Hi all,

I have to connect THREE(3) dosing pump analog inputs to ONE(1) PLC analog output. The module SM1234 is good for a maximum of 600ohms on 4-20mA output. The dosing pumps are 200ohms each. 

The question is, what happen if the impedance exceed only by a little the maximum of 600ohms? Is it a no go and i should buy another analog module or it will be fine if i don't need laboratory precision?

Thanks!

Hi, 

If you use the output as 4-20mA loop and go above the maximum loop resistance,  the output will be overloaded and possibly damaged. (P = I²R). 

See the SIMATIC S7 S7-1200 Programmable controller on the page 914.

Always try to comply with manual!