How zero blind time revolutionizes how you debug

What is blind time?

When you're using an oscilloscope, it's important to understand the two main phases of its acquisition cycle:

• sampling
• processing/display

During the sampling phase, the oscilloscope records signals and waveforms from your circuit or device. Then, the processing/display phase kicks in, and sampling is paused. This pause in sampling is the blind time, and it can be a real problem for engineers and scientists. Why? Because during this time, the oscilloscope isn't acquiring any new samples and any important events or signals will be lost. If your oscilloscope has a long blind time, you could end up missing out on critical information. For some oscilloscopes, blind time can make up over 99% of the total acquisition time - that’s a long time to be blind!

The blind time is dependent on two main things:

• The number of samples that must be stored and processed: the greater the number of samples, the longer the blind time.
• The amount and type of processing: different analysis functions and processing parameters have different processing requirements. For example, using a narrower resolution bandwidth with a fast Fourier transform will significantly increase blind time.

What is the oscilloscope update rate?

When it comes to oscilloscopes, one of the key factors you'll want to consider is the update rate - that is, how quickly the scope can trigger, process and display sequential waveforms. The higher the update rate, the better, as it means you'll be able to complete your tests more quickly and with greater confidence in your results.

The update rate is inversely proportional to the total acquisition time: the longer the total acquisition time (which includes both the sampling time and the processing/display time), the lower the update rate. As we've seen, blind time is a major factor in determining the total acquisition time. Therefore, the longer the blind time, the longer the total acquisition time and the lower the update rate. That's why it's so important to choose an oscilloscope with a short blind time. By minimizing the time during which the oscilloscope isn't acquiring new samples, you can shorten the total acquisition time and increase the update rate. This, in turn, will help you get more accurate and reliable test results and reduce the overall time it takes to complete your projects.

If you’re looking for an oscilloscope with an excellent update rate, be sure to the check out the R&S®MXO 4: it boasts the highest maximum real-time update rate in the world - acquiring, processing and displaying up to over 4,600,000 waveforms/s.

Minimizing blind time: Is zero blind time possible?

Unfortunately, no oscilloscope can have a blind time that is truly zero, but some modern scopes get very close, with blind times in the nanoseconds range. For instance, the R&S®MXO 4 offers a minimum blind time of less than 21 ns between consecutive acquisitions and the fastest update rate in the world. This impressive performance is largely due to its high-performance application-specific integrated circuit (ASIC). An ASIC provides faster, more efficient signal processing and is one of the primary ways in which a manufacturer can reduce the blind time of an oscilloscope. Older generations utilized general purpose hardware for signal processing and control. This limited oscilloscope capabilities, and high-speed data acquisition and real-time signal processing were impossible. An ASIC specifically designed for an oscilloscope can provide dedicated hardware for trigger processing or data acquisition, and it can perform these functions far more efficiently than a general-purpose processor, thus reducing blind time.

Certain oscilloscopes come with features that are designed to reduce blind time:

• Segmented memory: The oscilloscope only captures the parts of the signal that you are interested in and ignores the rest. This can greatly reduce the amount of data that the oscilloscope has to process.
• Interleaved sampling: The oscilloscope uses multiple ADCs (analog-to-digital converters) to sample the signal at slightly different times and then combines these samples to create a more complete picture of the signal.
• Parallel processing: The oscilloscope has multiple processing paths, allowing it to process one segment of data while capturing another.
• High sample rate: The oscilloscope can capture and process data more quickly.

You can also optimize oscilloscope settings to reduce blind time. For example, if you are only interested in a particular part of your signal, you can adjust the settings to focus on that part. This includes adjusting the timebase settings and the trigger settings to focus on the relevant part of the signal.

How a short blind time benefits debugging

Imagine a world where you could catch every glitch, voltage spike or high-frequency signal with ease. Sounds too good to be true, right? Well, it's not. With a near-zero blind time, modern oscilloscopes such as the R&S®MXO 4 can make this dream a reality.

In the world of debugging, short blind time is an absolute game-changer. It minimizes your chances of missing rare, transient events like glitches or voltage spikes. This is especially important in applications like power electronics that involve high-frequency switching signals.

A short blind time also simplifies the analysis of complex signals. With a higher update rate, more observed waveforms can be captured in a single observation window, allowing for a more accurate and detailed representation of the signal. Take a look at the image below. The waveform captured with a faster update rate is both more precise and detailed than the one captured with a slower update rate. This is particularly useful for noise or small, infrequent events that could easily be missed with a slower update rate. A higher update rate also allows you to trigger on these events. This can be critical for many different applications such as digital communications, where signal quality is key to performance.

Other benefits of shorter blind time

A short blind time reduces test time not only by assisting with debugging but also by enhancing usability and instrument responsiveness. Most modern oscilloscopes prioritize waveform processing over user interface. In practice, this means that a scope only updates its display and responds to user input at the end of its blind time. Therefore, a low blind time makes a scope more responsive both in terms of display and control. This naturally decreases frustration and the probability of user error.

Higher statistical confidence is another benefit of shorter blind time. Oscilloscopes are often employed to generate statistical data, and each acquisition is treated as a sample of the input signal. The more samples there are, the smaller the confidence interval becomes, allowing you to be more confident that the measured statistics are close to the actual values.