Re: ADC mux charge injection on commercial DAQ boards

It's a real talent to be able to reduce a problem to its basic, simplistic core. In digital design, that means recognizing the minimum number of stages and states necessary; in analog design, it's fuzzier but still real. I've seen serious industrial and aerospace electronics that was 5x or even 10x more complex than necessary. We recently replaced a GEC heads-up display driver, for the AC130, with less than a tenth of the original hardware, which incidentally had an MTBF of 22 hours.

Sometimes people get mad, or refuse to believe, when you show them a simple solution.

John

Or even one that's too cheap. Figure that out. Those are two classical forms of 'thinking inside the box'.

Cheers,

Phil Hobbs

Some peoples' egos are stroked by buying expensive parts!

Of course, you can overdo (underdo?) it, especially in analog design. Say, when two resistors control three important parameters, and you're boxed into a bad solution.

John

Nah, then you just redesign it so that Herr Ohm or Mr. Faraday or Drs Eber and Moll look after the third parameter for you. ;)

I'm not really advocating going back to 5-tube radios, but I've been scarred by my Footprints experience...it's really really hard to get people to let you save them money sometimes--even big money.

Cheers,

Phil Hobbs

:-(

...Jim Thompson

I designed a TTL-based PWM DAC once, that looked fine on paper. It had two trimpots, to set gain and offset. Once we built a bunch, we found that *nobody*, YHS included, could set the pots. The interaction was so bad that the adjustments would rapidly diverge. We had to work out a written algorithm that had to be rigorously followed. After a modest redesign, the next rev had nearly orthogonal adjustments.

John

You can expect people to be wary as the result of experience. While more expensive doesn't necessarily mean better. Cheap often means poorly built. If the difference from previous expectations is large the obvious question is what has been left out/missed?

Of course when the design truly is that much better and cheaper it can face a bit of a credibilty hurdle.

Robert

Been there. I had a *beautiful* measuring interferometer with badly interacting controls like that--it worked great but I had to rip the covers off it every time I wanted to use it, so I could put a white card in the beam inside the box.

My usual rule of thumb is that 1/10 turn nonorthogonality per turn of the other control is OK, 3/10 requires an expert, and any more than that is next to impossible. (And this applies in both directions, so putting one adjustment on a fine thread doesn't help.)

Cheers,

Phil Hobbs

Understood. What actually happened to me was that I had this 96-pixel thermal IR camera with very competitive sensitivity (0.13 K NETD), that cost roughly $50 in parts in single quantity--mostly for a well-upholstered PIC, some flash memory, and Maxim RS-232 ICs, because it was a development version designed by a physicist. A very mildly reengineered version would have been $50 total in quantity, and the sensor part itself was less than $10.

The nearest equivalent used a germanium lens and a PZT pyroelectric array, and cost $4000 for poorer performance, albeit with 256 pixels.

In licensing conversations, we asked for $25 per sensor in royalties. You'd think that the business folks would be thinking, "Hmm. So my cost would go down from $4k * 2000 sensors per year to $75 * 2000 sensors per year, which is $150k vs $8M. I can move to Aruba!"

What we actually got was "That's a *FIFTY PERCENT ROYALTY!* Are you NUTS?"

Wasn't just once, either. It would have been a much more attractive deal to them if it had cost $1000 per sensor and not $50--but we couldn't figure out how to make it that expensive.

Cheers,

Phil Hobbs

Le Wed, 03 Oct 2007 02:44:53 -0400, Phil Hobbs a écrit:

Then propose to build it yourself and sell it for $1000. When they say "hey, but it costs next to nothing to you", propose to settle to a $250 royalties and underline that it's a huge 75% saving for them :-)

Deja vu. I designed a series of electrical measurement/datalogger boxes, for utility end-use surveys (which was a big business once) and licensed it to an outfit in New Orleans. They sold for 20x what they cost to make, and they made tons of bucks, but my 15% royalty still grated on them. So instead of working on new products with me, they hired an attorney who hired a California design team to do a legally defensable "clean room" redesign of the same functionality. They spent over a megabuck and never finished the project, the end-use market dried up, they had no other products in the pipeline, and the company died. All so they could show an "arrogant smart-allec Californian" that they were just as smart as him.

Secrecy, jealousy, NIH, and narrowband greed kill more companies than trade secret theft or honest competition. Smart people make alliances so everybody can do what they do best.

Hey, the world still needs an affordable thermal imager. We have a Flir and it's hard to believe we ever survived without it. But it cost $10K. If they cost $250 or so, you could sell them at Home Depot.

John