Table of Contents
Advertisement
7.0 APPLICATION NOTES
SERIAL COMMUNICATION
Selection of RS-232 or RS-485 is made inside the sensor J-box
by positioning the shorting blocks on jumper W6. Typical wiring
connections are shown in APPENDIX A.
connections can simplify some installations since less cable is
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 measuring 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
measurement. If the path is blocked sufficiently, 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 measurement.
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.
VOLTAGE INPUTS
The voltage inputs have no anti‑aliasing filters. This has no impact
on low frequency or D.C. measurements. Users wishing to examine
spectral components of voltage input measurements may need to
supply an external anti‑aliasing filter if the signal contains meaningful
energy above the OUTPUT RATE frequency (f).
8.0 EMC COMPLIANCE
This sensor complies with limits for a Class A digital device, pursuant
to part 15 of the FCC Rules, and IEC standard 61326-1. This sensor
generates, uses, and can radiate radio frequency energy and, if
not installed and used in accordance with the instruction manual,
RS-485 half-duplex
may cause harmful interference to radio communications. Sensor
operation may be temporarily affected by radio frequency and
transient interference sources, but will revert to proper operation
when the source of interference is removed.
9.0 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 the defective item. A copy
of the warranty policy may be obtained from R. M. Young Company.
Page 5
81000V-90(L)
Advertisement
Table of Contents
