The oscilloscope is one of the key instruments of any radio engineering laboratory for industrial use, as well as a conventional radio workshop. With the help of such a device, it is possible to determine malfunctions of electronic circuits, as well as to debug their work when designing new devices. However, the price of such devices is very high, and not every radio amateur can afford to buy such a little thing. This article is about how to make an oscilloscope from a computer. There are many ways to make such a device, but the basis is the same everywhere: the PC sound card serves as a card that will receive pulses, and a special adapter is attached to it. It serves to coordinate the levels of the measured signals and the input of the computer's audio card.
Computer Oscilloscope: Software
One of the main elements of the mentioned device is a program that visualizes the measured pulses on the monitor. There is a huge selection of such software, but not all utilities work stably. The Osci oscilloscope program from the AudioTester kit is especially popular among hams. It has an interface that looks like a standard analog device, there is a grid on the screen that allows you to measure the duration and amplitude of the signal. It is convenient to operate, and has a number of additional functions that programs of this type do not have. But each radio amateur will be able to choose the software that he likes best for work.
Technical details
So, in order to make an oscilloscope from a computer, it is necessary to assemble a special attenuator (voltage divider), which can cover the widest possible range of the measured voltage. The second function of such an adapter is to protect the input port of the sound card from damage that a high voltage level can cause. On most audio cards, the input voltage is limited to 1-2 volts. A computer oscilloscope has a frequency range limited by the capabilities of a sound card. For budget cards, it ranges from 0.1Hz to 20kHz (sinusoidal signal). The lower voltage limit that can be measured is limited by the level of background and noise and is 1 mV, and the upper one is limited by the adapter parameters and can be several hundred volts.
Voltage divider device
An oscilloscope from a computer has a very simple electrical circuit. It contains only two zener diodes and three resistors. The value of the resistors depends on the virtual oscilloscope scale used. This divider is designed for three different scales, with coefficients 1: 1, 1:20 and 1: 100. Accordingly, the device will have three inputs, to each of which a resistor is connected. The nominal resistance of the direct input resistor is 1MΩ. The common wire is connected through the reverse connection of two zener diodes. They are designed to protect the line input of the sound card from overvoltage when the switch is in the “direct input” position. Capacitors can be connected to the resistors in parallel, they will align the amplitude-frequency component of the device.
Conclusion
Such an oscilloscope is not elegant, but a simple circuit solution allows you to achieve a wide range of measured voltage. The mentioned device will help in the repair of audio equipment or can be used as a training measuring device.