Modular measurement technologies have made great strides over the last several decades. Commercial, industrial, and military users of test equipment now enjoy an unprecedented selection of test instruments in modular form, from audio through microwave frequencies. The excellent track record of the VXI modular format, with its 25-year history, has shown that it is reliable even across the environmental extremes faced by many military users.

In addition, the performance levels achieved in some recent products introduced in the AXIe and PXIe modular instrument formats show that these mechanical structures and electronic bus configurations sacrifice nothing in terms of performance compared to older test instrument set-ups. Still, adoption of test equipment that slides into a standardized module-holding chassis can be as much of a philosophical as a technological decision.

A tall enclosure full of 19-in. rack-mount test instruments is a familiar sight at most RF/microwave engineering facilities. Especially among “old-guard” engineers (this writer among them), working with such full-sized instruments—whether for prototyping or production—has earned a certain level of trust in these tools among many users. In fact, engineers old enough to remember the stacks of test equipment from Wiltron Co. or Hewlett-Packard Co. might also remember when the VXI modular format was first introduced … and the skepticism throughout the high-frequency industry that such “toy-like” products could ever perform at the level of those trusted rack-mount instruments.

To this day, many engineers still feel that way, even though the growing number of modular instrument products (and even modular instrument formats) is making it difficult to ignore the measurement possibilities offered by modular instruments. In terms of a philosophical choice, older engineers tend to more than lean towards using rack-mount test instruments. While they might eye the specifications for the latest analyzer or arbitrary waveform generator (AWG) introduced in one of the modular instrument formats, the equipment that they depend upon for their own measurements is all contained within 19-in. enclosures.

Adoption of critical test functions in modular form requires a willingness to abandon a long-trusted approach and to start with a new outlook on how measurements can be performed. A modular format offers many benefits, with the small size and conservation of power compared to full-sized instruments quite appealing to any electronic-facility manager.

To the working engineer, the flexibility to add or subtract test functions, such as a signal source or a digitizer, as needed (when the acquisition fits within the facility’s business plans, of course) represents a huge extension of engineering capabilities for any project. The fact that the functionality of a modular test system can be easily modified within one or two modular instrument chassis that can be moved around an engineering facility (unlike a 19-in. rack), and quickly reprogrammed by means of a commercial measurement software (such as LabVIEW from National Instruments), makes modular measurement solutions quite attractive to many users. 

For the most part, these modular test-equipment users are part of the next generation of engineers: younger users willing to try a new format because they did not grow up with the rack-and-stack instruments of their predecessors. They are open to a different test philosophy, one that will likely lead to the increased use of modular test instruments in the years to come.

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