I’m working with a logix 5000 system that’s configured with a lot of flex racks. So on 1794-IE8/B analog input card, how do you determine when to configure a channel on that card for 4-20ma vs (0 to10 V) / (0-20ma)?
While offline, double click module on left project tree under I/O (or right click select properties), then select config tab. (See picture)
It depends on what your sensor puts out. when you purchase sensors, you can decide 0-10v (analog voltage out )or 4-20ma (analog current out). 0-10v is simple, cheaper and easier to troubleshoot, but is also more susceptible to electrical interference and in long wire runs, voltage drop.
The 4-20 milliamp signal/sensor is less susceptible to both noise and voltage drop. If a 4-20 ever goes to 0ma, something is wrong. with a 0-10v, it could be sensor at lowest setting or something wrong. Thus your software defaults to 4-20ma, but if you have an older 0-10v, you can change the setting.