Roy Lewallen wrote:
John Popelish wrote:
I wish I could, but this is the first I have heard of such
instrumentation. That is why I would like to read more about it.

Hopefully the poster mentioning the optical probe will explain a bit
more. But I recall seeing optically coupled instrumentation used in an
EMI screen room to couple signals in and out. To my knowledge, though,
the probes themselves were conventional, and fiber optics were used
only to replace connecting wires.

Such probes are routinely used for RFI, RF hazards and screened-room
measurements, where connecting wires would disturb the fields or act as
pathways for RF leakage.

They do have a disadvantage that might be relevant to this discussion:
because the probe head has to be self-powered, and has to include some
kind of encoder and optical transmitter as well as the normal current
transformer, the battery and extra area of PC board will increase the
probe's self-capacitance.

A different kind of fibre-optic probe is used in basic research on RF
hazards, to measure very localized and very small temperature changes in
simulated human heads and bodies. These microprobes are purely optical,
and are sensing some temperature-dependent optical property of liquid
crystals(?) at the probe tip.


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek