[SOLVED] Current Limiter Circuit w/ constant voltage

[krixen]

Hello all,

I am trying to design a current limiting circuit that supplies a constant voltage across the load. If the load resistance were to drop to close to 0, (i.e. shorted) then the current supplied to the load would not exceed a set limit.

For some background, I am trimming high precision potentiometers and in order to do this, as i trim the pots (changing the resistance either up or down) i need a constant 10 volts across the load. It can vary in the .1 mV range but no more. Every once in awhile you accidentally touch one of the leads to the wiper directly and it causes a short which draws in a high current and can damage the pot very quickly.

Some parameters:

I load max = ~50 mA
V load = 10 mV +/- .1 mV (as the load changes in resistance)

Any suggestions or help? Thank You

 

[crutschow]

You can add an electronic current limiter to your voltage source. What is the source?

 

[krixen]

Just using an ideal 10 volt battery as my source, i want to be able to simulate it first before i buy parts.
When i make it in the real world i will be using an agilent DC power supply, E3663A

 

[E-design]

Perhaps you can adapt this circuit to work for you. R2 should be a 5W resistor if short circuit is present for a long time. Current will be limited to just over 50mA.

 

[crutschow]

I could find no info on the Agilent DC power supply, E3663A. Is that the correct number?

What does it have for built-in current limiting?

Does it have a 4-wire output option on the back?

 

[krixen]

I meant E3633A, sorry about that. I will try the circuit you posted however it needs to be extremely fast, once the
pot is shorted the current needs to be diverted away very quickly.

- - - Updated - - -

I have made this simple circuit diagram to kind of help clarify a little bit of what i am trying to do.
I constantly need 10 volts across the pot in the picture. This is the most problematic part because any type of circuitry you put into the
limiting circuit, once i trim the pot and the resistance changes, the voltage across the load will vary.

The circuit i use now to trim them is the picture without the dotted box. No matter what the resistance changes, the voltage is always 10 volts.
The pots can change heavily in resistance and each one may have a different resistance, (i.e 10k or 150k).

 

[crutschow]

The E3633A has a built-in adjustable current limiter. Why not use that to limit the current?