Keithley single output variable bench dc power supply keithley 2440 the keithley 2440 is a single output variable bench dc power supply source measuring unit smu from the 2400 seriesthis instrument has been designed specifically for test applications that demand tightly coupled sourcing and measurement the 2440 provides precision voltage and current sourcing as well as measurement capabilities the instrument is a true 6frac12 digit multimeter and a highly stable dc power sourcethe po