Vaisala WS425FG - Manual (Page 58)

User's Guide ______________________________________________________________________
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response can be calibrated to a known ambient temperature with the
WSTK command below.
The output is of a fixed character length with 5 characters for the static
speed of sound and 6 characters for the sonic temperature. Positive
temperatures at or under 99.9° F will be padded with a leading zero.
This leading zero will be replaced by a minus sign for negative
temperatures.
An example of the response:
670.5 023.0
If the sensor is unable to compute the values due to a problem with the
sensor, the missing data response will be the following:
999.9 099.9
WSTK Command
This command is used to calibrate the static speed of sound and sonic
temperature. The command format is:
WSTK CR LF
The command allows the static speed of sound and sonic temperature
output products to be refined by calibration to the known ambient
temperature. This calibration command does not impact the measured
wind speed and direction accuracy in any way.
The calibration function should be done indoors in a controlled
environment. The ambient temperature input to the sensor during the
calibration operation must be an accurate measurement of the air
temperature at the sensor position at time of input. There should be little
if any ambient airflow. Typical airflow from building HVAC will not
unduly disturb the reading as long as the sensor is not directly next to or
under a register. The zero wind verifier and/or bag must not be placed
on the sensor during this calibration function. The resulting calibration
constant will be stored in the non-volatile memory and will survive
future firmware downloads as long as it is still relevant to the new
firmware.
NOTE Do not place the zero wind verifier and/or bag on the sensor during
calibration.