Archive for category how-to

Radiometric Measurements

It’s easy to confuse the units of LED light output. Steradians, luminous intensity, etc.

Here’s a link to an application note that explains these well, written by C. Richard Duda of UDT (now part of OSI Inc.).  Apertures, intentional and otherwise, are discussed, along with typical test configurations.

Link to pdf of application note titled Radiometripdf of Radiometric and

Please tell us if the link gets broken!

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CCD Cameras, eyes, and physics

This tech note was motivated by the question – how does the response of our eyes

differ from the response of a CCD camera sensor.

Using the data of a particular Hammamatsu CCD camera as an example,

we compared how silicon ‘sees’ to the photopic eye response

and compared both to a Planck black-body curve of a light at a particular

color temperature.

We don’t know what those lumps are in that CCD response curve – maybe some

strange reflection interference??

If you know – tell us!


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Vision response vs. Planck’s Black Body Curve

Color temperature is based upon the idea of a Planck black-body radiator.

Here’s a Tech Note that shows how our eyes respond to the Planck Black-Body radiator.

For a lamp filament at a certain ‘color temperature’ there’s a curve of how our eyes

respond to the lamp. Pete put this into a MathCAD model, and there’s a pdf here

that shows off a few nice graphs.


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attenuators, connectors, etc.

Here’s where to get quality attenuators and connectors

Testing any high gain low noise amplifier requires a nice clean attenuator.

You need to drop the level of your function generator,

or that x1000 gain amp would need to supply 100 V output.

Pasternack Enterprisese sells a nice 30dB atten for about $42.

Their part number is PE7000-30.

If you put 2 of these in series, you have about x1000 attenuation.

(These assume a 50 Ohm load, so buy one of those too).

Here’s a link to their website:

Pasternak weblink

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Actinica Book List

Ok, we have a book problem.

Both of us waay like good engineering books. A good explanation, or a great

graph that sums up why that camera ‘sees’ differently than my eyes, etc.

Since we’re always stumbling on more good books, this list will grow.

Drop by later see what’s new.

Here’s some of the books we like, as a pdf file here,


and here’s some more books we like:

  • the Feynman Lectures on Physics, a 3 volume set. Here’s a guy who can explain anything well. Like how sine, cosine and the magic number e all relate to the imaginary number i (square root of -1). He also has a great description of how a ’50 Ohm’ transmission line acts like ’50 Ohms’ no matter how long it is. For a really great puzzle – read his description of how charging a capacitor really involves magnetic fields outside the cap’s plates.

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