Hi,
I just need an information about der() operator. I receive two signals as outputs of a C external function.
Then I've to put them in a system of equation.
If I write

Real vx(start=12);      

Real del(start=0);    

  

Real psi;    

Real phi;    



equation 



(del,vx)=ExternalFunc1(val); 

  phi=del*vx/10000000; 

  vx=psi/cpitch; 

it works properly.

But if I insert a der operator on the acquired variable.

Real vx;      

Real del;    

  

Real psi;    

Real phi;    



equation 



(del,vx)=ExternalFunc1(val); 

  phi=del*vx/10000000; 

  der(vx)=psi/cpitch;

it gives me the following error:

resultFile = "Simulation failed.
Error: Model is structurally singular, error found sorting equations Algorithm no: 0 for inputs: () => outputs: (vx, del);
Algorithm no: 0 for inputs: () => outputs: (vx, del);
for variables del(3)

I tried also adding an initial equation but the result is the same. I think I'm making some mistake but I can't find it.
Can you help me please?

Regards,
Francesco