1. ME 391 Instrumentation Lab 10 Calibration of a Hot-Film Anemometer
April 16, 2002
Andrew Comstock
“I believe I performed 50% of this lab.”
Jeff Hustace

2. Abstract
Objective: Students used a flow nozzle and a Kiel probe to measure the volume flow rate and centerline velocity of air flowing in a “wind tunnel.” These measurements were performed for a range of blower speeds and were used to calibrate a hot-film anemometer.
Method: The blower was started and brought to full speed by setting the rheostat to The pressure was measured across the flow nozzle and the Kiel probe and the hot-film voltage was recorded. This was repeated for different rheostat settings.
Conclusions: This lab does not work because the experimental data does not appear between the region of slug and parabolic flow.

3. Table 1

4. Table 2

5. The slug flow and parabolic lines do not bracket the data.

7. Table 3 Uncertainty in Q = +/- 3.9*10-5 (m3/s)
Uncertainty in VCL = +/ (m/s)
Uncertainty in VHF = +/ (volts)
All values are one sigma.

8. King’s Equation is valid.

9. Questions
For the method in figure 2 VCF(.1) = and VCF(100) = 4282.
For the method in figure 3 VCF(.1) = 2.7 and VCF(100) = 16.3
For the low value we would use the method in figure 2 because this method is more accurate for low velocities since it is a 4th order quadratic. For a high value we would use the method in figure 3 because the method in figure 2 grows exponentially which makes it inaccurate for high values.
Natural convection affects low velocities much more. At high velocities it becomes insensitive to voltage changes.