# 9. Performing a Pole-Zero Analysis

You can use the LabVIEW System Identification Assistant to compute the poles and zeros of the transfer function for one input-output pair of a model. The Pole-Zero Analysis step computes the pole-zero plot for a model.

Complete the following steps to perform a pole-zero analysis of the ARX model.

- In the Project View, right-click the
**Parametric Estimation**step and select**Insert After»System Identification»Model Analysis»Pole-Zero Analysis**from the shortcut menu to add a Pole-Zero Analysis step after the Parametric Estimation step. - On the
**Input Model**tab in the Configuration View, verify that**ARX Model**is selected in the**Model**pull-down menu.**ARX Model**is the only model output from previous steps and therefore appears by default in this menu. - The
**Pole-Zero Plot**displays the poles and zeros of the ARX model. Notice that all the poles of the plot are inside the unit circle, which indicates that the system is stable. A stable system reaches a steady-state value.

Also notice that the poles are on the real axis, which illustrates the monotonic nature of the signal. Poles with imaginary components indicate an oscillating signal. - You can set the minimum and maximum values of the x- and y-scales of the plot to resize the plot. Click the maximum value on the x-axis and change the value to 3. Notice the zero on the
**Pole-Zero Plot**, as shown in the following figure.

- Select
**File»Save Project**to save the project.

Previous: 8. Viewing Model Information | Next: 10. Validating the ARX Model |