United Sensor Corporation has two wind tunnels available for which to perform probe
calibrations.
Since each of United Sensor's probes is hand made, there
may be inherent pressure measurement
differences due to machining and assembly
tolerances. It is important to be able to calibrate the
pressure
readings of any given probe against a standard probe.
Both of United Sensor's wind tunnels consists of a flow straightening section, a
measurement
section, and a fan downstream of the measurement section.
Since the fan is located downstream of
the measurement section, the flow
is produced by a vacuum downstream of the probe. Because of
this,
a probe in the flow stream will have a nearly constant total pressure reading
while the static
pressure reading decreases as the flow speed is increased.
The primary wind tunnel used at United Sensor Corporation for calibrations is octagonal
shaped
and has an 8 inch cross section. It is possible to achieve
velocity pressures of about 21 cm of
water. The secondary
wind tunnel has a square crossection and is 2.75 inches wide. It is possible
to achieve velocity pressure of up to 30 cm of water in the smaller
section tunnel. Typical
calibrations are performed at 20 cm of water.
United Sensor recommends that a probe be calibrated
at a flow
speed that is similar to that which the probe is to be used.
Probes can be calibrated with both pitch and yaw angle set to zero with respect to
the flow or can
be calibrated by varying the pitch angle while the yaw
angle is zero or by varying the yaw angle
while the pitch angle is constant.
If a calibration is performed with the larger wind tunnel, it is
possible to achieve pitch angles of +/- 50 degrees in 5 degree increments, whereas
it is only
possible to achieve +/- 40 degrees in 10 degree increments
in the smaller tunnel. With both tunnels,
it is possible to achieve
any angle in yaw with an uncertainty of about half a degree. Typical
calibrations that are included with many of United Sensor's three dimensional and two dimensional
probes consist of a pitch calibration with angles of +/- 40, 30, 20, 10 and 0 degrees
while the yaw is
set to zero.
Standard prices for calibrations services:
| Set-up charge
per probe: |
$148.00 |
| Each
calibration
point: |
$39.00 |
Additional
charges
may
be
required
if
the probe requires special mounting in the wind tunnel.
Contact
United Sensor Corporation for details.
