Search found 24 matches

by rocket scientist
Fri Jan 07, 2005 1:45 pm
Forum: General Discussion
Topic: Zener Diode Question
Replies: 10
Views: 2653

Re: Zener Diode Question

jrcfg:<p>No, you did the calculation for a 30 Volt drop across the resistor, which is not the case. <p>Diodes are confusing because they are nonlinear devices that do not follow Ohm's law. To a good approximation the voltage drop across a diode is constant, independent of the current through it. In ...
by rocket scientist
Thu Jan 06, 2005 9:17 pm
Forum: General Discussion
Topic: amperage or current
Replies: 24
Views: 5484

Re: amperage or current

I am glad no one is using 'shortage' for anything!
by rocket scientist
Wed Jan 05, 2005 10:15 pm
Forum: General Discussion
Topic: Voltage follower with variable offset?
Replies: 13
Views: 3221

Re: Voltage follower with variable offset?

Ron H's solution reminds me of the pre-digital days when op-amps were amplifiers used in analog computers for arithmetic operations -- in this case subtracting 5. Hence the name op-amp, of course.
by rocket scientist
Wed Jan 05, 2005 10:00 pm
Forum: General Discussion
Topic: amperage or current
Replies: 24
Views: 5484

Re: amperage or current

The original topic is my comment on H&H. I would like to add two more to the many really good recommnedations on reading material:<p>1) "Feynman Lectures on Computation" Feynman is a Noble prize winner (he invented quantum electrodynamics) and if you want something by a smart guy who thinks clearly ...
by rocket scientist
Wed Jan 05, 2005 9:28 pm
Forum: General Discussion
Topic: How to measure a mechanical vibration frequency?
Replies: 11
Views: 2577

Re: How to measure a mechanical vibration frequency?

For those of you interested in using Fourier Transforms to find the audio 'signature', you should take the square of the magnitude of the Fourier Transform. This gets rid of the phase of the signal, and leaves you with something proportional to the power spectrum. However, to get this to be useful, ...
by rocket scientist
Wed Jan 05, 2005 9:15 pm
Forum: General Discussion
Topic: How to measure a mechanical vibration frequency?
Replies: 11
Views: 2577

Re: How to measure a mechanical vibration frequency?

Audio is easy to digitize with a sound card in any laptop computer for frequencies up to 20 kHz.<p>Contrary to what Smith said, you can detect anomolies with processing that your ear will never hear. Signals can be integrated for 100's of seconds with computer processing to bring out a weak tonal, b...
by rocket scientist
Tue Jan 04, 2005 5:20 pm
Forum: General Discussion
Topic: How to measure a mechanical vibration frequency?
Replies: 11
Views: 2577

Re: How to measure a mechanical vibration frequency?

Have you tried microphones? It is simplicity itself since it doesn't have to touch anything. You could use several placed at key locations. You could even use a wireless audio transmitter for the harder to reach spots. I would recommend looking for changes in long-time power spectra with lots of ave...
by rocket scientist
Tue Jan 04, 2005 4:58 pm
Forum: General Discussion
Topic: amperage or current
Replies: 24
Views: 5484

amperage or current

I believe the best electronics book around for anyone who really wants to know how all this stuff works is "The Art of Electronics" by Horowitz and Hill. An interesting quote from page 4 : "don't call current 'amperage'; that's strictly bush-league". There are over 1100 pages, most of them very enli...
by rocket scientist
Mon Jan 03, 2005 10:11 pm
Forum: General Discussion
Topic: weighing vs. weighting
Replies: 3
Views: 1025

weighing vs. weighting

The Jan issue of N&V talks about voltages that are weighed. Voltage has no mass and therefore it cannot be weighed. But voltages can be weighted using various circuit techniques, e.g. a weighted average in an op-amp.<p>Just because we are technologists don't mean we shouldn't use English good!