Use of integrator in Simulink

Im trying to find the area under the graph (called it graph A) from simulink graph A looks something like this: <a><[IMG]http://img171.imageshack.us/img171/5214/83269046.th.png[/IMG][/URL]</a>> (Sry dunno how to show image. Graph A looks sthing like a normally distributed curve)

but when i use an integrator from simulink, the graph i obtained showed a negative valuefor the initial part. There is no negative value for graph A. So is there something wrong with my method?

[Tan Edwin]

Additional info: 1) Im using fixed step solver of time step 0.1

2) Graph A comes from a S-function block output based on inherited time

3) When i change the time for S-function from [-1 0] to [0.1 0] everything works fine. so why cant i use inherited time?

[Tan Edwin]

4) i want to use inherited time so that the output from the s-function appear as a continuous curve instead of a step shape graph

[Kaustubha Govind]

What happens when you set continuous sample time for your S-function: [0 0]

[James Allison]

In the Diagnostics>Data Validity pane of configuration parameters, try setting 'Underspecified initialization detection' to 'Simplified'.

Answer 1

[Vineet Kumar]

The Integrator block outputs the value of the integral of its input signal with respect to time.

The Integrator Limited block is identical to the Integrator block with the exception that the output of the block is limited based on the upper and lower saturation limits. See Limiting the Integral for details.

Simulink® treats the Integrator block as a dynamic system with one state.