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How to integrate a variable between 2 instants on the fly with the post-processing tool?

Community Manager Community Manager
Community Manager

Question:

How to integrate a variable between 2 instants on the fly with the post-processing tool?

Answer:

For instance if we have a flowrate chart Q=f(t) and we want to know the corresponding volume between instants t1 and t2.

We can use the "integ" post-processing function and can combine it with the "restrict" function to limit this integration between t1 and t2.

The expression would then be: integ(restrict(flowrate_variable,t1,t2))

In order to get the actual flow value at t2 you would use: valueat(integ(restrict(flowrate_variable,t1,t2)),t2)

Then, it is important to notice that variables referenced in post processing expressions always have a default unit, so we may need to convert to the unit of interest. In our example, the flowrate is in L/min but the integration is done over a time in seconds.

An easy way is to change the unit of the variable from L/min to L/s and then drag it into the post-processing view to get the correct conversion factor.

amesim_unit_post_processing.jpg

 

Did you know that post-processing allows many more calculations?

For example you could also get the maximum of a signal during a specific time range, get the time at which the maximum is reached, filter signals and compute derivatives, averages… Parameters of the model can also be referenced. Here's an extract of the available functions:

Post_Processing_Forum_LMS_Amesim.png