Micrologic 1400 AI/AO

[BrettL]

I had a question regarding the Micrologix 1400 AI/AO's. I have a 4-20mA AI wired to an input channel (I:3.0) and I am moving that value to an output word (O:4.0). When I monitor the output current it is always half of my input current? I used a MUL block to double it and it works effectively it just does not seem right to me. Any suggestions would be appreciated.

*I want to use this PLC to receive this field signal and then pass it along to another controller.*

 

[Old No. 7]

Probably scaling. If you have a 1762-IF4 and it's set to for Scaled for PID it would give you 0-16383 counts. If you have a 1762-OF4 and it's set to Raw/Proportional it would be looking for 6241-31206 counts. So if the input has 20 mA, you would get roughly 10.5 mA at the output.

 

[Saffa]

Chewing up one analog in and one analog out seems like an expensive way to re-transmit a signal if there's no need to manipulate it in any way. Have you considered using a 4-20mA loop isolator?

 

[forqnc]

Probably scaling. If you have a 1762-IF4 and it's set to for Scaled for PID it would give you 0-16383 counts. If you have a 1762-OF4 and it's set to Raw/Proportional it would be looking for 6241-31206 counts. So if the input has 20 mA, you would get roughly 10.5 mA at the output.

As Old No. 7 states, I would verify the I/O configuration for the Input and Output. I had a situation where the input was set for 4-20mA but the output was at 0-10Vdc.

 

[BrettL]

Chewing up one analog in and one analog out seems like an expensive way to re-transmit a signal if there's no need to manipulate it in any way. Have you considered using a 4-20mA loop isolator?

It is executing some logic and re-transmitting.

 

[BrettL]

Probably scaling. If you have a 1762-IF4 and it's set to for Scaled for PID it would give you 0-16383 counts. If you have a 1762-OF4 and it's set to Raw/Proportional it would be looking for 6241-31206 counts. So if the input has 20 mA, you would get roughly 10.5 mA at the output.

I think you nailed it. Thanks for the insight.