SLC 5/04 Programming

I need to have 4 different voltage selections available at 4 different contactors. example I am using a motorized variable transformer(variac); 120 volt motor turns and increases the voltage and reverses and decreases voltage.
what I planned on doing is having 3- voltage transducers that send 4-20 ma to my plc and average these inputs to have one register N7.1 for my input.
using this for control I would have a selector switch for my different voltage selection "setpoint" say 208 and have a les,grt block control my descrete "relays" to get to the desired voltage level then have a equal block latch a bit and lock out control to the variac until it gets out of a certain range then start controlling again.
is this the best way to acomplish control of (2) descrete outputs with analog in?

M,

"Best" is what works for you and all that will come in contact with the program. But it sounds like you have a method to Increase/Decrease the voltage at the contactors, using an analog input feedback voltage.

Question:
Do you really need to average 3 voltages to produce one feedback input? Is the averaging done to offset large differences in a 3-phase power supply?

Beside the point, but WHAT in the world would require 4 different voltages? Is this some type of testing equipment?

Lancie1,
Thank you for the reply. The reason I am averaging is because I will be using single phase to one one of my contactors and the rest will be 3-phase,so on the 3-phase if I only look at two of the legs if I lost a leg this would be bad since I think the voltage level is good.and you are correct ths is a testing station.(actually I will use one variac two feed two seperate stations with 4- contactors per station and I will interlock these stations)
It would be a lot simpler to just have a voltage trasmitter I agree, I would just not be able verify that all three phases are present.