In Reply to: 4-20mA posted by Spide on 10/14/02 at 1:46 PM:
all you need is a dual opamp and few mfr ressistor an a couple of trimmer and a reference.
close the input current source with a 250E resistor ther by 4-20 ma current is converted into a 1-5v source followed with a opamp buffer , config a opamp as a scaling circuit , in the summing node add a ref of opp polarity to offset the 1v and use the trimmer in the feed back to get desired span of5v
out may be stapped to a zener clamp to limit the negative excursion to -0.6v in the event input open
for more detail write back