24-08-2012, 01:52 PM
Yup - that would work, although in practice using bridges can be tricky (issues with grounding or strays).
Rather than a 'scope, I'd prefer to use a so-called "True-RMS" DVM, providing I know that I'd be measuring at a frequency that is appropriate (good DVMs will specify their frequency range), as a DVM will be an order of magnitude more accurate. But I'd still observe on a 'scope to ensure there is no clipping or other distortion. Seeing is believing, after all
To be honest, the R-loss method under discussion here is fine, and is normally the most convenient way to measure a substantially-resistive Zin. It works equally well for Zout, providing Zout isn't very low (like you'd see on an audio power amplifier) - although in practice it's just a case of having enough resolution when you take the before and after voltage measurements...
Mark
Rather than a 'scope, I'd prefer to use a so-called "True-RMS" DVM, providing I know that I'd be measuring at a frequency that is appropriate (good DVMs will specify their frequency range), as a DVM will be an order of magnitude more accurate. But I'd still observe on a 'scope to ensure there is no clipping or other distortion. Seeing is believing, after all
To be honest, the R-loss method under discussion here is fine, and is normally the most convenient way to measure a substantially-resistive Zin. It works equally well for Zout, providing Zout isn't very low (like you'd see on an audio power amplifier) - although in practice it's just a case of having enough resolution when you take the before and after voltage measurements...
Mark
