Using a SMU as a variable resistor/How to DIY a 1A potentiostat?

[jogri]

Hi guys,

is it possible to use a SMU to remotely control a power supply that correlates a resistance to a voltage? The power supply is outputting a fixed current of 1 mA (on the remote programming port) and is meant to be connected to a resistor (1 k per V) to control the output voltage. Am i missing something obvious or can i just hook up my SMU and tell it to sink the equivalent of 1k * 1 mA (if i want 1V)?

Why would i even do that when i have a SMU? I need an output current of 1 A, and my Keithley 236 can only deliver 100 mA. My Power Designs 2020 on the other hand can output  2 A, and its output voltage can be controlled remotely (and i can switch the polarity of the output with my 34970 and a few relays).

What do i want to do with it? Use it for cyclic voltammetry, that means creating voltage vs current plots in the range of +/- 5V. The voltage is applied in the form of a triangle wave (@ a few Hz), the current is measured simultaneously and plotted against the voltage. I am currently just cranking the voltage up and down manually, but this is less than ideal since there is a lot of time for electrolysis to happen (we are talking about 10 min per cycle).

Alternatively, can you recommend a circuit design that can output a +/- 5V signal @1 A? Normal DIY potentiostats just use the output of an op amp since they rarely need more than 1 mA, but since i also need a negative output voltage i can't just use the opamp to drive a transistor that can handle this current (i'm probably missing an obvious solution).

(For anyone wondering why i need 1 A for a CV: I am working with molten salts, and they are rather good conductors...)

[julian1]

Use a signal generator for a -5 to +5V ramp, add a bipolar push/pull emitter follower for 1A, then add a current sense resistor, and plot current against voltage on a scope? Anything more complicated, and you begin to replicate the smu function.