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university:courses:electronics:electronics-lab-speaker [23 Aug 2019 14:07] – Antoniu Miclaus | university:courses:electronics:electronics-lab-speaker [06 Sep 2019 14:31] – replaced Z plot Pop Andreea | ||
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1 - Loudspeaker, | 1 - Loudspeaker, | ||
- | ===== Directions :===== | + | =====RMS Voltage measurement===== |
+ | ====Hardware Setup==== | ||
Build the circuit shown in figure 2, preferably using your solder-less breadboard. The loudspeaker can be in an enclosure or not. | Build the circuit shown in figure 2, preferably using your solder-less breadboard. The loudspeaker can be in an enclosure or not. | ||
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{{ : | {{ : | ||
- | <WRAP centeralign> | + | <WRAP centeralign> |
- | Connect waveform generator 1, and the two scope channels to the loudspeaker circuit as shown. | + | {{ : |
+ | <WRAP centeralign> | ||
+ | \\ | ||
+ | ====Procedure==== | ||
- | =====Procedure: | + | In Scopy, start the Signal generator and generate a sine waveform with 8V peak-to-peak amplitude and 100 Hz frequency. |
- | Start the Scopy software. Select | + | Start the Voltmeter and set both channels to AC (20Hz-800Hz). Using the Voltmeter tool we can calculate |
+ | Try setting | ||
- | A few words on why these setting should be adjusted. As the frequency is swept the AWG output is stopped briefly between frequency steps and the signal driving the speaker will be turned off. The speaker is a mechanical system with resonance and this step change in the driving signal will cause it to ring at the resonate frequency. In order to make an accurate measurement at the driving frequency we must wait for the ringing to die out. The amount of time needed will depend on the particular speaker being measured. The 40 mSec suggested above was the correct value for the speaker used in this example. Your results may vary depending on your particular speaker. Switching to the cosine window function gives a more accurate amplitude result. | + | {{ : |
+ | <WRAP centeralign> | ||
- | Hit the Run button. | + | You can plot the calculated impedance Z vs Frequency. The frequency of the signal generator is set in steps of 100 Hz and for each frequency you compute Z. The speaker impedance |
+ | \\ | ||
- | <WRAP centeralign> | + | {{ : |
- | You can now Export the data, as gain not in dB to make the math easier, to a comma separated values file and load it into a spreadsheet program such as Excel. | + | <WRAP centeralign> |
- | By saving | + | =====Frequency Response===== |
+ | ====Hardware Setup==== | ||
+ | In order to plot the frequency response make the connections as shown in Figure 6. | ||
+ | {{ : | ||
+ | <WRAP centeralign> | ||
+ | \\ | ||
+ | ====Procedure==== | ||
+ | In the Network analyzer tool you will do a logarithmic sweep. | ||
- | {{ : | ||
- | Where:\\ | + | {{ :university: |
- | G<sub>1</ | + | |
- | G< | + | <WRAP centeralign>Figure 7: Frequency sweep of the loudspeaker circuit</WRAP> |
- | A is the AWG amplitude\\ | + | |
- | You can calculate the magnitude of the speaker impedance is by dividing the channel 1 voltage gain by the channel 2 voltage gain all multiplied by the 100Ω resistor. An example plot is shown in figure 4. Your speaker will probably look much different than this. | ||
- | {{ : | ||
- | <WRAP centeralign> | ||
- | The speaker impedance is very close to 8Ω in the linear region but is much higher at the resonance frequency F< | ||
===== Questions: ===== | ===== Questions: ===== | ||
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http:// | http:// | ||
- | **Return to Lab Activity [[university: | + | <WRAP round download> |
+ | **Lab Resources: | ||
+ | * Fritzing files: | ||
+ | * LTSpice files: | ||
+ | </ | ||
+ | |||
+ | |||
+ | |||
+ | **Return to Lab Activity [[university: | ||