An interview with Scott Leithem
In today’s fast-paced and technologically advanced world, precision and accuracy in measurements are more critical than ever. Whether it’s in aerospace defense, public safety, automotive, or commercial wireless markets, the smallest measurement uncertainties can lead to significant consequences. To shed light on this crucial topic, I sat down with Scott Leithem, a lead engineer at Keysight, to discuss the importance of Keysight-certified calibration services in reducing measurement risk. Scott shares his insights and real-world examples that highlight why calibration is a vital component in ensuring the reliability and performance of high-precision instruments.
Sandra: Hi Scott, thank you for joining us today. Can you start by telling us a bit about your role at Keysight and why calibration is so important in your field?
Scott: Absolutely, Sandra. I am currently an engineer in the planning organization of Keysight Global Services, where I develop services that help our customers achieve their desired outcomes — quicker. As an electrical engineer focused on calibration in aerospace defense application engineering, I often discuss with customers the critical aspects of measurement uncertainty, traceability, and the importance of calibration. Thorough test equipment calibration is often an overlooked lynchpin that can mean the difference between success and financial loss, reputation damage, and even life-threatening situations.
1 dB uncertainty can cost a satellite provider millions of dollars
Sandra: That sounds crucial. Can you give us some real-world examples where measurement uncertainty has had significant impacts?
Scott: Certainly. Consider that a poorly calibrated power sensor can easily contribute 1 dB measurement uncertainty. The problem is that there are already narrow margins such as 3dB designed in for atmospheric effects like rain fade. So, 1 dB of added uncertainty can therefore mean the difference between receiving the signal or not during a storm. Putting this into business impact, consider an example of a 30-second commercial aired during prime time hours which costs on average 350K $s. This money is wasted when a storm causes a loss of reception. In addition, repeated losses of reception frustrate satellite TV subscribers causing them to switch providers or re-think their subscriptions completely.
1-degree angle error can result in a fighter jet being 5.2 miles off target
Sandra: Wow, that’s quite impactful. What about in the context of defense applications?
Scott: Consider a fighter jet flying along the coast at approximately 300 miles from shore. It is seeking to identify a target for reconnaissance purposes from among several other targets emitting wireless signals. For the fight jet’s radar to identify the target of interest, precise knowledge of both direction and range is required. Measurement uncertainty or error due to out-of-tolerance instruments presents a significant risk in this scenario. For example, an out-of-tolerance cal kit can introduce significant systematic error, and in this case, only a 1-degree error at this range results in the radar reading 5.2 miles off target.
2 dB uncertainty can result in a 32.6-mile reduction in range
Sandra: As you mention range, could there even be a scenario where the radar cannot see any of the targets anymore?
Scott: Yes indeed. The maximum range in a radar receiver can be limited by uncertainty due to a bad calibration. In this case, noise in the environment from other targets can reduce the range of the receiver. If the receiver is designed with a specific margin for noise, any added uncertainty reduces that range. For example, a 2dB uncertainty in sensitivity at a 300-mile range can result in a 32.6-mile reduction in range. The radar then cannot see any of the targets anymore.
3 dB uncertainty can result in a 50% loss of range
Sandra: That’s quite a margin of error. How does this translate to public safety and public radio usage?
Scott: Public radio usage covers multiple applications such as medical, public safety, or military. Field radios can be lifelines for first responders, in events such as natural disasters like wildfires, hurricanes, or flooding. First responders and team members expect a certain range between the mission, and the mission control distance and expect the radio to perform over that distance. Unfortunately, if max power output is 3 dB lower than expected, then there can be a loss of range of 50%—which translates to no communication over the full distance.
1dB added noise can result in failed transmission at a critical moment
Sandra: What about commercial wireless applications? Do regular cell phone users like you and me feel the impact of a lack of periodic calibration of test instruments?
Scott: Yes. A successful wireless link depends upon many factors, but in most cases, most would agree that 1 dB of added noise at current cellular frequencies does not noticeably affect the quality of service. On the other hand, the commercial wireless market is changing rapidly to satisfy the demands of consumers, such as 100x faster data rates, the ability to handle much higher capacity, and the expectation that service quality will remain the same even in a dense environment such as a busy sports stadium.
One of the biggest challenges is therefore the additional noise that wider bandwidth signals inherently have and the dramatically increased propagation losses at mmWave. Let’s say you and I are part of the crowd in the aforementioned busy sports stadium where you may have 100’s or 1,000’s of people simultaneously using their phones to watch or upload videos, photos, etc. Due to the added noise and reduced sensitivity in these conditions, a 1 dB shift in the instrument noise floor can make the difference between a working link and a live video that drops out during a critical moment of the game. This is because the margins have been significantly reduced at these frequencies and bandwidths, meaning very little leeway for shifts in or drifting test instrument performance.
0.1-microsecond delay can result in a 30-meter error at a 100-meter range
Sandra: The last industry we want to touch on is automotive. What I have learned so far makes me strongly believe that calibration has an impact on safety. What can you tell us about that?
Scott: There is no room for error when it comes to automotive safety, as demonstrated by the very small design margins that we normally see in the industry. This includes compromised margins resulting from a poor calibration. For example, a 0.1-microsecond uncertainty in time delay created by a radar target simulator due to drift and/or a poor calibration, can result in a 30-meter error at a 100-meter range – a significant error in distance that can have serious safety implications.
Sandra: It sounds like calibration is essential across various fields. Can you explain what a Keysight-certified calibration entails?
Scott: A Keysight-certified calibration ensures that measurements are accurate and traceable. Unfortunately, some calibration providers cut corners, skipping critical tests related to accuracy and noise floor. At Keysight, we emphasize the importance of regular, thorough calibrations with state-of-the-art electronic test equipment to maintain the performance of high-precision instruments.
Sandra: Thank you for those insights.
I invite everyone to check out the many resources we have on calibration, including understanding measurement risk and traceability, how to know if your calibration is effective, and more by visiting our calibration services page. And I encourage you to check out KeysightCare to make sure your instruments are regularly scheduled for the most thorough calibration that is the best fit for your application, to ensure your high-precision instruments continue to work like-new, every time. KeysightCare Enhanced includes a calibration service of choice based on the equipment’s recommended calibration interval. KeysightCare Enhanced offers full protection for your innovation investment including prioritized technical support, repair, and calibration coverage. Are you ready to discuss your calibration options?
About Scott Leithem:
Scott is an application engineer focused on planning and designing services for Keysight solutions, with an additional focus on aerospace and defense applications. He has been working for Keysight for 12 years, where he has spent the last 8 years focused on calibration, understanding and calculating measurement uncertainties, and ensuring the accuracy of measurements. Before that, Scott worked as a support engineer and product manager, specializing in signal sources and signal analyzers. He has a Master of Science in electrical engineering from the University of Illinois.