[Test-Equipment] Using an HP 331A Distortion Meter

[David DiGiacomo]

On Tue, Sep 2, 2014 at 2:07 PM, Barry <n4buq at knology.net> wrote:
> I'm a bit new to using a distortion meter and have a basic question.  When connecting the device I want to test to the meter's input, I assume it is necessary to terminate the generator properly (e.g. into a 600-ohm resistor, etc.) and that's so that the generator sees the proper load.
>
> What's confusing me a bit about this I may use this to measure distortion for a 600-ohm-terminated signal as well as connecting it to the 8-ohm load for the PA output.
>
> Does the meter not really care what impedance it sees on the input?  It just seems odd that I would feed it a 600-ohm load in one case and an 8-ohm load in another.


The distortion analyzer has a high impedance input, so it doesn't care
what the source impedance is, as long as it's not too high.

However, the distortion of the source will vary depending on how it is
loaded, so you should connect the load that is relevant to your
application (or if you are testing against a specification, the load
that is specified as a test condition).