The FFT can measure phase angle, but what appears to be a meaningful result might just be the arctangent of a ratio of rounding errors. Throughout this series, we reviewed the fast Fourier transform (FFT) as implemented in Microsoft Excel and investigated windowing functions. In this final part, we’ll cover phase measurements, but first, let’s […]
FAQ
How to separate differential and common-mode harmonic noise currents
Differential-mode and common-mode currents can cause your product to produce radiated and conducted emissions. These three techniques can help you measure them.
Why does the Fourier transform provide apparently inaccurate results, and what can I do about it? part 2
A bare-bones implementation of the Fast Fourier Transform helps illuminate how to extract frequency information from input data samples. In part 1 of this series, we reviewed the discrete Fourier transform (DFT) and manually calculated one DFT shown in Table 1. Table 1. Manual DFT results DFT input Complex DFT |DFT| 3 12 + j0 […]
Review: Electronic bug and hidden camera detectors
Do you want assurance that cameras embedded in everyday devices don’t spy on you? Then you should check for cameras, SD card slots, and Wi-Fi-connections. We reviewed two devices that help you find those lurking spies. While discovering a hidden camera in an Airbnb, VRBO, or hotel is rare, there have been reports of travelers […]
Why does the Fourier Transform provide apparently inaccurate results, and what can I do about it? part 1
This multipart series will review the discrete Fourier Transform and describe how to avoid common problems when transitioning from the time to frequency domain. A recent post on phase noise discussed expressing a function of time as a function of frequency. The Fourier Transform is the well-known road from the time domain to the frequency […]
How to use remote sensing for DC programmable power supplies
In this FAQ, you’ll learn how to know if your test application needs sensing and how to properly wire a power supply to a load. Calibrating certain sensing circuits, such as those used in electric vehicles (EVs), is critical to get right. An inaccurate calibration of an automotive battery monitoring circuit could, for example, allow […]
What is phase noise, and how can I measure it? part 1
Phase noise is an artifact of a nonideal oscillator and is best investigated in the frequency domain. Phase noise accompanies the generation of any real-world sinusoidal signal. You can think of it as the analog equivalent of digital jitter, which we covered in an earlier series (read part 1 and part 2). Recall that jitter […]
How to test the automotive SENT protocol
Oscilloscopes and dedicated software can help analyze SENT data. In “What is the automotive SENT protocol?” we looked at the Single Edge Nibble Transmission (SENT) protocol, as defined in accordance with the Society of Automotive Engineers (SAE) J2716 standard. We reviewed the SENT message frame, which includes a synchronization/calibration pulse followed by a status nibble, […]
What’s the difference between a USB oscilloscope, spectrum analyzer, and digitizer?
USB oscilloscopes are highly versatile instruments. With the right software, they can perform functions usually reserved for spectrum analyzers and digitizers. In some cases, however, special instruments are needed for optimal results. This FAQ compares the functions of oscilloscopes, spectrum analyzers, and digitizers with USB interfaces. They are called USB devices because they connect to […]
How to use simple antennas for EMI troubleshooting
For general troubleshooting, you can use consumer-grade antennas such as for TV. Pre-compliance tests require calibrated antennas. Antennas are important for capturing radiated harmonic emissions from electronic products. You can use them for simple troubleshooting or for calibrated pre-compliance testing. For troubleshooting purposes, you can use almost any uncalibrated antenna. I’ve even seen engineers use […]