1. Quote of the week: "If you think nobody cares if you're alive, try missing a few loan payments" - unknown
Source: Wikimedia
2. New quiz AQQ285 about the analog voltmeter expertise
We are back to our fundamental area: electronics...
Sources:
https://upload.wikimedia.org/wikipedia/commons/0/01/Galvanometer_scheme.svg
https://cdn2.picryl.com/photo/2015/12/24/spiegelskala-1-b45d8a-1024.JPG
We all remember from our first electronic lab, the use of analog multimeters to measure voltages, currents or resistances.
They are based on the galvanometer invented by d’Arsonval in which the interaction of a current (to be measured) with a permanent magnetic field moves a needle in front of graduated scales.
Due to mechanical inertia, the current measured is only sensitive to its average value.
Therefore measuring AC signals, like for example pure sinewaves, will indicate zero normally. Multimeters overcome this by rectifying the AC signal before to be measured.
The average value obtained is somehow fake since the original signal has been altered. However, such biased measure can reflect the RMS value of the signal.
This is why a second scale called “AC” mode, usually flagged in red, is calibrated to give the RMS value. However, such scale is only valid for pure sinewaves.
Questions:
1. That “AC” scale is slightly different vs the “DC” scale. The factor is around 1.11
How is it determined?
2. With the same voltmeter defined above, if you enter the following periodic signal, what are you going to read in the AC scale?
Good luck and try to be among the first ones...
P.S. As usual, please spread the quizzes among your friends and colleagues!
