Young Ultrasonic Anemometer Voltage and Serial Output Model 81000 - Manual (Page 7)

Page 6
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needed and, when operated in polled mode, the connections may
be bussed.
Long custom output strings at high output rates and low baud rates
may exceed the time needed to send the string. Solutions include
using fewer measurement parameters, lower OUTPUT RATES,
higher BAUD RATE, or some combination of these solutions. With
measurement parameters, for example, sending wind data in both
UVW and SPEED, AZIMUTH, ELEVATION formats is redundant
and wastes space in the string.
HALF DUPLEX TIMING CONSTRAINTS
If RS-485 half-duplex mode is used for continuous output, high
output rates and long output strings create a progressively smaller
window of time in which to receive commands. Under some
conditions, the 81000 may not respond to the ESC commands
since the unit will be spending most of its time in transmit mode.
RS-485 is best used in POLLED MODE or at modest output rates.
In contrast, a full-duplex RS-232 or RS-485 scheme is immune
to the timing limitations described above and commands may be
received even while data is being sent.
Polling in half-duplex RS-485 mode at high rates may be limited
by the timing capability of both the polling device and the 81000.
Advantages gained from bussing multiple sensors may be lost
if timing problems arise. For fast polling, a full-duplex scheme is
recommended.
HIGH WIND SPEED MEASUREMENTS
For best measurement results, particularly at high wind speeds,
always choose the lowest OUTPUT RATE possible. Lower output
rates use a greater number of internal samples to generate the
result and are more immune to outliers in the samples. If measur-
ing for spectral content, carefully determine the needed sampling
rate and use the lowest OUTPUT RATE necessary.
RAIN AND SNOW
Anything that blocks the acoustic signal path will degrade the mea-
surement. If the path is blocked suf ciently, measurements cannot
be made. The 81000 can make accurate measurements in driving
rain even at high OUTPUT RATES but light mist or heavy fog can
allow droplets to accumulate on the transducer faces and block the
measurement.
Measurements may be made in driving snow although frost and
snow that adheres to the transducer face may block the measure-
ment. Similarly, freezing rain on the transducer face may block the
measurement.
POWER CONNECTIONS
Supply power must be in the range of 12 to 24 VDC at the sensor
junction box terminals in order for the sensor to operate properly.
For long cables, be sure to allow for voltage drop due to wire
resistance.
8.0 WARRANTY
This product is warranted to be free of defects in materials and
construction for a period of 12 months from date of initial purchase.
Liability is limited to repair or replacement of defective item. A copy
of the warranty policy may be obtained from R. M. Young Com-
pany.
9.0 CE COMPLIANCE
This product has been tested and shown to comply with European
CE requirements for the EMC Directive. Note that shielded cable
must be used.
Declaration of Conformity
R. M. Young Company
2801 Aero Park Drive
Traverse City, MI 49686 USA
Model 81000 Ultrasonic Anemometer
The undersigned hereby declares, on behalf of R. M.
Young Company that the above-referenced product, to
which this declaration relates, is in conformity with the
provisions of:
Council Directive 2004/108/EC (December 15, 2004)
on Electromagnetic Compatibility
David Poinsett
R&D Manager