+/- voltage with two DC Power Supplies

[requim]

Dave made a reference in his blog when he was attempting to change his HP e3610a from 115V to 230V that if he had two of them he would be able to run one with positive voltage and the other with negative voltage.  I find myself in a situation where I need +25V and -25V to test a device but none of my supplies supports negative voltage.  How can I do what Dave was talking about?

[gxti]

Are the supplies isolated? (high impedance between the negative terminal and mains earth). If so, connect the positive of one supply to the negative of the other supply, this will be your ground. Then the free negative terminal is -X volts and the free positive terminal is +X volts.

[requim]

I assume they're high impedance.  I've check before I do anything.  I have two HP e3610a's, an Agilent 6611C, and a Agilent e3620a.  I was hoping to be able to do it with the e3620a because it has dual +25V which is what I need.  Will I be able to do it within the same PS or will I need to get yet another PS to get me up to 25V and use that with the e3620a?  None of my other power supplies go up to 25 volts.

[jimmc]

Referring to the E3620A manual (page 3) http://cp.literature.agilent.com/litweb/pdf/5968-9727EN.pdf

The 50-watt E3620A dual-output
power supply provides two 0 V to
25 Vdc outputs with the maximum
current of 1 A to satisfy most bench
requirements. The outputs are
completely independent and isolated.

and from the spec.  table

Isolation 240 Vdc

So the two outputs may be connected as you like and in fact may be connected in series other power supplies so long as the total voltage does not exceed 240v

Jim

[Richard W.]

+/- 25V is possible with your E3620A.

There are practically two isolated power supplys inside the case. It's all about voltage potentials.
Just connect the negative terminal of V1 with the positive terminal of V2 these two connected terminals are your 0V for the circuit.
Set the Voltage on both chanels to 25V. And you're done.
+25V are on the positve terminal of V1, -25V are on the negative terminal of V2
0V is on the two connected terminals.

You can verify it with a multimeter.

[requim]

Many thanks.  Learned a few things.  Can you tell me in the same manual it lists the control modes for the e3610a as CC/CV which I understand to mean Constant Current/Constant Voltage, but for the e3620a it lists CV/CL.  I know CV = Constant Voltage, but what does CL mean?

[IanB]

Many thanks.  Learned a few things.  Can you tell me in the same manual it lists the control modes for the e3610a as CC/CV which I understand to mean Constant Current/Constant Voltage, but for the e3620a it lists CV/CL.  I know CV = Constant Voltage, but what does CL mean?

I located and read the manual for the E3620A here: http://cp.literature.agilent.com/litweb/pdf/E3620-90001.pdf

It says that the two outputs are completely isolated and each has independent voltage limiting and current limiting controls. It further describes how the outputs may be connected in series for more voltage, or in parallel for more current.

However, I do not see any reference to CV/CL. Since I don't see this described in the manual, I am at a loss as to what it might mean.

[requim]

@IanB -  I think you answered my question inadvertently.. I think CL = Current Limiting.  The CV/CL shows up in the brochure linked to by jimmc earlier in this thread.  It's in the table under Features and also under Control Mode.