Graphical Programming with LabVIEW

Circuit Analysis III

The Equations

In this exercise we make a graphical program with LabVIEW using a set of four equations I provide below. These equations solve the particular circuit shown below, in which there are seven inputs: V (the battery voltage); and R1 through R6 (six resistances); and four outputs: I (the total current); V2; V4; and V6 (voltages across corresponding resistances as shown in figure):

(1)

(2)

(3)

(4)

The Program

(1) Enter the inputs and outputs into the Front Panel; use appropriate labels (Right Click and Show-Label if needed)

(2) Enter operators into the Block Diagram in such a way that minimal wiring will be required. Start with equation (1) and R5+R6 (try to see why!). Use minimum amount of wires, the resulting diagram should look like or better than the example shown below.

(3) Once all elements are entered and the Run button (arrow) is not broken (this means no “grammar” errors), prepare some simple numbers to check the results against. For example, if you plug: V=9V; R1 through R6=1 Ohm into the above equations, using a calculator you will obtain: I=5.54A; V2=3.46V; V4=1.38V; V6=0.69V.

(4) Before you can say “I’ve made a program”, it should be validated, i.e. set the inputs in the Front Panel to V=9V; R1 through R6=1 Ohm, and run the program to see whether the correct results are obtained. If not, the program needs to be checked and corrected. The validation process is not finished until the correct results are achieved!