Is it plausible? Does your idea violate any known physical laws? Are you asking for a new light bulb that has 110% efficiency? If it passes the plausible test, we go to the next phase:

Is it feasible? Can your product be made, given a reasonable budget in a reasonable time frame? Often the ‘existence proof’ of a similar technology or device can help us answer this with minimal effort. Or we build a prototype to test the most tricky aspect – this becomes an object that can be tested, used, and evaluated, which brings us to the third phase:

Here it is. It’s tangible. A prototype, a ‘proof of principle’, a first example that shows what kind of performance and cost can be expected. Something you can use. This is a way to find the ‘slap on the forehead’ mistakes, and find them early in the project. Before you waste a lot of time, effort money on tooling, marketing, etc.

In the next weeks I’ll be writing about more specific examples of this process flow.

Bec is helping us make this motion stage, based on a salvaged DVD player, a platform for some new precision products. With an encoder capable of 15um resolution from Austria Micro, and controls theory support from Bec, we look forward to using this prototype in our shop to improve our optical measurements.

A few prototype motion stages getting outfit with precision encoders.

Nixie tube tester by David A. O' Brien

Recently we started working with David O’ Brien, whose list of accomplishments is too long for this single posting. One of his many devices is this great nixie tube tester – runs on a single 9V battery. You can see more of his fabulous work here: David O’ Brien’s website

Here’s the story: Designing and debugging a high precision A/D stage, you will want to know how quiet the voltage reference really is. When I worked on a 20 bit A/D board, I found this amp a great way to prove that a simple voltage regulator was not good enough as a reference voltage (measured data trumps an any preconceived notions). It was a big help getting the shielding and grounding debugged too!

Here's the amp on the bench, next to a 9V battery. Click on image to enlarge it.

A view inside the prototype x1000 low noise amp. Click on image to enlarge it.

Since most ‘scopes have about 5mV/Div at their highest gain, this AC-coupled amp allows you to ‘see’ to 5uV/Division. For a 5V full scale A/D that’s 1ppm per division on your ‘scope. Trust me, you’ll see things there.  (I read that Pasteur freaked out his dinner hosts, using his microscope to look for germs on his food. He was ‘debugging’ in his day too, with his new favorite toy).

Here’s a pdf of the schematic – it’s based upon the design in the book Low-Noise Electronic System Design, by Motchenbacher and Connelly (a highly recommended text). Since the text came without the amp, I had to make one myself.

SCHEMATIC-low-noise-x1000-amp-MODEL-101

I also have a SPICE model for it, using Linear Tech’s LT-SPICE and I’ll send it to you, if ask.

Based upon Motchenbacher and Connelly’s excellent book ‘Low Noise Electronic System Design‘. Click on the link for the pdf or on the image for a JPEG version.

pdf: Build-your-own-wideband-attenuator

Build your own wide bandwidth frequency compensated attenuator to test amplifiers.

Ok, stand in front of the mirror and it swaps left and right – you wiggle your right hand, the left hand wiggles in the mirror. But, up and down don’t get swapped, the top of your head is still at the top. More puzzling – when you lie down, the mirror still ‘knows’ when you right hand moves, and ‘shows you’ a left hand moving. Asking a few good questions leads to the real answer. Here’s another Feynman video. Enjoy.

No, it’s not those flanges (though that seems obvious at first). In a way it’s a kind of ‘closed loop servo system’ or a self-correcting mechanism. In mechanical design I’ve heard this idea called ‘self-help’ where loads get distributed evenly by a careful design (see the book The Elements of Mechanical Design by James Skakoon for more on this topic).

This shows a microcosm of the job we do working with clients, solving problems – we always care about how things really work, and this video shows an example where the first ‘obvious’ idea may not be quite right.

In any case, it’s always fun to hear Feynman explain stuff. There’s a load of footage of him at youtube, explaining fire, light, uncertainty. Enjoy.

This shows the improvement in clock accuracy at NIST from 1950 to 2000.

Given how accurately time is measured, we wondered ‘how is the kilogram calibrated?’

We learned that, according to NIST,

“The magnitude of many of the units comprising the SI system of measurement, including most of those used in the measurement of electricity and light, are highly dependent upon the stability of a 131-year-old, golf ball-size cylinder of metal stored in a vault in France”.

And over the years the International Prototype Kilogram, the IPK, and its copies that are distributed around the globe, have ‘gained weight’. There’s more here at wiki:  http://en.wikipedia.org/wiki/Kilogram

Here’s the graph to show it:

Weight change of the standard kilogram and its copies over 100 years.

NIST further explains:

“Mass drift over time of national prototypes K21–K40, plus two of the IPK’s sister copies: K32 and K8(41).^{[Note 9]} All mass changes are relative to the IPK. The initial 1889 starting-value offsets relative to the IPK have been nulled.^[12] The above are all relative measurements; no historical mass-measurement data is available to determine which of the prototypes has been most stable relative to an invariant of nature. There is the distinct possibility that all the prototypes gained mass over 100 years and that K21, K35, K40, and the IPK simply gained less than the others”.

Uncertainty,  it seems, is here to stay.

However, there’s an improved kilogram standard being worked on, called the Watt Balance, which measures the electrical power used to null the weight of a one kilogram test specimen. To get accurate results, NIST must establish the gravitational force accurately. Here’s a link to a NIST article describing how they do it:

http://nvl.nist.gov/pub/nistpubs/jres/106/4/j64schw.pdf

Which reminds me of a Jim Williams article from Linear Tech, where he describes a VERY accurate electronic weigh scale, capable of measuring your heartbeat – since all the blood pumping and flowing changes your weight, a little bit. He called it a ‘ballisto-cardiogram’. Here’s where you can read more, in AN43 that Jim wrote for Linear Tech, about bridge circuits – including how to make a scale that can resolve 0.01 pound at 300 pounds full scale, or about 33 parts per million. It uses a clever circuit to achieve balance quickly and accurately, check it out:

http://ece.olin.edu/instrument/LinearAN43.pdf

Most lenses are spherical, in that each curved surface is some part of a sphere (usually a big radius compared to the lens glass diameter). Lately we’ve been working on some systems that require the use of lenses that have an ‘aspheric’ curve. These are more unusual, but if you can solve a problem that is otherwise unsolvable, ‘unusual’ is a good answer. Ok, maybe since I’m the electronics guy, I’m impressed with the precision of these optics and their measurement – I think you’ll be too, when you look into it.

We’ve found some references about designing and testing these asphere elements. Start with the article by Jay Kumler, and  then read the other two about some fancy gear to test these aspheres.

Jay Kumler, Designing and Specifying Aspheres for Manufacturability, by Jay Kumler of Jenoptik-Inc

Interferometric Measurement of Rotationally Symmetric Aspheric Surfaces, by Michael Kuechel of Zygo

Subaperture stitching interferometry of high-departure aspheres by incorporating configurable null optics, by Andrew Kulawiec, Markus Bauer, Gary DeVries, Jon Fleig, Greg Forbes,
Dragisha Miladinovic, Paul Murphy of QED Technologies.