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3.2 Working principle
The Feltest AirSpeed/2 works with a vane or propeller anemometer as
the propeller has proofed to be more accurate and durable than a ther-
mal anemometer in the harsh environment of a paper machine.
The propeller speed, directly corresponding to the flow rate, is sensed
electronically without inducing any reaction force and is transmitted to
the read out unit.
The read-out unit operates through a microprocessor with a minimum
current loading. This makes it possible to perform all functions and
measurements by using only a few keys and allows the data to be cal-
led up at any time. The measuring data are read on the LCD display.
The unit is battery operated.
4. The measurement
It is of utmost importance to work safely when
measuring the air speed through a press felt. Find
a safe and stable position close to the Uhle box,
expand the telescopic grip so it will not be
necessary to bend over into the machine but most
important is to
stay away from any in-going nip!
4.1 Measuring procedure
Preparation
The connector and cable of the probe are led through the telescopic
grip. Then the measuring head and the telescopic grip can be mounted
together. The connector is clicked into the read out unit (watch the red
dots) and the instrument can be switched on with the On/Off key.
The instrument performs a functional test lasting about 2 seconds.
During this time the display shows the probe code 15.20. The first 2
digits indicate the propeller head diameter, the last 2 digits the full-
scale reading in m/s.
The instrument now measures continuously and shows the average
value of the last 2 seconds on the display. The display is refreshed
every 0,5 second. Changeover to 6 or 22 seconds average: press the
7
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