Question

When using the PID loops with my D2-250, my process variable doesn't look correct coming from my analog or temperature card. What's wrong?

Answer

The Setpoint Value (SP), Process Variable (PV), Bias (Integrator) and Control Output Value (CO) are in binary format. If you use the pointer method to bring the analog signals into the CPU be aware of the format you have specified. With the pointer method, if you do not precede the number of channels constant with an '8' the value is in BCD. You must do a BIN conversion before OUTing this value to Word+3 (PV). Also, make sure the proper format from the Word+5 (CO) is in the proper format when it reaches its module. It is in binary format when it leaves the PID loop. The loop table specifications are contained in the PID chapter of the User Manual.

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FAQ Subcategory: PID

This item was last updated on 2001-11-07
Document ID: 51

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