Hi Rex,

"Rex" wrote in message
...
Here's a link to one manufacturer
http://www.microlab.fxr.com/pdf/HX,HY,Hzseries.pdf

Yep, that's them alright. The one we have is the electrostatic version.

I took a closer look over a wider frequency range at its response and -- not
too surprisingly -- it's a straight line on a log-log plot (i.e., the coupling
is almost purely capacitive).

Thanks for everyone's help,
---Joel