Though some technologies seem to change every day, some live on for years and with good reason: New means unproven.
In an EDN post titled When wires become components, you can see the care that goes into making calibration-grade resistors and inductors. Today, we'll get a look at test equipment that remains in products after many years.
At IET Labs, as at most companies in the calibration and metrology business, you won't find the latest, coolest electronic equipment. You will find equipment that has been manufactured the same way for decades. That because new isn't always better. Calibration people are a skeptical group for whom "new" equates to "unproven." A proven history of measurement quality overshadows the latest digital technology.
In addition to seeing many decade boxes, I saw a megohmmeter that's still made with a vacuum tube (see the first video after the sideshow), reference capacitors used as capacitance transfer standards, and reference inductors. The second video below shows how to perform a comparison of a reference inductor to an unknown inductor.
The last few slides in our slideshow tour of IET Labs were taken in the front lobby. There are all kinds of equipment there, some dating back to before you were born.
Click the image below to open our slideshow.
A megohmmeter manufactured by IET labs still uses a vacuum tube. "We'll manufacture these meters for as long as we can get the tubes," said electrical engineer Joel Goldberg.
There's a few Russian companies that manufacture vacuum tubes, some even make them to order. A friend of mine wanted to make a valve amplifier that actually produced high quality audio and designed a valve that met hit criteria. He's using one of these companies to make it :-)
The caption says there's a CRT in the upper right corner of the capacitance bridge panel in image 13, but is it really? I have a hunch it's just a little screen over the top of a 6E5 "magic eye" tube but I could be wrong, those were quite common on test equipment of that vintage and function. Basically it's a replacement for a meter when all you needed was an indication of an analog null condition, like showing that the bridge was properly in balance.
I worked on a lot of old equipment, and it all had the same problem, it was unreliable, drifted like crazy and NEDED calibration to attain what are now considered mediocre specs. These days any voltmeter from a company like Fluke etc. that is ~1% accurate usually doesn't need calibration, we just do it because the standards say so. Get to 0.1% and you occassionally need calibration. Things sure have improved