imperfect exponential

I was considering a variable bandpass filter as a super low jitter cleanup filter after a DDS synthesizer, using the digital silicon capacitor things. But we decided to use an RF synthesizer chip instead of DDS. That's a whole nother story.

Hey, I'm an engineer. I never got good grades in Penmanship. Terrible, in fact.

Anybody who can see the scope timebase, and even think this could be

Chemistry is mostly about electrons.

Cheers

But where is the sportsmanship in this? That's almost like using a cake mix instead of making everything from scratch.

Some are. One guy I knew quite well started his company in the 60's. Up into his 80's he was always full of spunk and lots of ideas. Kept his company on a even keel and profitable for all those decades, was happily marrried for all those decades. Then pancreatic cancer took him :-(

I use Jiffy for my cornbread, and Bisquick for my pancakes, and Pillsbury roll-out dough for my pies. We have to keep moving up the abstraction stack.

The Safeway Select frozen Belgian waffles are actually pretty good.

Got to confess that we use pre-baked rolls and bread on the barbie. It needs about 10mins or 2.5mins per position on the grill. However, that is as far as we are willing to go up the abstraction stack. In other disciplines we are moving down the abstraction stack. Such as with beer where I now brew our own. The rewards are huge. Even a lot of high-Dollar store-bought beer now tastes bland in comparison.

You know the dramatically-poor capacitance vs voltage

I changed to a lower value and higher Z after I took that picture. ;)

Not that good, actually--apparently he abandoned his colleagues, his investors, his lovely wife and their many children (high school down to about kindergarten), and took up with a 22-year-old in another country. They'd probably have gotten over it a lot sooner if it had been cancer.

Some folks spread a lot of wreckage around.

Cheers

Phil Hobbs

We were going to put it on the cold plate of a thermoacoustic fridge--diode lasers don't like high temperatures one bit.

Yup. Neither are their lawyers. ;)

Cheers

Phil Hobbs

We had one case like that in town. His new wife is about the age of one of their daughters. It wasn't even any kind of meltdown that triggered it all. Those people can become very lonely once they become old and they and their new relations find out that their are ... really old and not so attractive anymore. A 40-year old woman in the prime of her life isn't usually very keen on having to care for an ailing septuagenarian husband.

Well, yeah, don't ever ignore physics.

More important, to characterize a capacitor linearity, use a reference and a device-under-test capacitor in series, driven through a floating transformer winding. Ground the center capacitor node, and either X-versus-Y the two probe-able voltages, or display the difference (X+Y) versus time, and twiddle the gain controls to undo the tilt.

Not only can an analog scope do this well, but it is likely to have superior resolution on that sum (of one negative and one positive signal). Vertical and timebase errors do not confuse such a display, though you DO rely on gain calibrations if you want to read off the capacitance ratio and get an absolute C value.

Galvanometers would be even better.

Hey, don't knock galvos. I have a laser beam position measuring gizmo that I built in 1990, according to the date on the case. It uses a germanium quad cell run in solar-cell mode (more or less open circuit)

D1 | D2

--------- Y D3 | D4

where D1-4 produce OC voltages V1-V4 respectively.

A dual op amp forms V2 - V3 and V4 - V1. Two zero-centre, edge-reading microammeters are mounted so that the needles move in X and Y. Resistors from the op amp outputs drive the meters with

VX = (V2-V3) + (V4-V3) = (V2+V4) - (V1+V3) and VY = (V2-V3) - (V4-V3) = (V2+V1) - (V4+V3) .

The quad cell is fitted on the axis of a 30-mm aluminum cylinder that fits standard 30-mm cage-type optical mounts.

It's a super quick solution to beam alignment from 350-1800 nm.

Unfortunately you can't get the meters anymore, or I'd build another one.

Cheers

Phil Hobbs

Should have added: because the diodes are pretty nearly logarithmic, the beam position signal is more or less independent of beam power. (It does depend on diameter of course.)

Cheers

Phil Hobbs

Could still have done worse, though:

Anyone who can't write a mu that can be distinguished from a 'p' shouldn't use post-it notes. Consider using a label maker.

Larkin's right. You shouldn't be an EE.

They're merely demonstrating their area of competence.

But something that would be quite useful. Manufacturers give C/V curves (both AC and DC) but that doesn't help much with simulation.