Past Columns

Whenever an electronic circuit is first energized, transients occur in current and voltage waveforms. These start-up transients can affect the electrical and thermal behavior of components and circuits with serious reliability, EMI, and random effects. Try to characterize how your circuits start and stop.

There always seem to be questions about hi-pot testing. Maybe I can present some of those questions and their answers.

Common mode currents are in the origin of many typical problems in EMI/EMC and RF electronics. The best way to understand those currents is to visualize them in your scope or spectrum analyzer.

How does safety work? That is, given a hazardous situation, how do we prevent injury from that situation?

If you are evaluating a design (i.e. power supply) from the EMI/EMC point of view, avoid replacing the real load with some kind of “equivalent resistor.” Differences can be really impressive.

Parasitic oscillations are one of the four typical causes for emissions in EMI/EMC problems. Try to reduce the gain or break the feedback and the problem could be solved at low cost.

Did you ever wonder why we use 0.1 ohm (and sometimes 0.5 ohm) for the ground impedance value for plug-and-socket connected equipment?

The “power distribution system” is all parts of an electric system between the “bulk power source” and the consumer’s service-entrance equipment.

After causing a bit of a stir in the compliance testing industry in the last few years, the FCC recently defused some tension when they accepted a pair of US-based Accreditation Bodies to accredit laboratories in foreign lands.

Many EMI and SI problems are related with a combination of inductance and capacitance without losses.