Nerd humor
Every now and again in browsing the internet for work related trivia i.e. I stagger across one of those gems of engineering documentation that make me blink in amusement at the morbid joy we seem to take in working with things that will either fry us, bake us, or make us go splat when handled incorrectly...
zapped - you are playing with line voltages here and there is not much
between you and eternity...'>
quoted from a very pithy discussion of how to build a variety of cheap-ass capiticance measuring circuits for use in fixturing. full page if you're actually curious
---
Cheapest way (to measure capacitance): you can make a voltage divider:
|------------------------------
| |
| resistor
| |
120 volt AC (wall plug) |
| |
| capacitor
| |
|------------------------------
Measure the voltage across the resistor and the capacitor. Don't get
zapped - you are playing with line voltages here and there is not much
between you and eternity.
C = (Vr / R) / (2 x pi x f x Vc)
where Vr is the voltage across the resistor, R is the resistor in ohms,
pi is 3.141, f is 60 Hertz (or 50 in some countries - you know who you
are), and Vc is the voltage across the capacitor.
Please note that you have to actually measure Vr and Vc. You can
*not* assume that Vr+Vc=120 since there is a current phase shift
through the capacitor.
By using the existing 120 VAC line voltage we let the power company
supply us with a rock-solid 60Hz low impedance voltage source. For
free!
zapped - you are playing with line voltages here and there is not much
between you and eternity...'>
quoted from a very pithy discussion of how to build a variety of cheap-ass capiticance measuring circuits for use in fixturing. full page if you're actually curious
---
Cheapest way (to measure capacitance): you can make a voltage divider:
|------------------------------
| |
| resistor
| |
120 volt AC (wall plug) |
| |
| capacitor
| |
|------------------------------
Measure the voltage across the resistor and the capacitor. Don't get
zapped - you are playing with line voltages here and there is not much
between you and eternity.
C = (Vr / R) / (2 x pi x f x Vc)
where Vr is the voltage across the resistor, R is the resistor in ohms,
pi is 3.141, f is 60 Hertz (or 50 in some countries - you know who you
are), and Vc is the voltage across the capacitor.
Please note that you have to actually measure Vr and Vc. You can
*not* assume that Vr+Vc=120 since there is a current phase shift
through the capacitor.
By using the existing 120 VAC line voltage we let the power company
supply us with a rock-solid 60Hz low impedance voltage source. For
free!