-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 The Friday 2008-02-15 at 15:56 -0500, James Knott wrote:
I don't think you can measure true rms with a coil and needle. :-?
It was measured by thermal effects...
There are electronic true-RMS voltmeters with analog readouts. For example, the Balantine 323 has a nice big dial. You would have to measure the voltage drop across a known value shunt resistor in series with the load, and calculate the power from voltage and current.
Ummm... He was talking about RMS, which implies voltage or current. There's no such thing as RMS power.
Well... you have to multiply voltage with current, around the cycle, and integrate. If they are 90° out of phase, result is zero. If current is switched, who knows the result! I mean, those chips should know, but I don't know if they know, if you follow me :-) - -- Cheers, Carlos E. R. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.4-svn0 (GNU/Linux) iD8DBQFHthWitTMYHG2NR9URAsCtAJ9kLQAvnFj3LHGbmfZ4opQcRDObkgCffAU/ ufQopS1zIK4C4ueEW2NxirE= =/4Pv -----END PGP SIGNATURE-----