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Objective
The objective of this lab is to calibrate an electronic pressure transducer using LabVIEW and determine its accuracy
after calibration. The useful working range of the instrument is also important to know.

Equipment
DAQ and LabVIEW Pressure tester with analog pressure gauge
12 V DC power supply and electronic pressure transducer attached.

Procedure
Part 1 – Setup
1. Connect the DAQ to the USB port of the computer and open a blank VI in LabVIEW.
2. Connect the pressure transducer to the DC power supply (do not turn on until completely set up).
Red wire + terminal of DC power supply
Black wire – terminal of power supply
Green wire ground (this is the case grounding for the pressure tester)
Bare wire ground (this is the cable shielding of the wires from the pressure tester)
3. Connect the pressure transducer to the DAQ analog ports (this will involve some ingenuity at the DAQ).
White wire connect to a + port on the DAQ
Black wire connect to a – terminal of DC power supply AND to a – port on the DAQ

Part 2 – Build the VI (I’m not giving you a figure showing you the VI this week…)
4. On the Block, insert a DAQ assistant.
5. Select Acquire Signal ≫ Analog ≫ Voltage, and then select the ports you have used.
6. Set the DAQ to take 100 samples at 100 Hz.
7. Insert a statistics assistant to take the arithmetic mean of the 100 samples.
8. Display the result in a numerical indicator on the Front Panel. Label it Voltage Output.
9. You may want to try building an Event Structure with an OK button so that you can record data to a file.
Part 3 – Calibration
10. Create a table as shown below
P on analog gauge
(± PSI)
V output in LabVIEW (V)
Trial 1 Trial 2 Trial 3
0 … … …
20 .. … …
11. Turn on the DC power supply and set the voltage to 12 V.
12. Zero the analog pressure gauge by twisting the handle of the pressure tester.
13. Take one voltage measurement using the VI at each of 0, 20, 40, 60, 80 and 100 PSI.
Record the scale uncertainty in the pressure measurements on the analog pressure gauge.
Do not worry about uncertainties in the voltages…LabVIEW reads more sig figs than is reasonable!
14. Return the pressure to zero. Repeat steps 12 and 13 twice more.
DO NOT just take 3 measurements at each pressure in one go…that defeats the purpose!
15. Input the data to Excel (pressure and three columns of voltage measurements)
16. Take the average of the voltages for each pressure.
17. Plot pressure versus voltage as shown below.
18. Fit a linear regression line and display the equation.
This will be our calibration curve, telling us what pressure corresponds to a given output voltage

Part 4 – Modify VI to convert voltages into pressures
19. Insert a Formula box in your Block to convert the voltage output to pressure using the equation from the
regression line.
20. Display the result of the conversion in a numerical indicator on the Front Panel. Label it Pressure.
21. As an appendix in your report, include a printout of your VI.
Part 5 – Measurement
22. Take one pressure measurement using the VI at each of 10, 30, 50, 70 and 90 PSI.
These results should appear in your lab report.
We are using pressures between the pressures used for calibration, as we should be certain that the VI
will be correct at pressures at which we calibrated. It is the pressures in between that we need to
ensure are reading correctly.
For the future:
You will perform pressure measurements in fluids lab, and again if you ever use the wind tunnel
(differential pressures are used to find flow speeds, as in Lesson 12)….so
Save the VI you have created somewhere you can access it in the future!
Calculations
Determine the magnitude of the error in each of the measurements from step 22 (not the percent

Deliverables
A lab report including (but not limited to):
o Cover page and table of contents
o Objectives
See the objectives I set for the lab…don’t make up your own!
o Nomenclature
o Theory
Not much required in this lab.
o Equipment
A list and a circuit diagram to show how equipment was used.
o Procedure
Only if you had to modify the procedure provided.
o Measurements
A table with the average voltages and the spread in these values (this represents the
sensitivity error, k, in our instrument).
You should also include the Excel plot with the calibration curve.
It must show the data points as well as the regression line.
o Calculations
Equation for the regression line (not really calculated, but not a measurement either…).
Any calculations you feel are necessary.
o Discussion (some suggestions only…not a complete list)
A comment on whether the pressure measurements made in step 22 fall within the
uncertainties of the analog pressure gauge (accuracy).
A comment on the precision you observed in the voltage measurements during
calibration (both due to the analog pressure gauge and the sensitivity error).
A comment on the precision of the line of best fit (linearity error).
What sources of error were there and how could the lab be improved?
o Conclusion
Your conclusion must address the Objective: give a short description of the
measurement instrument you have created, its useful working range and its accuracy
over this range.
o Appendices
LabVIEW VI.
You may also wish to include Excel spreadsheets or MATLAB codes for calculations etc.