Oscilloscopes: Your questions, our answers.

Immerse yourself in the world of oscilloscopes and deepen your knowledge. Our experts are ready to shed light on all facets of oscilloscope use with you.

What bandwidth does my oscilloscope need?

The required bandwidth is determined by the highest signal frequency to be measured. If the bandwidth is set too low, the oscilloscope cannot detect any high-frequency changes. The amplitude may be distorted, and the edges are difficult to see, so that signal details are lost. When analysing analogue signals, the specified oscilloscope bandwidth should be at least three times as large as the highest sine wave frequency. When analysing digital signals, we recommend a bandwidth of five times the highest clock frequency to be measured.

Attention: The measuring system consists not only of the oscilloscope, but usually also of a probe. Both together form the relevant system bandwidth.

What does "sample rate" mean for an oscilloscope?

In an oscilloscope, the sample rate refers to the number of measuring points per unit of time with which the oscilloscope's A/D converter converts the analogue signal input values into digital data (samples per second, Sa/s). The higher the sample rate, the better the temporal resolution and thus the details recognisable in the signal curve. For oscilloscopes with more than one channel, the sample rate may be reduced if several channels are used. With a longer time base setting, the sample rate is reduced according to the available memory depth.

What does "signal acquisition rate" mean for an oscilloscope?

The signal acquisition rate indicates the speed at which the measuring device acquires a signal (specified in waveforms per second, wfms/s). The number of detections depends, among other things, on the set time resolution (seconds per scale division) and the memory depth. An oscilloscope requires a certain amount of time to process the data after each sampling cycle. The shorter this processing time is, the faster the oscilloscope resamples a signal and can therefore detect sporadic signal anomalies more quickly, for example. With multi-channel oscilloscopes, the signal acquisition rate may be reduced if several channels are in use.

How much memory does my oscilloscope need?

The number of scans is limited by the memory depth: To be able to utilise the maximum sampling rate for a longer time range, you need a large memory. The memory requirement is calculated using a simple formula: storage depth = recording duration x sampling rate. However, this only applies if each input channel of the oscilloscope has the same memory depth. For sporadic signal events, it is advantageous to have a memory as deep as possible and a high signal acquisition rate to be able to store as many signal sequences as possible.

How fast should the rise time of an oscilloscope be?

The rise time of an input signal (edge steepness) is the time it takes for the signal to transition from 10 to 90 % of the maximum amplitude. The rise time of the oscilloscope should be one third to one fifth of the rise time of the signal to be measured. An oscilloscope with a higher rise time can capture important details of fast transitions more accurately. The steepest possible edge is particularly important when recording digital signals, e. g. pulse signals.

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What is an Oscilloscope Probe?

An oscilloscope probe provides a physical and electrical connection between a test point and the oscilloscope. It can transmit the signal 1:1 or attenuate it (10:1) to safely measure higher voltages. The probe has a high input impedance to minimize the load on the circuit being measured and to ensure that the signal remains undistorted. Probes are often shielded to reduce electromagnetic interference and to ensure that the signal is transmitted clearly and accurately to the oscilloscope. Depending on their type, probes can be designed for various applications, such as measuring high-frequency signals, current, or differential signals.

What is a Passive Probe?

Passive probes are the most common type of probes for oscilloscopes. They do not contain active components such as amplifiers or electronic circuits and can be operated without power from the oscilloscope. Due to their simple design, passive probes are very robust and less prone to damage. They are included with most oscilloscopes. There are different types of passive probes, the most common being 1:1 and 10:1 probes. 1:1 probes transmit signals without attenuation and have an input impedance of about 1 MΩ. Because they are very sensitive, 1:1 probes can more easily detect small signals. 10:1 probes attenuate the signal by a factor of 10, which increases the inpu

What is an Active Probe?

Active probes for oscilloscopes contain amplifiers and other electronic components that provide extremely high input impedance (over 1 GΩ) and very low capacitive loading. They are characterized by high bandwidth (up to several GHz) and high precision, making them ideal for measuring fast and high-frequency signals. Due to the built-in electronics, they deliver a better signal-to-noise ratio, but they require external power and are more expensive than passive probes.

What are Switchable Probes?

Switchable probes are special oscilloscope probes that feature the ability to change the attenuation factor. A switch allows you to toggle between settings, such as 1:1 and 10:1. Switchable probes are particularly useful in applications where frequent changes between different signal levels are necessary or when versatile measurement capabilities are desired without the need to use multiple probes. If the oscilloscope does not automatically recognize the probe attenuation, the user must manually adjust the settings on the oscilloscope.

What is Automatic Probe Recognition?

Automatic probe recognition is a feature of modern oscilloscopes that allows the device to automatically identify which probe is connected. By identifying the type of connected probe (e.g., 1:1, 10:1, active probe), the oscilloscope adjusts its settings, such as the specific attenuation factor, accordingly. This reduces error rates and simplifies operation. In addition to the attenuation factor, other information such as bandwidth, impedance, and maximum input voltage can also be automatically recognized and considered. Some systems also perform automatic calibrations and compensations to ensure that measurements are accurate and signal quality is optimal.

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What is the vertical sensitivity?

The vertical sensitivity describes how much the oscilloscope can amplify a weak input signal before it is displayed on the screen. It is usually specified in millivolts per scale division (mV/div). For example, if the vertical sensitivity is set to 5 mV/div, this means that each vertical division on the screen represents a voltage of 5 millivolts. The correct setting of the vertical sensitivity is important to display the signal precisely on the screen. If the sensitivity is too high, the signal may be overdriven and if it is too low, the display may be too weak or inaccurate.

How can I measure the current with an oscilloscope?

Special current probes are available for measuring current with an oscilloscope. A so-called Rogowski coil or a Rogowski current transformer is used for alternating current measurement. Rogowski current transformers are robust and enable AC measurements up to 100 kA. Oscilloscope current clamps are ideal for direct current measurements. These are generally suitable for currents up to 2 kA. Alternating current measurement is also possible, but only up to 100 MHz. Oscilloscope current clamps are available as accessories.

What purchasing criteria should I consider when choosing an oscilloscope?

The criteria for purchasing an oscilloscope include technical requirements and specifications as well as budgetary conditions and company-specific purchasing conditions. Your measurement application defines the technical properties of the oscilloscope. Depending on the budget, compromises may have to be made when purchasing. However, these compromises should not affect the decisive parameters. The 12 most important purchase criteria for an oscilloscope are:

Bandwidth
Number of channels
Vertical resolution
Sample rate
Rise times
Compatibility (probes etc.)
Trigger functions
Memory depth
Automated measurement functions
Simple operation
Expansion options
Interfaces

How many channels does my oscilloscope need?

The measurement application determines how many channels an oscilloscope requires. As a rule, 2 to 4 analogue channels are sufficient for simple signal analysis. For very complex applications, 8 input channels can be useful, for example to monitor several sensors and actuators simultaneously. For example, 8-channel oscilloscopes are used to analyse the alternating current of electric motors by measuring the current and voltage on the three phases (= 6 channels) and the remaining 2 channels are available for trigger conditions. An oscilloscope requires additional digital input channels for the validation of digital and mixed signals.

Why is user-friendliness important for an oscilloscope?

A high level of user-friendliness is important for several reasons:

Efficiency: A high level of user-friendliness enables the user to access the desired functions and settings quickly and efficiently. This saves time and makes it easier to carry out measurements.
Reliability of results: An intuitive user interface reduces the risk of operating and measurement errors. Clear instructions, a well-organised menu structure and well-placed controls help you to make the right settings and measurements.
Productivity: An easy-to-understand oscilloscope makes it easier for new users to quickly familiarise themselves with the device and work productively.
Economic efficiency: Modern oscilloscopes offer a wide range of functions for sometimes complex measurement applications. A user-friendly design enables the user to understand these functions, use them effectively and fully utilise the performance of the device.
Ease of use: The arrangement of the operating elements and the design of the screen influence the comfort of operation, even over longer periods of time.

How do the sampling methods differ?

A distinction is made between a real-time oscilloscope and a sampling oscilloscope (equivalent time oscilloscope). With some oscilloscopes, the sampling method can also be selected. During sampling, part of the input signal is converted into electrical values. The value of the displayed sampling points corresponds to the amplitude of the input signal at the time of sampling. A digital oscilloscope displays a series of sampling points with the measured amplitude on the y-axis and the time on the x-axis. This reconstructs the input signal.

How does a real-time oscilloscope (real-time sampling) work?

A real-time oscilloscope can display the current values present at the A/D converter. Real-time sampling is ideal for signals whose frequency range is less than half the maximum sampling rate of the oscilloscope. The real-time oscilloscope can also be used to record one-off or sporadically occurring, transient signals. This requires a very high sampling rate. Real-time sampling generally requires a high memory depth to store the signals after digitisation.

What is a digital sampling oscilloscope?

In a digital sampling oscilloscope, the positions of the attenuator or amplifier and sampling bridge are reversed compared to the DSO/DPO architecture. The input signal is sampled before attenuation/amplification and converted to a lower frequency. This results in a very high bandwidth. The disadvantage is a limited dynamic range. In addition, no protective diodes can be used before the sampling bridge, as this would limit the bandwidth. This reduces the input voltage of a sampling oscilloscope to around 3 V compared to 500 V for other types of oscilloscopes.

What is a Sampler-extended Real-Time Oscilloscope (SXRTO)?

SXRTO oscilloscopes combine the advantages of real-time and equivalent time sampling. Its architecture utilises two independent cyclic processes: If a sampling sequence is triggered by a trigger event, the oscilloscope takes as many samples as possible. The oscilloscope measures the time interval between the trigger time and the first sampling time. All subsequent sampling times are determined by the internal sampling generator. If a trigger event is repeated, the sequence starts again. As the occurrence of the trigger event and the sampling generator are not time-correlated, a sampling sequence takes place at different times in relation to the trigger. By measuring the time intervals, the individual sampling values can be precisely assigned to each sampling sequence on the time axis. This type of signal sampling (= random sampling) leads to a very high sampling rate.

What is a PXI oscilloscope?

PXI (PCI eXtensions for Instrumentation) is an industry standard in measurement and automation technology. A PXI system consists of three hardware components: Chassis, controller and peripheral input/output modules for data acquisition, control, and regulation, including oscilloscopes. The oscilloscope modules can be integrated into the PXI platform and replace conventional desktop devices. PXI oscilloscopes are flexible, software-based measuring devices. They offer users a particularly powerful and scalable test system.