# Simple PID explanation

## 8 posts in this topic

I am using Cx-programmer version 9.4 and i was wondering if anyone could clarify how to use the PIDAT (191). Been searching online but im not really sure how to work it. im not sure how to implement all the parameters needed to use this function so if anyone can help me out that would be awesome. :helpme:

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First try reading manual!! Then come back with your questions! Note that PIDAT is the same as PID with the added Auto Tuning capability.

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Bits N Bytes is correct.... RTFM first.... and i think there is a PIDAT FB in the download section. as for the selection of the P I and D parameters and the T constant.. well i suggest getting an understanding of PID first... the one thing that Omron is a little different is that P is Proportional Band - in other PLCs P is Gain... the Proportional Band is the Inverse of Proportional Gain ie PB = 100/PG and PG=100/PB google PID and there is a wealth of info... if you are stuck at trying to determine a base P I D value then look at a Omron temp controller and look at the default settings for P I and D....

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i cannot find the "PIDAT" function block example in the download section.

thanks.

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Chou, there was issues with a recent site update.  I have added it back to the post for you.

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Dear Michael,

May i know why the PID is not function when i set the SETPOINT value to negative ? (let say -55)

thanks.

Chou

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Sorry arsenen8, I just saw this post.  Somehow I missed it.  The function block is designed to work with a positive feedback value (an analog input for instance) and is therefore looking for positive numbers.  If you treat -55 as an unsigned integer, it is 65481.  This number is likely larger than the number of bits that you have selected for your feedback, so it stops working.  As a fix to your issue, you could always apply an offset to your input and to your setpoint to compensate.  For instance, if your values range from -500 to 500, then you could add 500 to your feedback and then set your setpoint from 0 to 1000.

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I want sample ladder for PID CX ONE PROGRAM