The green version of the virtual sound card oscilloscope includes operating instructions, multimeter instructions, sound card settings and other files
This software uses a sound card for sampling and output. Whether the software can work properly is closely related to the correct settings of the sound card. The working mode of the sound card is 44100HZ, 16bit, two-channel duplex, and most sound cards support this standard.
Use of each part:
All virtual instruments are built on one panel, and the operation is very simple and intuitive.
1. Oscilloscope After starting the program, the oscilloscope is already in working status and has five working modes to choose from.
X single trace oscilloscope
X1,X2 dual trace oscilloscope
X1＋X2 Addition of two signals
X-Y two-channel signals are used for X-axis and Y-axis input respectively. This method is similar to the method of using Lissajous pattern to measure frequency in a general oscilloscope.
Frequency domain displays the spectral distribution of the signal
Various parameters of the oscilloscope can be adjusted through the above controls.
Press RECORD to save the input signal as a wav file, press it again to stop recording.
PAUSE can pause the oscilloscope screen for observation. Press it again to end the pause. Various parameters can still be adjusted during pause.
Save the screen You can save the oscilloscope screen as a bitmap file. You need to pause the screen first and adjust it before saving.
2. Frequency meter You need to press the power button to start the frequency meter.
The frequency is obtained by performing FFT on the input signal. It can be updated about 10 times per second, and the display error is about 10hz. If you want to get an accurate frequency value, you can use the output signal of the signal generator and the oscilloscope to measure it using the Lissajous figure method. If the number of FFT samples is increased, the error can be less than 1hz, but it will increase the amount of calculations, which seems unnecessary in practice.
3. Signal Generator You need to press the power button to start the signal generator. This is a dual-channel sine wave generator with very accurate frequency. Due to the limitations of sampling characteristics, the high-frequency part is distorted, but the waveform is quite good at 50hz-15khz. The output amplitude can be achieved by adjusting the volume. Press the left button to set the output frequency.
4. Multimeter This is an interesting accessory that requires pressing the power button to activate it. It can measure the effective value of resistance, capacitance, inductance and AC voltage. When measuring resistance, capacitance and inductance, you need to turn on the signal generator at the same time and select the appropriate output signal frequency. Connect the components under test and standard components to the circuit according to the schematic diagram. Press Enter Reference, enter the reference value, select the measurement method, and the value to be measured will be displayed on the LED screen.
Note: V(AC) can only measure the effective AC value. The oscilloscope window can display the waveforms of two signals at the same time, and you can see the relationship between amplitude and phase. The LED screen does not display a decimal point, so there are some techniques when entering the reference value. If the 0.047uf capacitor is used as the benchmark, you can enter 47 when inputting, and the unit of the displayed value will be the same as the benchmark value. The V (AC) position displays a relative value, which can be calibrated through an external potentiometer and a signal source with known amplitude. high speed download
An alternative application of signal generator: biofeedback mentality adjuster, which uses difference frequency to induce synchronous brain waves. Adjust the left channel signal to 400hz and the right channel to (400-d) hz. d=1-4: Promote sleep; d=4-8: Rich imagination, good inspiration, helpful for creative work; d=8-14: Can relax mental stress, overtired by mental work and need to rest The adjustment is very suitable; d=14-25; it is in a state of normal alertness and excitement, which is especially useful for normal mental work or to avoid drowsiness and missed work. The above can be found in the first volume of "Electronic News" 99, p153. The original article uses a single-chip microcomputer and complex circuits, and is implemented here using software. You can try it with headphones, the effect is pretty good.
The correct settings of the sound card are the prerequisite for the normal operation of this software. Due to the wide variety of sound cards and the numerous versions of drivers, the author cannot guarantee that every sound card will work properly. But through testing on two common sound cards, the software can work very well. The sound card chip tested is Yamaha 724, which uses the public version driver. The other one has an integrated sound card on the motherboard, and the chip is Innovation es1373, which uses the motherboard's own driver.
When setting up, roughly follow the following steps:
1. Open advanced sound control
2. Select the recording properties, open the recording volume control panel, and select LINE as the input method.
3． Turn off unnecessary sound effects, such as reverberation surround, to avoid left and right channels interfering with each other.
4. If there is a lot of background noise when there is no signal, try muting some options, especially CD audio.
5. Adjust the balance of output and input, which can be achieved with the help of the oscilloscope part and the signal generator part.
At this time, the signal is input from the LINE IN port. When outputting audio signals, there is no signal at the input port.
If you use other sound cards, you can refer to the above steps to set up. Be careful to use the public version of the driver or your own driver, and do not use the driver that comes with Windows. If it still doesn't work correctly, you can try another driver.
Possible situations:
There is no LINE IN port on the sound card, only a MIC port. This will happen on some cheap motherboard-integrated sound cards, because the MIC port is usually mono-channel, which means that the oscilloscope can only work with a single trace, and the multimeter can only measure voltage. .
Turn on the signal generator and the waveform will be displayed on the oscilloscope at the same time. This is caused by the output being fed back to the input. Various settings can be modified.
Cable production:
Connect a section of three-core shielded wire to the stereo plug to form a test cable, and use the same method to make another one. Plug them into the output and input ports on the back of the sound card, and the circuit is connected.
Software writing process:
The entire software is written in VC, and the API is used to operate the sound. Some parts such as FFT and bitmap saving are modified from the ready-made source code. I tried to use hardware to implement some functions, but after building the circuit and testing it, I found that this was completely superfluous. The software implemented it better than the hardware. It was difficult for the circuit to generate a standard sine wave, but the software could easily achieve it. This confirms the famous saying-simplicity comes first.
