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:

• An oscilloscope is a voltage measurement device.
• Unlike a voltmeter, an oscilloscope does not display a single number.
• An oscilloscope displays signals - voltages that are functions of time.
• Oscilloscopes can measure signal parameters - like frequency, peak-to-peak voltages, RMS values of signals, etc.

• A function generator (also often referred to as a signal generator) produces standard kinds of signals for test purposes.  Those signals include sinusoidal signals, triangles, square wave signals and even random signals.
• A microphone produces signals that correspond to the sound waves that impinge on the microphone.
• A temperature transducer - like an LM35 - produces a voltage that varies in response to the temperature it experiences.  (Click here for more about the LM35 temperature sensor.)
• And there are lots more. . . .

        Here's the connections for a simple signal measurement.  The oscilloscope is being used to display the voltage output from a signal generator.  You should do that also.

• Set the frequency of the signal generator output to something like 1 or 2 kHz.
• Set the amplitude of the signal generator output to 1 or 2 volts.
• Connect the output of the signal generator to the oscilloscope.  Be sure that the two grounds are connected together.  If you use a coax cable make sure you have it connected correctly.

• Be sure that the timebase is set to something like 0.5 milliseconds/cm. A 1kHz signal has a period of one millisecond.  This setting will let you see a few cycles of a 1 kHz signal.
• Be sure that the vertical sensitivity is set to something like 0.5 volts/cm.
• Adjust the trigger.  The oscilloscope needs a signal to tell it when to start the display process - moving the dot across the screen.

• The trigger can be an external signal, the power line, or the signal you are displaying.  Usually, the dot starts across the screen when the trigger signal goes through zero volts - but you can change the voltage level if you want.  If you are using the power line, then you are triggering with a signal that usually has no relation to the signal being displayed. When that happens it is very frustrating trying to figure out why you see chaos.
• In multi-channel scopes, you can trigger off Channel 2, when you're only putting a signal into Channel 1.  If there is no signal going to Channel 2, then you have no trigger signal.  You need a trigger signal, so don't do that!  Set the scope to trigger off Channel 1 if your signal is going into Channel 1.
• It is possible to get the trigger level set incorrectly without knowing it.  If your signal never gets above 5 volts and the trigger level is at 20 volts, then you can spend a lot of time wondering why you can't see your signal.

        Being able to use an oscilloscope is an important skill for anyone who takes electrical measurements.  In this section we'll present a few things you can do with oscillscopes to get better acquainted with them.

        The first thing to do is to become acquainted with the oscilloscope you have and to learn its capabilities and limitations.  Here are some things to do.  Answer the questions on the fill-in blanks.

• While displaying a sinusoidal signal, determine the limits on time resolution for your oscilloscope.  Is the lower limit in nanoseconds/cm?  Is the highest setting in seconds/cm?  When changing the time scale note how the scale changes.  Your scope almost certainly has settings like 10, 20, 50, 100 and 200 milliseconds/cm.  Those settings almost always proceed in a 1-2-5 sequence.
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• Adjust the amplitude of your signal and determine the limits for vertical resolution.  For very small signals you may find that the noise you see begins to get large compared to the signal.
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• Change the signal form.  You may be able to show sine, square and triangular signals using your function generator.  If you can display a square wave signal, try to determine how quickly the signal changes.  It can't change instantaneously, and there will be some transient between voltage levels that you can see.  Consider whether that transient rise-time is due to the oscilloscope or the signal generator.  Or is this a situation where you can't tell what causes the effect?
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• Using a sine signal first, set the function generator for a 1KHz signal, then measure the actual frequency on the oscilloscope.  Your scope may have a built-in function for that, or you may have to check the length of a period using the horizontal scale setting.  It's probably best to have your scope set for .5 or .2 milliseconds/cm so that you can see a full period for a signal with a 1.0 millisecond period.
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      Now, you have used several of the standard test signals to learn your way about when using a scope.  Still, it's nice to have a real signal.  Here are two alternatives.

• Get a microphone and connect it to the oscilloscope vertical input terminals. It's easier to see things if you sing a musical note because that gives you a more-or-less periodic signal.  Try singing eee, aw and ooo into the microphone and observe the signals.  You may be able to get a reasonably nice sine wave signal with ooo.  If you do, you have a great future as a sine wave generator!

• Get a connector that will fit the speaker/headphone output of the sound card on the computer you're using - and you're using a computer if you're reading this.  Play a CD - one of your favorite songs - and observe the voltage output on the scope.  The author found a pair of very cheap headphones, about $1, and cut off the headphones and used the cord to do this.

• There will be a left channel and a right channel output.  Each channel goes to the phone for one ear.
• One channel wire will often be encased in a braided outer covering. The braided covering (metallic) should be connected to ground on the oscilloscope.
• Leave the other pair of wires from the headphone jack unconnected.
• Be careful that they do not short together, thus shorting the output from the sound board.
• Plug the jack into the sound board (line output if possible), and play a CD to observe the output signal.
• If you have a two channel scope, you can look at both channels simultaneously by connecting the other pair of output wires, to the input for the second channel on the scope.
• Be careful with the grounds to be sure that ground is connected to ground.

• You may be able to save your data in a computer file.  If your oscilloscope has a computer connection, investigate saving your data in a file.  There may be special programs on the computer to do that, and they are sometimes supplied by the scope manufacturer.
• Save your data in a flat file.  That could be a file with a txt or dat extension. A flat file doesn't have any formatting and just contains the characters that represent your data.  You can load a flat file into other programs for analysis. Programs you might use are Mathcad, Excel or Matlab.
• You can use FFT techniques to get the frequency content of the signal that you saved in a file.