Logix5000 PID: Integral Accumlator

Quick question about the PID instruction.

The Integral Accumlator word (DATA[0]) seems to stop accumlating after a while on large setpoint changes.

Is there a point at which this is supposed to stop integrating the error? I thought this was continuous over the entire process.

Thanks.

Depends on what is going on in your loop. If the output is at CV High Limit or CV Low Limit, then it is normal.

Having the integral stop when the output at the limits is typical.

If PID calculations put the output past the limit it doesn't help to have the integral calculate a value even farther past the limit.

If the integral term is allow to grow when the output is at the limit, the only thing that happens is that it will take longer for the integral term to 'wind down' once the feedback reaches setpoint.