shiftedbits
Member
- Controllogix L61 PLC
- 1756- IF8 Analog Input Card set at RP1 of 75ms
I need to Totalize flow from a Mass flowmeter. Analog 4-20ma output from the flowmeter is the only available option as Pulse input from this flowmeter would require a High speed counter to be added. Latter is not an option due to rack space. Mass Flow Totalizing is done anywhere from 1 min to 5 minutes for a given totalizing cycle. Flowrate max is around 2k Grams/min. Accuracy being the most important, and this is the most critical of all the rest of the logic in the PLC, I have placed the totalizing routine inside a 100msec periodic task. I am also scaling the analog input for this channel in this same periodic task before the totalizing rung.
My question is, is scaling the Analog input inside a "Periodic Task" bad practice?
What about using a 25msec periodic task? Overkill?
Analog Card's minimum RPI is 18ms so I assume setting the Periodic task below this value is not going to buy anything in terms of Accuracy. Am I correct in this assumption?
Thanks-
- 1756- IF8 Analog Input Card set at RP1 of 75ms
I need to Totalize flow from a Mass flowmeter. Analog 4-20ma output from the flowmeter is the only available option as Pulse input from this flowmeter would require a High speed counter to be added. Latter is not an option due to rack space. Mass Flow Totalizing is done anywhere from 1 min to 5 minutes for a given totalizing cycle. Flowrate max is around 2k Grams/min. Accuracy being the most important, and this is the most critical of all the rest of the logic in the PLC, I have placed the totalizing routine inside a 100msec periodic task. I am also scaling the analog input for this channel in this same periodic task before the totalizing rung.
My question is, is scaling the Analog input inside a "Periodic Task" bad practice?
What about using a 25msec periodic task? Overkill?
Analog Card's minimum RPI is 18ms so I assume setting the Periodic task below this value is not going to buy anything in terms of Accuracy. Am I correct in this assumption?
Thanks-