HMI Analog Output

Hi,

Here I attached the zip program to understand the problem and get the solution too, 

Shahadat96

Hi,

Here I attached the zip program to understand the problem and get the solution too, 

The analog %IW96 is going to a small negative value.
You can view FB10 network 8 to confirm. 

Figure 1. FB10.8: Location of analog reading that is negative at rest.

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There is noise on the analog reading which may be because of insufficient shielding or bad grounding. The signal ground of the analog card may not be the same reference as the current transducer. A fluctuating rest value points to an unconnected signal reference. The best engineering solution is to find out why the analog is going negative.

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One solution patch is to use the NORM_X instruction where the minimum value for the analog input is not at 0, but at the actual rest value. That means a calibration is doen for the analog input. Put that also means it needs to be done for all analog inputs. 

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Another patch idea is to make changes to FB6 to ignore negative values. The recommended changes are shown in the next figure. This idea is the quickest to implement but it only hides the actual problem. But the real issue may be insignificant if the negative reading does not fluctuate and stays small.


Figure 2. Suggested changes to FB6 to ensure engineering values are within limits.