Using Device & System Parameters as Variables

Oddly named, but quite useful, pressing the Parameter tab reveals a small spreadsheet-like grid which lists all the parts in the circuit available for scrutiny (actually, only those parts which allow value changes, such as resistors, capacitors, current and voltage sources, and inductors, but not ground). Thus, the part’s name is displayed in the left cell, while its value is displayed in the right cell.

Clicking on the value allows the user to edit the value by typing in a new value or using the slider at the top of the tab to control the value. By using this in conjunction with a running Simulation, you can see what effects changing a parts values will have to the function of the circuit immediately using either the Circuit Visualizations or Virtual Instruments.

v5pics/circuit_tab.png

In the picture above, you can see that the VP0 voltage source's dc value has been selected. The default value of 5, which is set in the device properties in the circuit, appears in the parameter modification area above the table.

Use the "All", "Some", "Few" (default) button to expand to shrink the list of displayed devices and properties. The "Few" button lists just the primitive devices and their values, such as a resistor's resistance, inductor's inductance, and so forth. The "Some" button will add more sources and their properties, and the "All" button lists every devices and parameter that is accessible in the program.

Once the simulation is running and the circuit is "Live" you can take advantage of the Parameters panel to modify device parameters in real time and see the immediate effects. You can change a device's property by entering the value directly in the text box then pressing the accept v5pics/accept.png button to use the value. Or you can just use the slider to adjust the value. The Recenter button has the effect of making the current value the center of the slider. This is handy when you hit the end of the slider's range and want to go further. In this case, clicking on the recenter button will make the slider's end value the new center which will then allow you to continue modifying the parameter.

If you select the All or Some listings, devices and their primitive models will be listed. When you select these parameters, you have the option of changing the model with one from the database. For instance, you can change the model of a diode by highlighting the diode and its model name in the table. Then in the modification area, the accept v5pics/accept.png button is replaced by a selection ellipse v5pics/ellipse.png. Clicking on the ellipse will bring up a dialog box that will allow you to select a new model from the database.

Please note that while the simulation is running, modification of device parameters by double clicking on the device itself is not allowed. You will receive a warning message telling you to use the Parameters panel instead.

Results of any changes due to the Parameters panel modifications are shown in a number of ways. If you have Circuit Visualization (or State Display) turned on, the changes are reflected directly on the circuit itself in the form of colored wires and shapes on the wires. If you have the option to display text value, then the results are displayed as text readouts on the schematic also.

Perhaps the best way to examine the changes from the Parameters panel is to use the Virtual Instruments, where you can examine various readings from specific nodes and devices. See the Instruments for more information on setup and use.