use of auxilary inputs

how can i write design a ladder to check the flow through pump is going or not, using auxiliary inputs?

How are you going to detect flow through the pump with aux inputs? The only thing I can think of that the aux input will detect is that the pump motor itself is running, regardless of the flow through it...

OZEE said:

How are you going to detect flow through the pump with aux inputs? The only thing I can think of that the aux input will detect is that the pump motor itself is running, regardless of the flow through it...

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It really does not even tell you that, it just says the motor starter's contactor has pull-in.
A flow switch is the best option, or maybe a pressure switch depending on the process. But if there is a valve closed pressure does not work either.

I think you are running the pump to satisfy a need in other equipment. That is what I would sense for example temperature of water going in and of water going out.

Dan Bentler

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in pump if i use hard contacts to monitor the status it will load the pump.
that's why to use auxiliary contacts,
10 liter water is to be dispatched from tank within 10 minutes.
if in case of blockage fluid passes only for 6 minutes.
i want to stop the pump so that i can save remaining 4 minutes flow.
cause if not 10 liters in 10 minute them mixture in reactor should drain out.

OK, it sounds like you're wanting to monitor flow, not the status of the aux contact.