R.M. Young 27106T, Quick Start Manual

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27106T-90

MODEL 27106T

GILL PROPELLER
ANEMOMETER

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.

Airflow from any direction may be measured, however, the
propeller responds only to the component of the air flow 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 flow, 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 flow of air being measured. In some
cases it is appropriate to orient the instrument so the
predominant air flow 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 filter is
approximately 15 mS and will not degrade measurement
accuracy to any significant degree.

The instrument measures both forward and reverse air flow.
Signal polarity relative to the connection pins is shown in the
wiring diagram. In applications measuring horizontal air flow,
most users connect the sensor to produce a positive signal

SPECIFICATION SUMMARY

Range, Axial Flow

0-40 m/s (90 mph)

Range, All Angles

0-35 m/s (80 mph)

Propeller

20 cm diameter 4-blade helicoid propeller
molded of carbon fiber thermoplastic

Pitch

30.0 cm air passage per revolution

Distance Constant*

2.1 m (6.9 ft.)

Threshold Sensitivity*

0.4 m/s (0.8 mph)

Signal Output

Analog DC voltage proportional to axial
wind component.  Polarity reverses with
reverse rotation.
1800 rpm (500 mV) = 9.0 m/s (20.1 mph).

Power Requirement

Anemometer is self powered.

Specifications represent nominal values determined in
accordance with ASTM standard procedures.

*

Threshold and Distance Constant values are for axial flow.

GENERAL

Operating Temperature: -50 to 50°C (-58 to 122°F)