"Andy" wrote in message
...
Hello,
I am working with an instrument which outputs 0-5mV, and that signal
has to reach a sensing device 35' away. I am concerned with noise,
and I don't think shielded cable will work well enough. So I am
considering using coax cable. But I don't understand coax. There are
numerous "RG" ratings and ohm ratings. Suppose I used RG62 with 50
ohm terminations. What do I need to know about the termination and
the cables in order to properly use this? What's the difference
between RG62 and say RG59? What are the ohm ratings referring to, and
what terminations would I need for an ohm rating of 50? Is there a 50
ohm load which gets put somewhere in the system? Clearly I have many
questions. Any help would be appreciated.

thanks
The RG terminations refer to the RADIO FREQUENCY and pulse properties of
the line. If you are only measuring voltages which change slowly (not more
than 50Hz components) ANY coax will do. Think of it as a screened test lead
( of course you should earth the outer screen)
Hope this helps
P.W.