Mitsubishi FX2N PID (FNC 88)

I was wondering if anyone knows mush about the PID loop in the FX2N PLC. I am using the PID loop to control a heat exchanger. I can't seem to get the PID to automaticlly update the variable for the burner control. I can control the burner output by loading the data manually using a compare statement and loading a high and a low value into the min and max limits. How do I read the values from the PID loop to control the burner output. Using an FX2n-4DA Analog output module for the burner control.


Thanks,
Kari Swimelar

Hi, when you called the PID function you parameterised it with a set of values, one of these is the start of the PID block data memory area.
i.e D500, if you check the documentation (downloadable from Mitsubishi) you will see that some of them are used internally, some read some write, one of these will be the manipulated output to control say a propotional valve via an analog output.
Not quite sure which data memory offset this is but for example if D500 was the start of the PID parameters block then if in the documentation Dn+22 is the manipulated output then D522 would contain the -32767 to +32767 value (this varies dependant on other settings forced into some of the data memory areas from D500>).
use this Data memory (might need some re-scaling)& transfer this to the analog output using the TO function.
If I have time I will look at the one I did some time ago & post it.
Hope this helps, Parky.

With Mitsu's PID I must advise you to read CAREFULLY there in-house definition of ALL the variables. You will be amazed on what they do compare to what is generally accepted as the definition.

Poeple who have dealt with there idea of sink and source are aware that they have there own dictionnairy.

Read again.