open-chassis +/- power supply connections: +S and -S

Discussion in 'General Electronics Chat' started by Lambda, Apr 19, 2012.

  1. Lambda

    Thread Starter New Member

    Feb 28, 2011
    28
    0
    So, I have this old open-chassis power supply that supplies +/- 12v. It is stamped with the number pr2329, and was manufactured in 1987. Its outputs are a bit odd, though. They're divided into 3 sections. The + section has "+s and +out". The - section has "-s and -out". The com section has +s, -s, and com.
    The way it was wired when I got it has the out and s connections connected together, and the +s, -s, and com all connected together, and it seems to work well this way.
    What is the purpose of these S connections? Why are they connected together? When would one want them separate?

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  2. #12

    Expert

    Nov 30, 2010
    16,284
    6,797
    The S stands for "sense". When the output has to travel through a long wire and the voltage at the load is like, 4.85 instead of 5.0 volts, you seperate the sense terminal from the output terminal and run a seperate wire to the load. This new wire reports the true voltage at the load to the error amplifier (at the terminal marked S) and the power supply boosts the out put voltage until the LOAD gets 5.00 volts instead of the WIRE getting 5.00 volts.

    The red jumpered and black jumpered terminals look obvious to me but the triple grey doesn't look obvious to me. Results: partial answer.
     
    Lambda likes this.
  3. Lambda

    Thread Starter New Member

    Feb 28, 2011
    28
    0
    Oh, wow, that's useful. I REALLY could have used that a couple months ago.
     
  4. #12

    Expert

    Nov 30, 2010
    16,284
    6,797
    I guess you could have a voltage drop in the current carrying wire to COM and thus use the sense terminals in the triple grey section but I'm apparently having a senior moment and can't remember how to use that.

    edit: Think of two completely seperate loads with Kelvin connections and I can work out the wiring, but I'm eating supper right now.

    OK. Try this.
     
    Last edited: Apr 19, 2012
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