I fear you overlooked something.
They state clearly : "The first system was able to lift a weight of 3 kg using an electrical input power of only 16 W. Based on the surface area, a lift capacity of 11.5 kN/m2 was reached."
11500/30 ~ 380; 16W* 380 ~ 6000W, so even assuming peripheral losses...
There are special lamps for precision measurements in photometric, for example this one:
I´ve found one source for emissivity of tungsten here:
If you expect high accuracy in...
I replied to a similar question here
about two years ago.
Maybe i was a bit unfriendly, but things haven´t changed much since then. Most of the technical information I linked to is in German, so you´ll have to translate.
As jtbell points out, some of the first railroads started with animal traction, at least in Europe.
(sorry, no English version available).
Steam locomotives soon...
You might try evaluating the output of a proportional counter using a very sophisticated digital storage oscilloscope, but that would be a lot of effort and probably not worth it.
I used a mercury diffusion pump (quite) some time ago. With a bit of heating the vacuum got down below 10-5 torr.
Of course there was a cryotrap between the pump and the vacuum vessel (liquid nitrogen).
If this is about safety (outside of a purely experimental setting) you better check the codes and regulations applicable. Probably there are a lot of them.
You will find that there are standard circuits designed to comply with the codes. Just find out and use them.
Don´t try to cut costs or to...
You´re perfectly right about the pinhole.
The standard way of producing a parallel beam used to be:
Use a lens to produce a (reduced) image of your light source onto/into a pinhole. Try to capture as much of the light as possible.
On the other side of the pinhole, use a lens to produce your...
In theory you are correct with a 20db conversion factor.
But it applies only for a point source, far field conditions and negligible influence of the measuring microphone, and you cannot assume all of that. You can only use the 20db as a sanity check.
Yungman is essentially right: you are...
A headphone/earphone driver needs to produce sound pressure in the ear only, so it is tested on an ear simulator (a small, short tube, you can find the details in the datasheets in the links you gave).
A "normal speaker" is expected to produce sound everywhere around it. Apparently this needs...
The speakers you linked to are for headphone/earphone use, forget about them. (The db numbers don´t mean the same as in normal speakers).
You need size for a decent midrange, don´t go below 30mm diameter if you can. (A cordless phone phone I repaired a few weeks ago has a 36mm speaker for...
Quite a few deep freezers heat the sealing surfaces to prevent buildup of ice. But I´ve never heard of one using electromagnets. As vk6kro said, the magnet in the door seal is strong enough.
I disassembled seal once and found a strip of magnetic material all along the seal.