A complete guide to using an oscilloscope in the workshop: instrument types, waveform reading, horizontal and vertical divisions, time and voltage scales, practical examples of sensors, actuators, and CAN lines. Designed for mechanics, auto electricians, and diagnosticians looking to take their electronic diagnostics to the next level.

Read also: OSCILLOSCOPE - COMPLETE GUIDE: SETTINGS, CONNECTIONS, MEASUREMENT STRATEGIES AND REAL-WORLD CASES

Automotive OSCILLOSCOPE 2026: A COMPLETE GUIDE TO MEASUREMENTS AND DIAGNOSIS

Updated on November 13, 2025 · By the Autoricambi Tritella technical team

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🔧 INTRODUCTION: WHY THE OSCILLOSCOPE IS ESSENTIAL IN THE WORKSHOP TODAY

In the modern workshop, a multimeter is no longer enough. Control units, sensors, actuators, CAN bus, and PWM signals operate with extremely fast pulses that a traditional tester cannot "speak."

This is exactly what an automotive oscilloscope does: it displays the signal over time , allowing you to see peaks, dips, pulses, disturbances, and response times. In practice, it makes visible what the control unit is actually doing, not just what the diagnostics "tells" in words.

If you want to make professional-level diagnoses , distinguish a faulty sensor from a broken wiring or a control unit that is not driving correctly, the oscilloscope becomes the main tool on your workstation.

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📡 TYPES OF AUTOMOTIVE OSCILLOSCOPES

Over time, several generations of oscilloscopes have emerged. Understanding the differences helps you choose the right instrument for your workshop.

1️⃣ Analog oscilloscopes (cathode ray tube)

These are the "historical" instruments: a cathode ray tube, an electron beam, and a continuous image on the screen. They display the waveform in real time well, but:

• they have no memory or very little;
• they are bulky and require mains power;
• They do not allow you to save and print signals.

Today they have more educational value than practical value in the workshop.

2️⃣ Hybrid / Semi-digital Oscilloscopes

They still combine the cathode ray tube with an electronic control unit. They were a bridge to digital, but have now been overtaken by the new generation of LCDs.

3️⃣ Portable digital oscilloscopes

These are the ones that are really interesting for the automotive industry :

• liquid crystal display (LCD) with good definition;
• compact size, often powered by 12 V or internal battery;
• very fast sampling, also suitable for pulses of a few microseconds;
• memory to save waveforms and review them later;
• PC connection for analysis, report printing and archiving.

These tools are intended for low voltage electronic signals found in modern vehicles: injection, ignition, sensors, actuators, CAN, LIN, etc.

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🖥️ SCREEN, GRID AND DIVISIONS

An oscilloscope's screen is divided into a grid called a graticule , made up of regular squares called divisions . Each division represents a time value (horizontal) and a voltage value (vertical).

In digital oscilloscopes, the grid is actually made up of dots (pixels) . The instrument measures the signal in many closely spaced samples and represents them by connecting them as a continuous line. The higher the sampling rate, the more faithful the drawn signal is to reality.

How is the screen structured?

• Vertically there are usually 8–10 divisions .
• Horizontally approximately 10 divisions.
• Each division can be worth, for example, 1 V, 2 V, 5 V… or 1 ms, 5 ms, 50 µs etc.

Understanding divisions is crucial because every measurement on the oscilloscope is made by counting how many squares the signal occupies and multiplying by the set scale.

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⏱️ HORIZONTAL (TIME) AND VERTICAL (VOLTAGE) SCALES

All oscilloscopes have at least two main scales :

• Time scale (horizontal axis) : Expressed in seconds, milliseconds, or microseconds per division (s/div, ms/div, µs/div). Typically ranges from 50 µs to 50 s per division.
• Voltage scale (vertical axis) : expressed in Volts per division (V/div). In automotive diagnostics, it is typical to work from 50 mV up to 100 V , depending on the signal.

Rule of thumb for time (horizontal)

Rule of thumb: The main signal you're interested in should occupy 70–80% of the screen . If it's too narrow, reduce the time/div; if it's squashed to one side, increase the time/div.

Rule of thumb for tension (vertical)

Here too, the signal must be clearly legible. A scale that's too high (e.g., 50 V/div for a lambda probe) will result in a nearly flat line. A scale that's too low will "clip" the signal and cause it to disappear from the screen.

Reading currents with a clamp meter

If you connect a clamp meter to an oscilloscope , it converts the current into a voltage signal (for example, 100 mV = 1 A). In this case, the vertical scale no longer represents Volts but Amperes per division , based on the clamp's conversion factor.

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📈 HOW TO READ AND INTERPRET WAVEFORMS

Once the scales are set correctly, the instrument draws the waveform . This is where the diagnostician's experience comes into play.

Pulse waveforms

Many automotive signals are a sequence of pulses (e.g., injectors, rpm sensors, CAN). Without an oscilloscope, you'd only see an "average" voltage on the multimeter; on the screen, however, you can distinguish:

• peak height (driving voltage);
• pulse width (injection time, PWM duty cycle);
• any falls or ailments.

Analog signals

Lambda probes, MAP sensors, TPS, temperatures: these are continuously varying signals. The oscilloscope allows you to evaluate response speed , any gaps, noise, and interference that the tester misses.

Sampling and digitization

In digital models, each trace is the result of thousands of "photographs" of the signal, one after the other. If the sampling is too slow compared to the signal, you risk seeing a false or simplified waveform. For this reason, when working on CAN or injectors, it is important to use appropriate settings recommended by the instrument manufacturer.

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🚗 PRACTICAL APPLICATIONS ON MODERN CARS

Let's look at some typical applications of the oscilloscope in the workshop.

1️⃣ Engine speed sensor (CKP)

• Time scale: 5–10 ms/div
• Voltage range: 5–10 V/div (inductive sensors) or 2–5 V/div (Hall)

The waveform should be regular, with no missing teeth or drops. A bent tone tooth, faulty wiring, or a weak sensor is immediately visible.

2️⃣ Petrol/diesel injectors

• Time scale: 1–2 ms/div
• Voltage range: 20–50 V/div (traditional system), different values ​​for piezoelectrics with dedicated probes

You can measure the trip time, see the opening peak, the holding phase and the return wave that confirms the state of the internal coil.

3️⃣ Ignition coils

With suitable probes, you can see high voltage peaks, spark duration, and any cuts caused by faulty cables, spark plugs, or ECUs.

4️⃣ CAN bus and communication networks

Modern digital oscilloscopes, with times on the order of microseconds, allow CAN to be analyzed as a high-speed differential signal. This is the best way to identify:

• interruptions or short circuits;
• oxidized terminals;
• lines that reflect or distort the signal.

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🛠️ MISTAKES TO AVOID AND PROFESSIONAL ADVICE

• Always solid ground: Connect the oscilloscope's ground to reliable chassis points, not to painted screws or dirty parts.
• Use quality probes: low-quality alligator clips, tips, and extension cables introduce resistance and capacitance that alter the signal.
• Don't rely solely on the autoscale: the automatic function can help, but for serious measurements it is better to manually set the time and voltage.
• Save waveforms: Use the memory and PC connection to save solved cases and use them as an internal “database” in the workshop.
• Always compare to a healthy vehicle: When possible, measure the same signal on an identical, working car.

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❓ FREQUENTLY ASKED QUESTIONS

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📌 CONCLUSIONS

The oscilloscope isn't just another tool, but the heart of modern diagnostics . It allows you to determine whether the problem is mechanical, electrical, electronic, or software, before you even begin replacing parts.

Learning to use it correctly—understanding the grid, divisions, time and voltage scales —means drastically reducing troubleshooting times, increasing the reliability of repairs, and giving your workshop a professional image in the eyes of the customer.

If you want to take your workshop diagnostics to the next level, the first concrete step is one: turn on the oscilloscope and start using it every day , not just when you “don't know what to look at anymore”.