In article , Iain M Churches
wrote:


The phase measuring equipment to which I have access is built by
Feedback Electronics in the UK. It can be used in two ways, depending on
whether or not you have the additional digital meter for direct readout.

[snip]

If you have the digital readout unit, measurement is even simpler, and
the oscilloscope is not required.

Connect output 1 from the oscillator to input 1 of the meter unit.
Connect output 2 to the device under test. Connect the output of the DUT
(via a dummy load if required) to input 2 of the meter unit. The latter
can measure the phase angle between a pair of signals with a 30V
difference, so a 60W amp can be measured with ease.

A led shows which signal is lagging or leading, and the digital readout
gives the phase angle. Easy and fun:-)

The above should work OK, although Arny's method has the advantage that if
you use a wideband signal you can recover the phase and amplitude response
across the relevant band in one measurement. This can save lots of time by
avoiding having to make loads of measurements, frequency by frequency, and
then plot the results.

FWIW I would tend either to use a sampling scope that can do FFTs
(equivalent to the method Arny describes), along with a noise/arb-gen, or
use a PSD (equivalent to what you describe) and sine-gen depending on what
is convenient. (And, these days, what kit my ex-students will allow me to
'borrow'. ;- )

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html