The Challenges of GFCI Measurements

Figure 1: An example
of a GFCI

The ubiquitous ground fault circuit interrupter (GFCI), a fast-acting circuit breaker, has saved countless individuals from serious injury or death when they've inadvertently entered the low-resistance ground path of an electrical device or outlet. It's important to measure precisely the amount of time that elapses from when the 60-Hz cycle is present to when the GFCI disables the ground path. Other tests include determining the start, stop, and duration of the GFCI's tripping time. Let's take a look at the challenges these measurements present.

Performance Considerations For Optical Modulation Analysis

Figure 1: Error-vector magnitude defined

In recent posts, we've covered the fundamentals of coherent signals and the basics of optical modulation analyzers. Let's now turn to the operational parameters of OMAs, in particular system bandwidth, and how that figure of merit in an OMA can determine how far your measurement system can take you in terms of meaningful analysis.

What Is An Optical Modulation Analyzer?

Figure 1: A representative block diagram of a coherent
transmitter and receiver

In an earlier post, we looked at some of the fundamentals of coherent signals: what comprises a coherent signal, how and why they're used, and a bit about how they're represented visually on an oscilloscope. The advent of coherent signals has brought about the rise of a new class of test instrumentation, known as an optical modulation analyzer (OMA). In this post, we'll examine what an OMA is and what it brings to the party above and beyond a stand-alone oscilloscope.