Complete the following steps to build a VI that measures
temperature every 0.25 seconds for 10 seconds. During the
acquisition, the VI displays the measurements in real time on a
waveform chart. After the acquisition is complete,
the VI plots the data on a graph and calculates the minimum,
maximum, and average temperatures. The VI displays the best fit
of the temperature graph.
- Open a blank VI and build the front panel shown in
Figure 1.
-
Set the point style of the
waveform chart plot to a
small xx.
-
Hide the plot legend of the
waveform chart.
-
Change the label of the
waveform chart to
Temperature Chart.
-
Change the label of the
waveform graph to
Temperature Graph.
-
Right-click
Temperature Chart and select
Properties from the shortcut menu. On the
Scales tab, change the x-axis multiplier to
0.25. On the Format and
Precision tab, change the Digits of
Precision to 2. The
data for Temperature Graph will be
formatted on the block diagram.
-
Resize the plot legend of the
waveform
graph to show two plots.
-
Change the name of
Plot 0 to
Temp and Plot 1 to
Fitted.
-
Set the point style of the
waveform graph
Temp plot to a small square.
-
Do not create the
Mean, Max,
andMinindicators yet. They will be created
from the block diagram.
-
Build the block diagram Figure 2.
-
Place the Thermometer VI on the block
diagram. Select Functions>>All Functions>>Select a
VI and navigate to C:\Exercises\LabVIEW
Basics I\Thermometer.vi. This subVI returns one
point of temperature data.
-
Place the Wait Until Next ms Multiple
function, located on the Functions>>All
Functions>>Time & Dialog palette, on the
block diagram. This function causes the For
Loop to execute every
0.25seconds
0.25
seconds
(
250ms
250
ms
).
-
Place the Array Max & Min function,
located on the Functions>>All
Functions>>Array palette, on the block
diagram. This function returns the maximum and minimum
temperature.
-
Place the Mean VI, located on the
Functions>>All
Functions>>Analyze>>Mathematics>>Probability and
Statistics palette, on the block diagram. This
subVI returns the average of the temperature
measurements.
-
Right-click the output terminals of the
Array Max
& Min function and Mean VI and
select Create>>Indicator from the
shortcut menu to create the Max,
Min, and Mean indicators.
-
Place the General Polynomial Fit VI,
located on the Functions>>All
Functions>>Analyze>>Mathematics>>Curve Fitting
palette, on the block diagram. This subVI returns an
array that is a polynomial fit to the temperature array.
-
Place the Bundle function, located on the
Functions>>All Functions>>Cluster palette,
on the block diagram. This function assembles the plot
elements into a single cluster. Press the
<Ctrl> key while you drag the function
to copy it. The elements include the initial
xx value (0),
the
Δx
Δ
x
value (0.25), and the
yy array of temperature
data. The
Δx
Δ
x
value of 0.25 is required so that
the VI plots the temperature array points every
0.250.25 seconds on the
waveform graph.
-
Place the Build Array function, located on
the Functions>>All Functions>>Array
palette, on the block diagram. This function creates an
array of clusters from the temperature cluster and the
best fit cluster.
-
Complete the block diagram as shown.
-
Save the VI as
Temperature Analysis.vi in the
C:\Exercises\LabVIEW Basics I directory.
-
Display the front panel and run the VI.
The graph displays both the temperature data and best fit
curve of the temperature waveform.
-
Try different values for the polynomial order constant on
the block diagram and run the VI again.
-
Change the appearance of the plots by modifying the plot
styles and fill styles.
-
Right-click the
Temp plot display in the
plot legend and select Common Plots>>Scatter
Plot from the shortcut menu, the top middle
option.
-
Right-click the
Fitted plot display in the
plot legend, select Bar Plots from the
shortcut menu, and select the second option in the
middle row. The waveform graph should
appear similar to the front panel in Figure 3.
- Save and close the VI.
"A full introductory course on programming with LabVIEW."