Every amateur radio in his home laboratory must be a device, such as an oscilloscope.It is required for repair and adjustment of electronic circuits.Furthermore, without said device does not manage the study of new circuits and their properties.However, the cost of digital or analogue oscilloscope quite high.You can try to find the device used, but these devices are not everyone can afford.This article focuses on how to make the oscilloscope of the sound card.The price of such alteration is negligible, because the device is taken as a basis for the said item PC.To display the waveform using special software.
oscilloscope sound card: the advantages and disadvantages
The advantages of the device under consideration include low cost, of course, except for the computer itself.Now the drawbacks.Outset: there will be more than merit.The main disadvantage, which is characterized by an oscilloscope of the sound card - this is a very high sensitivity.It responds to even interference, resulting waveform may have errors.A second drawback is the fact that the input interface of the sound card is able to withstand the signal amplitude does not exceed 2 V. This means that the card can easily be damaged.This deficiency should be considered in the manufacture of the adapter.The oscilloscope of the sound card is not able to measure DC voltage.
How do Adapter
The first thing to take into account the input level of the sound card, most often it is less than two volts, and in some boards - no more than one volt.Naturally, for the measurement of this amplitude is insufficient.This requires the adapter, which will increase the signal amplitude limits.Software - Oscilloscope - has two permissible level measurements: 12.5 V and 250 V. The concept of such a device includes a total of six elements - resistors.R1 and R2 have a nominal resistance of 1.5 MW, R3 and R4 - 75 ohms, R5 and R6 - 1,5 kW.Power dissipation resistor should not be less than 0.5 watts.The circuit has a 5-pin inlet (two - from the signal source 250, two - from 12.5 and the fifth - the general - wire) and three output at the output connected to the line input of the sound card (left and right channels and overall).
proceed to describe the concept of the adapter.The first pair of inputs - "source 250" - is connected to resistors R1 and R2, further - with R3 and R4;at the output terminal, respectively, left and right line input.The second pair, "source 12.5" connected "in the gap" between the resistors, that is one conclusion - between R1 and R3, and the second - between R2 and R4.And finally, the last, the total output goes to the line-in connector sound card.It is associated with the left and right channels through resistors R5 and R6, connected after a pair of resistors R3 and R4.In order to reduce the impact of noise on the device, you must place the adapter board in a metal enclosure.That's the whole oscilloscope.The sound card receives incoming signals and the software displays waveforms on the computer monitor.
Setting Up To adjust the oscilloscope of the sound card, you must go to mixers and PC turn off gain on the microphone, set the volume level is below average.The resulting measuring device capable of quite clearly draws the waveform of low frequency, as well as to determine the frequency of the signal.
