[Test-Equipment] Cosel K150A-12 Power Supply

[Fred Olsen]

Arthur, as has been pointed out those terminals are indeed for remote 
voltage regulation sensing.  There are a couple of fine points for 
implementing remote sensing which should be mentioned.

In general, use twisted pair for your load lines.  16 Ga. is sufficient 
for this supply.  Use shielded twisted pair for the sense lines. 
There's a note regarding gauge on the below-referenced data sheet but 
common 20 or 22 Ga. STP instrumentation cable will work fine in most 
cases.  The 100% shield foil stuff with a drain wire works the best; the 
sense circuit must be kept quiet.  Ground the shield at one end only, 
usually the PS.  Note that the sense lines should use a Kelvin 
connection at the load.  Don't cheat and tie them to the load lines 
further back.  Avoid switches, relays, and connectors in the sense 
circuit if at all possible.

This next is so obvious that "it goes without saying".  Having seen it, 
I'll say it.  When using remote sensing the local sensing jumpers 
between the V and S terminals must be removed.  Both of them. (Saw that 
too.)  Without remote sensing they must be in place.

In any application of remote sensing the following is important but 
seldom mentioned.  Make certain that your power supply has sensing 
protection diodes at its output.  If the remote sense circuit suffers an 
open for any reason the supply will drive to maximum possible output 
voltage.  If your load can stand whatever that may be, good for it.  If 
not, a cheap pair of 4000-series diodes will save your bacon by limiting 
the output to one diode drop above the set point.  Check the schematic, 
if the Malaysians gave you one, or visually inspect for the presence of 
a pair of diodes, one between each set of V and S terminals.  Or they 
might be the 'last thing' on the board before the output.  I suggest 
adding them if they aren't there.  They are arranged thus: anode to S- / 
cathode to V-, and anode to V+ / cathode to S+.
Sometimes resistors, on the order of 100 Ohms, are found as sensing 
protection.  Diodes are preferable.

Here's a handy poop sheet on remote sensing, from 'the company formerly 
known as HP'.
http://www.measurement.tm.agilent.com/hints/5965-8239E/hint01.shtml

Those who don't consider themselves expert in power supply application 
would do well to find a copy of HP App Note 90B, "DC Power Supply 
Handbook".  An oldie but goodie.

Best of luck with the project,
Fred
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