Technical Insights

A powerful and versatile eight-in-one test bench in one box

2020-05-11  |  9 min read 

“If you were the last engineer on earth, what would be your set of “root” test equipment so that you could rebuild everything else?”

 

I was recently in a meeting where an executive posed that thought-provoking question regarding our portfolio of test equipment. Reflecting on it later, I came up with my list:

I need to generate signals that simulate useful conditions. I need to see signals in time and frequency domains. I need to work with digital logic and recreate histories. Finally, I need to measure voltages and current and count instances. Whoa – that’s a lot of roots! Not to mention a lot of clutter on my bench. Wouldn’t it be better to have it all in just one box? Thankfully, I’m not the last engineer on earth, and a one-box solution exists today to meet all my needs in a remarkably powerful combination.

Everything that you need, and nothing that you don’t

We bench test engineers have a challenging job to do, and a finite amount of time to get it done. Couple that with an environment where limited prototype assets are faced with limited availability of test equipment. I appreciate the benefits of one-box solutions, whether implemented in hardware, software, or a mixture of both. But they always involve compromises in capacity or performance. Those compromises shouldn’t be blind. From a deep, hands-on understanding of bench test customers’ needs, the best one-box solution has been brought to life, enabled by state-of-the-art processing power.

Let’s run down that “last engineer on earth” list.

  • Signal generation is accomplished with a function generator, better yet an arbitrary waveform generator. It’s got to hit 50 MHz and be flexible.
  • To see signals in the time domain, an oscilloscope is required. To meet today’s needs it must have 8 analog channels. And forget about anything less than a 6 GHz bandwidth – it’s not the stone age.
  • To see signals in the frequency domain, a spectrum analyzer is needed. But don’t make it simple-minded – I need real-time spectral analysis (RTSA) to catch real-world problems. A 50 MHz frequency response analyzer completes the picture.
  • Digital logic and histories need a fast 16 channel logic analyzer and a protocol analyzer with dozens of useful protocols available.
  • To count instances and measure voltages and currents I need a 10-digit counter and a four-digit DVM.

Bench test engineers need their function generator, oscilloscope, spectrum analyzer, frequency response analyzer, logic analyzer, protocol analyzer, counter, and DVM at different times and for different test needs. But eventually, they need them all.

Real-world use case: Glitches happen

Let’s illustrate the importance of a powerful eight in one instrument with a real-world use case. A new Wi-Fi 6 consumer product design has an intermittent problem. It’s almost ready for manufacture, but in some of the QA and manufacturing tests, the device has exhibited a “glitch” that resets it for no reason. In this use case, two built-in instruments come to the forefront – a “fault hunter” enabled 6 GHz oscilloscope and an RTSA enabled spectrum analyzer.

Irregular or spurious signals are the hardest to find because it is difficult to know when it will occur next so that its cause can be isolated. Design engineers, test engineers, and most of all, customers hate to hear “fault not replicated”. You need an instrument to cut through the mystery and resolve the problem quickly.

Smart "fault hunter" function: The best path to capture glitches is with oscilloscope software that learns what “normal” signals are for a device under test and then automatically compares the normal signals to anything that is abnormal. When the abnormal signal occurs, the scope captures everything that went on at the same time and stores it in memory. To be effective, the memory must be both segmented and deep. A device under test exhibiting this type of behavior can be set up to run over a weekend so that when the test engineer returns on Monday they find exactly when the glitch occurred, what it looked like, and eight full speed analog as well as 16 digital channels of what else was happening in the system that may have caused the glitch.

Knowing the glitch’s “snapshot”, the test engineer can more precisely probe the most likely root causes of the problem. In our use case, the issue has occurred several times over the weekend on the falling edge of the switching power supply’s cycle. That’s when the test engineer knows to shift from the time domain to the frequency domain and pulls up their built-in spectrum analyzer.

RTSA enabled spectrum analyzer: An important difference exists between simple spectral analysis based on individual Fast Fourier Transforms (FFT) with lots of dead time between acquisitions, and real-time spectral analysis that uses multiple FFTs. Real-time spectral analysis applies many thousands of overlapping samples for each sweep, achieving a 100% probability of intercept for intermittent power supply noise and noise effects, signal crosstalk, and the influences of the environment on the signal.

Continuing our use case, the test engineer sets up their probes on the device under test switching power supply input and output, the device under test CPU, and the power supply connections to each board. A frequency transient shows up at the power supply output and simultaneously at the antenna board’s input. Adjusting the current that is supplied to the antenna board upward, the transient disappears. The root cause is found, and the easy solution gets the Wi-Fi 6 product back on its delivery schedule.

Without the powerful combination of the smart "fault hunter" enabled oscilloscope and the RTSA enabled spectrum analyzer, finding this problem could have been hit or miss for weeks on end. Of course, a separate real-time spectrum analyzer box would have done part of the job, but that would add both cost and clutter to the bench. Separate boxes for all the needed bench instruments would introduce their own issues of noise and crosstalk.

Get from symptom to root cause to solution faster with eight instruments in one

The last engineer on earth doesn’t have time to waste when there is a whole industry to rebuild. Real-world test engineers don’t have time to waste either. We need the right equipment at our fingertips to get our job done. It’s not that unique to have many instruments built into one box. What is unique is the power of each to get our challenging work done right.

For your design to shine, your test equipment and associated software applications must be highly capable and tuned in to what every bench test engineer needs to solve problems. Why settle for anything less? To find out more about Keysight’s powerful new eight instruments in one, Infiniium MXR visit: Infiniium MXR-Series Real-Time Oscilloscope.