Function Generators

Basically you need to create an analog signal that changes over a certain range in 160 steps. If you read your power supply manual, you'll see that it can be programmed with an analog input - applied at the connectors in the back - at least i believe it can in voltage mode, you'll have to verify that it can in current mode. Just calculate the two voltages you need to drive 250 and 90 mA, then program the function generator to generate a stairstep waveform, in 160 steps. You may need an additional generator to create the 1Hz pulses to drive the arbitrary function generator.

What do you mean by 160 steps I tried reading the manual but I really don't understand mostof the stuff it says there.

It sounds like you are using a Voltage output to provide the current and without a large load on it's output it takes a long time to disharge the output filter cap. I assume that the voltage source doesn't have a current limit adjustment.

You could leave the Voltage adjust to a level that provides 250mA and use a switch to take your 250mA from the output jack and the Voltage that produces 90 mA from the tap of a voltage divider across the output of the supply. Flip the switch once per second.

If your Agilent function generator can be set up to offset the DC to the voltage for the 90mA and jump to the voltage that provides the 250mA and back again every second that would be cool. I don't think it can do the current, offset or repetition rate. Check it to make sure.

I would be interested to know what the two currents are being used for.