source problem at mV and mA

Hi everyone,

I m a Keithley 2612 user and I can give as current or voltage when Volts or Amps.(for example 1 V, -1 V , 1 A) but when I want to source 200 mV or 20 microamper device does not work. I think I have a range problem but I cannot solve it. If you had similiar problem, please share your experience.

Thank you.