Young Gill Propeller Anemometer Models 27106 - Manual (Page 2)

Page 1
27106-90(E)
INTRODUCTION
The Gill Propeller Anemometer is a low threshold precision air velocity
sensor employing a fast response helicoid propeller. The instrument
uses a high quality tech-generator transducer which converts propeller
rotation to a DC voltage that is linearly proportional to air velocity. The
output signal is suitable for a wide range of signal translators and data
logging devices.
Airfl ow from any direction may be measured, however, the propeller
responds only to the component of the air fl ow which is parallel to the
axis of its rotation. Off-axis response closely approximates a cosine
curve (see accompanying graphs) with appropriate polarity. With
perpendicular air fl ow, the propeller does not rotate.
For detailed studies of low air speeds, optional propeller shaft
extensions improve response in the 90° stall region by improving
symmetry and reducing the stall angle.
The instrument mounts to 3/4 inch standard pipe. A rugged cable
connector provides both electrical and mechanical connection. A
dustcap is provided to protect the connector when the instrument is
removed.
INITIAL CHECKOUT
When the instrument is unpacked it should be carefully checked for
any signs of shipping damage. The propeller shaft should rotate easily
without friction.
Using the WIRING DIAGRAM as a guide, connect the instrument to
an indicator or voltmeter and check for proper signals from the sensor.
The calibration may be checked using the methods outlined in the
CALIBRATION section of this manual.
INSTALLATION
Generally, the instrument should be oriented with the propeller
facing the predominant fl ow of air being measured. In some cases
it is appropriate to orient the instrument so the predominant air fl ow
is perpendicular to the propeller such as in applications measuring
the vertical component of wind. Keep in mind that off-axis response
increases the effective threshold and distance constant.
For vertical measurements mount the instrument so the propeller faces
upward. This helps prevent moisture or dirt from entering around the
propeller hub and potentially contaminating the bearings.
If the instrument is used to measure high air velocity or left for extended
periods without attention, tape the threaded cable connector collar to
eliminate the possibility of loosening from vibration. The threaded joint
between the generator and shaft housings may also be taped.
For some applications commutator ripple from the tech-generator may
need to be reduced. Use a 500 uF 10 VDC non-polarized capacitor
connected across the sensor leads as shown in the wiring diagram.
Given the low internal resistance of the tech-generator the effective
time constant of this fi lter is approximately 15 mS and will not degrade
measurement accuracy to any signifi cant degree.
The instrument measures both forward and reverse air fl ow. Signal
polarity relative to the connection pins is shown in the wiring diagram.
In applications measuring horizontal air fl ow, most users connect
the sensor to produce a positive signal with fl ow from the front
(counterclockwise propeller rotation). In applications measuring vertical
air fl ow, the sensor is usually connected so downdrafts produce a
negative signal, updrafts a positive signal.
Output from the tech-generator should be connected to a load
impedance of 10k ohms or higher.
SPECIFICATION SUMMARY
Range, Axial Flow 0-30 m/s (70 mph)
Range, All Angles 0-25 m/s (55 mph)
Propeller 22 cm diameter 4-blade helicoid propeller,
expanded polystyrene
Pitch 29.4 cm air passage per revolution
Distance Constant* 1.0 m (3.2 ft.)
Threshold Sensitivity* 0.3 m/s (0.6 mph)
Signal Output Analog DC voltage proportional to axial wind
component. Polarity reverses with reverse
rotation.
1800 rpm (500 mV) = 8.8 m/s (19.7 mph).
Power Requirement Anemometer is self powered.
Specifi cations represent nominal values determined in accordance with
ASTM standard procedures.
* Threshold and Distance Constant values are for axial fl ow.
GENERAL
Operating Temperature: -50 to 50°C (-58 to 122°F)
MODEL 27106
GILL PROPELLER
ANEMOMETER