signal
parameters - like frequency, peak-to-peak
voltages, RMS values of signals, etc.
Since an oscilloscope displays time-varying signal, you need a voltage
source that produces a time-varying signal. For this introductory
exercise, we will just use a temperature sensor, and you will change the
temperature by grabbing hold of the temperature sensor, causing it to change
from room temperature to your body temperature. You need to connect
the LM35 temperature sensor to the oscilloscope as shown below. The
LM 35 circuit is the one you used earlier.
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Now, set the oscilloscope
to the longest time setting. With most oscillscopes you should be
able to get a trace that takes many seconds to cross the width of the screen.
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Normally, an oscilloscope
will have settings like 1 msec/div, 2msec/div and 5 msec/div. You
actually want something like 1sec/div, or 2sec/div - as high as you can
get.
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You also want to set the
oscilloscope so that you can see the voltage when it changes. You
should be getting a fraction of a volt
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As the trace starts across
the screen, grab hold of the LM35. You should get a plot of the temperature
(actually, for the LM 35, a plot of a voltage proportional to temperature
in Celsius).
When you are finished return to the main laboratory page.