Power Supply Sense Circuit Protection

[toddwmps]

I have a fuel pump tester with a power supply that has a sense circuit for automatic voltage compensation. The power output is controlled by a remote switch to the power supply so there is no switch in the main circuit itself. My problem is that the sense circuit cannot be connected to the pump if the main power circuit is not energized. The only time that this could be an issue is if the fuse (15A) in the main circuit blows. Is there some device or relay that will connect the sense circuit only when the main circuit is energized? Thanks.

Power Supply:

http://www.bkprecision.com/products...tching-dc-power-supply-with-remote-sense.html

Manual:

http://www.bkprecision.com/downloads/manuals/en/1693_1694_manual.pdf

 

[OperaHouse]

Two suggestions:
1. Don't sense after the fuse
2. Don't use a fuse

I find it hard to believe a digital supply doen't have adjustable current limit? What exactly is the problem you are trying to prevent. What is wrong with the 5A supply current limit?

 

[toddwmps]

The max current on the main circuit is 30A. 5A is the AUX output limit which I am not using. When testing fuel pumps I will see 10A-12A at most. I would like to avoid anything above that just in case something goes wrong. I would rather not have sparks or excess heat around a flammable test fluid.

Sensing before the fuse would work, but I'm seeing a drop of 0.1V across my current fuse which would partly defeat the purpose of the automatic voltage compensation.

 

[OperaHouse]

Normally you can place a 100-200 ohm resistor on the load side of the fuse. This goes to the sense. On the source side of the fuse place a diode + side to sense. Should the fuse open, voltage only goes up a half volt. A small amount of current still goes to the pump.

 

[toddwmps]

I think I'm just going to take out the fuse. I've honestly never blown it and according to my boss that did the design on the original equipment the fuse was originally to protect the power supply and not the pump. Thanks for the help.