How to make an oscilloscope from the computer with your own hands?
Quite often lately, instead of making, for example, an oscilloscope from a computer, many people prefer to simply buy a digital USB oscilloscope. However, having walked around the market, it can be understood that in fact the cost of budget oscilloscopes starts from about $ 250. And more serious equipment has a price several times more.
It is for those people who are not satisfied with such a cost that it is more relevant to make an oscilloscope from a computer, especially since it allows you to solve a large number of tasks.
What should I use?
One of the most optimal options is the Osci program, which has an interface similar to a standard oscilloscope: there is a standard grid on the screen, with which you can independently measure the duration, or the amplitude.
Among the drawbacks of this utility, it can be noted that it works somewhat unstably.In the course of its work, the program can sometimes hang, and in order to reset it later, you will need to use the specialized Task Manager. However, all this is compensated for by the fact that the utility has a familiar interface, is quite user-friendly, and also has a rather large number of functions that allow you to make a complete oscilloscope from a computer.
On a note
Immediately, it is worth noting that the set of these programs has a specialized low-frequency generator, however, its use is extremely discouraged, as it tries to completely regulate the operation of the audio card driver, which can provoke an irreversible mute. If you try to use it, make sure that you have your own recovery point or the ability to backup the operating system. The best option for how to make an oscilloscope from a computer with your own hands is to download a normal generator, which is located in the "Additional Materials".
Avangard is a domestic utility,which does not have a standard and usual measuring grid, and also differs in a too large screen for taking screenshots, but it also provides the ability to use the built-in amplitude amplitude voltmeter, as well as a frequency meter. This allows you to partially compensate for the disadvantages that were indicated above.
Having made such an oscilloscope from a computer with your own hands, you may encounter the following: at low signal levels, both the frequency meter and the voltmeter can greatly distort the results; quite acceptable. Another useful feature of it is that it is possible to carry out a completely independent calibration of the two already existing scales of the built-in voltmeter.
How will it be used?
Since the audio circuit's input circuits have a dedicated coupling capacitor, a computer as an oscilloscope can only be used with a closed input. That is, only the variable component of the signal will be observed on the screen, however, having some dexterity, with the help of these utilities it will also be possible to measure the level of the constant component.This is quite relevant if, for example, the counting time of the multimeter does not allow to fix a certain amplitude value of the voltage on the capacitor, which is charged through a large resistor.
The lower voltage limit is limited by the noise and background levels and is approximately 1 mV. The upper limit has limitations only on the parameters of the divider and can reach even a few hundred volts. The frequency range is directly limited by the capabilities of the audio card itself and for budget devices it is approximately from 0.1 Hz to 20 kHz.
Of course, in this case, a relatively primitive device is considered. But if you do not have the opportunity, for example, to use a USB oscilloscope (prefixed to a computer), then in this case its application is quite optimal.
Such a device can help you in repairing various audio equipment, and can also be used solely for training purposes, especially if you supplement it with a virtual LF generator. In addition, an oscilloscope program for a computer will allow you to save a plot for illustrating a certain material or for posting on the Internet.
If you need a prefix to a computer (oscilloscope), then it will be a little more difficult to make it. At the moment, on the Internet you can find a sufficiently large number of different schemes for such devices, and to build, for example, a two-channel oscilloscope, you will need to duplicate them. The use of the second channel is often relevant if you need to compare two signals or a computer prefix (oscilloscope) will also be used with an external synchronization connection.
In the majority of cases, the schemes are extremely simple, however, in this way you will be able to provide a fairly wide range of voltages available for measurement on your own using the minimum number of radio components. In this case, an attenuator, which is built according to the classical scheme, would require you to use specialized high-resistance ohms, and its input resistance would constantly change if the range was switched. For this reason, you would experience certain limitations in using standard oscilloscopic cables, which are calculated for an input impedance of no more than 1 mΩ.
We provide security
To ensure that the line-in input of the audio card is protected from the possibility of accidental high voltage, you can install specialized zener diodes in parallel.
With the help of resistors you can limit the current of the zener diodes. For example, if you are going to use your oscilloscope computer (generator) to measure a voltage of about 1000 volts, then in this case you can use two single watt or one two watt resistor as a resistor. They differ among themselves not only in their power, but also in terms of how much the voltage in them is the maximum permissible. Also worth noting is the fact that in this case you will need a capacitor, the maximum allowable value for which is 1000 volts.
Often you need to initially look at the variable component of a relatively small amplitude, which in this case may differ in a rather large constant component. In this case, on the oscilloscope screen with a closed input there may be a situation where you will not see anything except the variable component of the voltage.
Choosing a voltage divider resistors
Due to the fact that quite often modern radio amateurs have certain difficulties in order to find precision resistors, it often happens that you have to use standard wide application devices that need to be adjusted with maximum precision, since you can’t make an oscilloscope from a computer otherwise will come out.
In most cases, high-precision resistors are several times more expensive than conventional ones. At the same time, today they are most often sold immediately by 100 pieces, and therefore their acquisition can not always be called expedient.
In this case, each divider arm consists of two resistors, one of which is constant, while the other is a trimmer. The disadvantage of this option is its cumbersome, but the accuracy is limited only by what available parameters has a measuring device.
We select resistors
The second option to make a computer as an oscilloscope is to pick up a pair of resistors. Accuracy in this case is ensured by the use of pairs of resistors from two sets with a sufficiently large scatter.Here it is important to initially make a thorough measurement of all devices, and then choose pairs, the sum of the resistances of which is the most appropriate for the circuit you are performing.
It is worth noting that this method was used on an industrial scale in order to adjust the divider resistors for the legendary TL-4 device. Before you make an oscilloscope from the computer with your own hands, you need to examine the possible disadvantages of such a device. First of all, it can be noted the complexity and the need to use a large number of resistors. After all, the longer the list of devices you use is, the higher the final accuracy of the measurements will be.
It is worth noting that the fitting of resistors by removing part of the film today is sometimes used even in modern industry, that is, in this way an oscilloscope is often made from a computer (USB or some other).
However, it is immediately worth noting that if you intend to fit high-resistance resistors, then in this case the resistive film should in no case be cut through.The thing is that in such devices it is applied on a cylindrical surface in the form of a spiral, therefore, it is necessary to make a filing very carefully to eliminate the possibility of breaking the chain.
If you do the oscilloscope from the computer with your own hands, then in order to carry out the adjustment of the resistors at home, you just need to use the simplest sandpaper, "null."
- Initially, the resistor, which has obviously less resistance, must be carefully removed with a protective layer of paint.
- After that you should solder the resistor to the ends, which will be glued to the multimeter. By performing careful movements with an emery paper, the resistance values of the resistor are brought to a normal value.
- Now, when the resistor is finally fitted, the place to cut should be covered with an additional layer of specialized protective varnish or glue.
At the moment, this method can be called the most simple and fast, but it also allows you to get good results, which makes it optimal for work at home.
What you need to consider?
There are a few rules that need to be observed in any case, if you are going to carry out such work:
- The computer you are using must be reliably grounded.
- In no situation should you stick an earthen wire into the socket. It connects through a specialized case of a linear input connector to the case of a system unit. In this case, regardless of whether you are going to zero or to the phase, you will not have a short circuit.
In other words, only a wire can be plugged into the socket, which is connected to a resistor, which is located in the adapter circuit and has a rating of 1 meg. If you are trying to plug a cable into the network that connects to the case, then in almost all cases this leads to the most unpleasant consequences.
If you use the Avangard oscilloscope, then in the calibration process you should select the scale of the voltmeter “12.5”. After you see the mains voltage on your screen, you need to enter the value 311 in the calibration window. At the same time, it should be noted that the voltmeter then shows you the result in the form of 311 mV or close to it.