On Sat, 13 Mar 2010 05:51:01 -0800 (PST), Andy wrote:

On Mar 13, 4:21Â*am, "William Sommerwerck"
wrote:
"William Sommer****** Fool "
5mV is down in the range of microphones and phono pickups.
I would not run such a signal through 35' of coax.

Looks like I spoke too soon.

The signal is DC from a instrument, a pyranometer.

That anything like an optical pyrometer? IOW a thermopile?

The output (0 to
5mV) is going to be scaled by 2000 to get 0 - 10V into a data
acquisition card. My concern is that having a signal in the low
millivolt range, and a cable of some 30-50' (exact length is not yet
known), noise would be a problem. This is a residential project, and
so there is no heavy machinery to speak of. Although I know this guy
has a shop and uses a lot of standard shop tools. So, my decision to
use coax is based on the fact that it's easy to make good field
connections and it "appear" to have better noise immunity than
shielded. There is a braided shield in coax; only a foil shield in
most shielded pairs.

A balanced, shielded cable to the instrumentation amp is standard
industry usage. Common-mode noise pickup is rejected. Nothing
wrong with Beldin cables with foil shield.

Grant.