what exactly you want to do?
measure capacitance on production line for example? how accurate? how fast? what is the budget?
there are ready devices for this job (Agilent etc. just use use google) but if it was me, i would try to use serial connection and just stick multimeter in the panel. is S5 maybe without serial interface? (maybe it's used already...?)
if required accuracy is not very high, (standard capacitors in this range are usually some kind of electrolytic and have very poor tolerance, specially the Aluminum type...). i would just make my own circuit, it could be very simple (for example constant current device is just two $0.50 components, use one relay to to turn it on, when off discharge capacitor through resistor, and don't forget to write the plc code...).
micorocontroller projects for example often use single I/O pin for this (on PLC that would be one input + one output),
the other way is to make external oscillator (again sub $1 project...) and count freq. etc (frequency can be converted to voltage if you are really stuck on analog input...).