AC SIGNALS-SIGNAL GENERATOR-OSCILLOSCOPE
AC SIGNALS:
Th signals with a constant value of amplitude are called "Direct Current" (DC) signals. Here the current flowing through the circuit has a fixed value.
However, there are signals that have a time varying amplitude. These are called "Alternating Current" (AC) signals. Pure AC signals are centered at 0 voltage level. The most common ones are; sinusoidal, square and triangular waves.
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| Sinusoidal waveform |
Va: peak voltage (max)
Vpp: peak to peak voltage (difference of between max and min)
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| Square waveform |
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| Triangular waveform |
The formula for sinusoidal wave is;
Sinusoidal: Vsinusoidal(t) = Va*sin(2*pi*(1/T)*t), where t is time variable. (Notice how voltage of sinusoidal is a function of time, t). Pi is pi (i don't know how to write 'pi'), the gradient which corresponds to 180 degree.
The important parameters are;
-T, Period : The duration for one cycle to finish. Unit is seconds.
-f, Frequency : The number of cycles within one second. It corresponds to f = 1/T . Unit is hertz or seconds^-1.
-Va, Peak Voltage : The maximum voltage point of the wave. Note that -Va is the minimum voltage point, hence it is another peak level (i.e. minimum and maximum peaks.) Unit is volts.
-Vpp, Peak to Peak Voltage : The voltage difference from minimum peak to maximum peak. For waves in figures it correspond to Vpp = 2*Va (i.e. it is from -Va to Va). Unit is Volts.
-Amplitude : It is the value of voltage for a wave at a specific time t. Amplitude can be any value in between -Va to Va.
Let's say we want to find the amplitude of the sine wave in figure 1 (a) at time t = 3T/8.
V(t=3T/8)=Va*sin(2*pi*(1/T)*(3T/8))=Va*sin(2*pi*(3T/8T))=Va*sin(2*pi*(3/8))
V(t=3T/8)=Va*sin((3*pi)/4), if pi is 180 degree then 3pi/4 is 135 degree.
V(t=3T/8)=Va*sin(135(degree))=0.707*Va
The application of AC voltages to the circuit is not actually different from DC voltages. The same rules (Ohm's rule, Kirchhoff laws, etc. ) all apply to them as well.
Signal Generator
Signal generator allows us to generate basic waveforms (sinusoidal, ramp, square, pulse) with any frequency and amplitude we desire.
The buttons and displays are shown is figure. Let's go over them. Power on/off switch turns on and off the device. Amplitude and Frequency buttons allows us to change the frequency and the amplitude of the signal. Of course once these selected, the new value is entered with the numeric pad. Adjustment knob is an alternative to the numeric pad for entering frequency values; however, we will use numeric pad more frequently. Under wave type buttons we choose the shape of our signal. Channel selection changes which is being displayed on the screen. Output enablers, as their name suggest, once clicked turns yellow and enables the regarding channel. The signal generator probes are connected to the Ch1&Ch2 probe outlets. Amplitude display shows the amplitude of the signal and frequency display shows the frequency of the signal.
The black end of the signal generator probe should be connected to the ground of the circuit. Please note that this device is not a measurement tool. It only generates waves. To measure AC signals we will use Oscilloscope.
Oscilloscope
Oscilloscope allows us to measure AC signals. It gives us the signal waveform within a certain time frame.
Let's go over the oscilloscope buttons and displays. The Menu On/Off button turns on and off the menu displayed on the screen. Menu display is the area where the menu is displayed on the screen.
Menu Sub-Keys are soft buttons that you choose over menu display. They have different application for different menu displays. Universal Knob is used for going through the menu display options. It provides an alternative to mMenu sub-keys. Vertical position knob changes the vertical position of the wave on the display. In other words the signal is shifted up or down as this knob is adjusted. the oscilloscope screen is gridded into 18x8 square. The vertical scalling knob is used for changing the vertical scalingof the 18 vertical squares. As it is adjusted the scaling of these squares increas or decreas. The scaling value is displayed on the Vertical Scaling display area. Horizontal position knob changes the horizontal position of the wave on the display. In other words as this knob adjusted, the wave is shifted left or right . The horizontal scaling knob is used for changing the scaling of 8 horizontal squares on the display. The value of horizontal scaling is displayed on the horizontal caling display area. Channel selection buttons are used for deciding which channel to be displayed. Once pushed these buttons turn yellow. Both channels can be displayed simultaneously (channel1 is yellow and channel2 is blue on the display). Trigger menu buttons opens the trigger sub-menu on the menu display area. Triggering is used for adjusting the frequency window of the oscilloscope display. If the trigger level and the channel wave are not on the same level then the wave on display will start to move. The trigger force button forces trigger to the selected channel level. Trigger knob is used for changing the level of the trigger. Auto set button is used for setting default scaling, position and triggering. Cursors menu opens the cursors sub-menu we can get automatic measurements on the display. So we can say cursors menu is used for manual measurement of the signal while the measure menu is used for getting automatic measurements. Math menu button opens the math menu on the display area. From here we can get the mathematical combinations of two channels on the display. Probe Comp. outlet is used for checking whether the probe is working or not. The probe's measurement end is connected here and the wave on the display is observed. If he wave is a 1kHz square wave then the probe is working fine.
V(t=3T/8)=Va*sin(2*pi*(1/T)*(3T/8))=Va*sin(2*pi*(3T/8T))=Va*sin(2*pi*(3/8))
V(t=3T/8)=Va*sin((3*pi)/4), if pi is 180 degree then 3pi/4 is 135 degree.
V(t=3T/8)=Va*sin(135(degree))=0.707*Va
The application of AC voltages to the circuit is not actually different from DC voltages. The same rules (Ohm's rule, Kirchhoff laws, etc. ) all apply to them as well.
Signal Generator
Signal generator allows us to generate basic waveforms (sinusoidal, ramp, square, pulse) with any frequency and amplitude we desire.
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| AATECH AWG1020 Arbitrary Signal/Waveform Generator |
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| Signal Generator Buttons and Displays Labelled |
The buttons and displays are shown is figure. Let's go over them. Power on/off switch turns on and off the device. Amplitude and Frequency buttons allows us to change the frequency and the amplitude of the signal. Of course once these selected, the new value is entered with the numeric pad. Adjustment knob is an alternative to the numeric pad for entering frequency values; however, we will use numeric pad more frequently. Under wave type buttons we choose the shape of our signal. Channel selection changes which is being displayed on the screen. Output enablers, as their name suggest, once clicked turns yellow and enables the regarding channel. The signal generator probes are connected to the Ch1&Ch2 probe outlets. Amplitude display shows the amplitude of the signal and frequency display shows the frequency of the signal.
The black end of the signal generator probe should be connected to the ground of the circuit. Please note that this device is not a measurement tool. It only generates waves. To measure AC signals we will use Oscilloscope.
Oscilloscope
Oscilloscope allows us to measure AC signals. It gives us the signal waveform within a certain time frame.
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| AATECH ADS-3202A Oscilloscope and Probes |
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| Oscilloscope Buttons, Knobs and Displays Labelled |
Menu Sub-Keys are soft buttons that you choose over menu display. They have different application for different menu displays. Universal Knob is used for going through the menu display options. It provides an alternative to mMenu sub-keys. Vertical position knob changes the vertical position of the wave on the display. In other words the signal is shifted up or down as this knob is adjusted. the oscilloscope screen is gridded into 18x8 square. The vertical scalling knob is used for changing the vertical scalingof the 18 vertical squares. As it is adjusted the scaling of these squares increas or decreas. The scaling value is displayed on the Vertical Scaling display area. Horizontal position knob changes the horizontal position of the wave on the display. In other words as this knob adjusted, the wave is shifted left or right . The horizontal scaling knob is used for changing the scaling of 8 horizontal squares on the display. The value of horizontal scaling is displayed on the horizontal caling display area. Channel selection buttons are used for deciding which channel to be displayed. Once pushed these buttons turn yellow. Both channels can be displayed simultaneously (channel1 is yellow and channel2 is blue on the display). Trigger menu buttons opens the trigger sub-menu on the menu display area. Triggering is used for adjusting the frequency window of the oscilloscope display. If the trigger level and the channel wave are not on the same level then the wave on display will start to move. The trigger force button forces trigger to the selected channel level. Trigger knob is used for changing the level of the trigger. Auto set button is used for setting default scaling, position and triggering. Cursors menu opens the cursors sub-menu we can get automatic measurements on the display. So we can say cursors menu is used for manual measurement of the signal while the measure menu is used for getting automatic measurements. Math menu button opens the math menu on the display area. From here we can get the mathematical combinations of two channels on the display. Probe Comp. outlet is used for checking whether the probe is working or not. The probe's measurement end is connected here and the wave on the display is observed. If he wave is a 1kHz square wave then the probe is working fine.
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