What is an oscilloscope?
An oscilloscope or CRO (cathode ray oscilloscope) is an electronic measuring device which provides a two-dimensional visual representation of a signal.
The upper part of the oscilloscope controls the time axis. The lower part controls the amplitude axis. The screen will show the waveform.
Parts of theoscilloscope:
Click on the symbol, drag and release on the desired position on the grid. The two terminals in the oscilloscope are the two channels on which the output waveforms can be seen.
The point at which output is to be seen is connected to a channel. As there are two channels, two waveforms can be viewed.
To open the oscilloscope,double-click on it or right–click and choose ‘Edit Properties’. It will open the following window.
The two channels are named channel 1 and channel 2. Channel 1 is shown in red and channel 2 in blue. The left channel is channel-1 and right channel is channel-2
1. Display for the waveforms: Each square is 1 cm x 1cm. The y-axis in display shows the variation in voltage and the x-axis shows the variation in time.
2. Power on/off.
3. X-Pos:Varying this you can adjust the position of the waveform in the x-axis.
4. Time-base control: By adjusting this knob you can set the time scale i.e. how many seconds or milliseconds in time domain should 1 cm in the display correspond to.
5. Frequency range setting: It should be on “Low” if the signal is in Hz or kHz and “High” if the signal is in MHz or GHz.
6. DC-AC-GND: Set to DC for all types of waveforms (even DCsignals). Set GND to connect the signal to ground. This would result in the signal becoming a straight line. You can then easily position the waveform to the any position on the display. Setting AC would connect a capacitor in series which would block out any dc component in the signal. So if you have an ac signal with a dc component which puts the waveform at say, 12 V, by using this setting you can bring the waveform back to the 0 V.
Waveform with DC switch on Waveform with AC switch on
7. Y-Pos:Varying this you can adjust the position of the waveform in the y-axis.
8. Quick Help: Click this button to see a brief explanation of all the options on theoscilloscope.
9. Close: Click to save and close the window.
10. Calibration controls: There are two buttons each for channel I and II. Clicking on this will show a sample square wave. This is generated inside the oscilloscope itself. It can be used to set the time base, amplitude control and other settings before connecting to the circuit.
11. Amplitude controls: By varying this you can adjust the amplitude scale i.e. how many volts or millivolts should 1 cm in the display correspond to.
How to measure amplitude, period and frequency:
· Amplitude: Measure the amplitude of the waveform in the display by counting the squares.Each square measures 1cm. So in the figure it can be seen that after positioning the waveform along the center-line of the display the amplitude of the signal is 3 cm. From the channel-1 amplitude scale it can be seen that scale is 2 V/cm. Thus the amplitude in volts is 2 x 3= 6 V.
· Period: The period is given as the time taken for one cycle. So now from display you can see that the x-axis (which corresponds to time) the distance between successive maxima or minima is 2 cm. From time-base scale it can be seen that each cm is 5 ms. So the period is found to be 2 x 5= 10 ms.
· The frequency is the number of cycles per second. Since we know the time taken for a single cycle-period- the number of cycles in one second is 1/period. Thus the frequency of the signal is 1/10 ms= 100 Hz.
What do I do to view the output?
· Double-clickon the oscilloscope to open it.
· Vary the time base to adjust the scale of the wave in the x-axis.
· You can use the X-Pos and Y-Pos to adjust the position of the wave.
· Similarly vary the amplitude scale to adjust the scale of the wave in the y-axis. Be aware of which amplitude knob will control which wave.