What is an Oscilloscope?

Types of oscilloscopes

The oscilloscope is an electronic measuring instrument for the visualization of variations in the electrical voltage over time. The history of creation began in the last decades of the 19th century at the origin of electronics initially as a part of physics. It can be said that the further evolution of electronics as an independent science is due to the simultaneous development and improvement of the oscilloscope. In practice, it is the most versatile measuring and diagnostic device in the world of electronics.

In the case of a typical voltmeter, we have an observation of the instantaneous value of the measured voltage (averaged over some period in time) and shown on the screen simply as a number. In other words, each voltmeter (or similar measuring instrument) can be regarded as one-dimensional or uniaxial that is showing only the measured magnitude of a given quantity. However, in the case of an oscilloscope, we have a second dimension (or axis) - the axis of time. Therefore, we can depict not only the instantaneous value of the electrical voltage but also its evolution in time. The picture of a simple one-dimensional numerical value becomes two-dimensional. An exact shape of the signal time variations (so colled oscillogram) can be built. It is always assumed the horizontal axis (x) on the screen is the time dimension, and the measured voltage is shown along the vertical axis (y).

From the user point, every oscilloscope consists of four sections: the display, vertical section, horizontal section, and trigger. The vertical section controls the amplitude of the displayed signal, while the horizontal section controls the time base or sweep of the instrument. The trigger section runs the start event of the sweep.

Depending on the type of measured input signals, the oscilloscopes can be seen as analog or digital. On the other hand, depending on their internal architecture, they can be divided into two types: old, classic ones with pure analog electronics and Cathode Ray Tube (CRT) display and modern digital oscilloscopes (Digital Storage Oscilloscopes, DSO) with both analog and digital electronics, internal memory for data storage and processing, microprocessor control and Liquid Crystal Display (LCD) screen. Depending on their performance, they are desktop, portable (battery-powered or handheld), or PC-based. The latter is a set of external devices and a software program for managing and displaying measurements on the computer screen. The communication between the device and the computer is through a standard digital interface, most commonly USB, LAN, or Wi-Fi.

Read in more details about different types of digital interfaces used in modern car scopes.

Depending on their purpose, oscilloscopes are divided into universal digital storage oscilloscopes used for general measurements in electronics, and specialized ones designed for specific tasks in various fields of engineering and industry. Oscilloscopes used in vehicle diagnostics, so-called engine tester scopes, are intended to monitor the ignition circuits of the internal combustion engines. They are a typical example of specialized oscilloscopes.

Of course, using an oscilloscope any parameter can be measured, not only the electrical voltage. In this situation, the parameter should be transformed into voltage by using special hardware called transducer. A typical example is the current clamp, which measure the current in the primary ignition circuit of the vehicle.

The modern digital oscilloscope is a complex and versatile tool, and its successful use requires a considerable amount of time to study the principle of its operation and capabilities. Achieving a satisfactory level of working with it is not an easy task and should not be underestimated. It requires sufficient responsibility, patience, and professional skills.

See the basic features and technical specifications of our automotive scilloscopes BOSA-02 and BOSA-04.

Automotive diagnostic oscilloscope

In modern vehicle service diagnostics, a specialized oscilloscope called engine tester scope is used. The advantage of that scope is its ability to take precise measurements of short signals but having periods tens and even hundreds of times longer than the signal itself. An example of such a signal is the secondary ignition voltage in gasoline engines.

Let's as an example take the ignition process in the four-cylinder gasoline engine. The ignition spark generation with subsequent fuel burning and fading oscillations takes approximately 2 ms. With the engine idling typically with 800 rpm, the spark and burning of the next in order cylinder will occur after 37.5 ms, of the next cylinder again after 37.5 ms and so on. All four strokes (2 full crankshaft turns) will take approximately 150 ms. And here it is become clear, in order to see the ignition process of all four cylinders simultaneously on the oscilloscope screen, the measurement duration should be at least 200 ms (in the technical world of measurement tools it is tradition to change input ranges in steps multiple of 1-2-5). So, on the display we will have a 200 ms picture with the burning in each of the four cylinders taking 2 ms only or 1% of the full screen. Obviously, if we want to see all ignition sparks at the same time using an universal oscilloscope, we will see only four sharp needles without any details.

Specialized automotive diagnostic oscilloscopes have built-in algorithms that can solve the above situation. Based on the particular ignition pattern and the order of individual cylinders, engine testers collect high-resolution data only in the moments around the ignition and show simultaneously on the screen the ignition in the cylinders for one complete cycle.

Read about ignition patterns observation using Sparkskope diagnostic mode.

Find out more about all measuring capabilities and operating modes of our automotive diagnostic software SudioBOSA.

Besides the advantages described in the above example, the specialized automotive oscilloscope also has all the necessary capabilities to test the operation of the various types of sensors and circuits in the vehicle. Frequently, engine testers are also equipped with the appropriate algorithms for self-analysis and automatic calculation of the required parameters in the diagnostic process.

You can read more about modern car diagnostics and oscilloscope use on our library page.