56
SERVICE
•
Wind Direction: The ATMOS 41W wind direction measurement depends on the geometry
of the ultrasonic transducers and the north orientation indicator on the ATMOS 41W body.
This geometry is held to within 0.025-mm specifications through CNC milling procedures.
Imprecise orientation of the ATMOS 41W toward north will introduce more error in the wind
direction measurement than sensor geometry.
•
Sensor Orientation: The ATMOS 41W orientation sensor is zeroed against the primary
bubble level on the bottom side of the upper anemometer housing.
5.3 RECALIBRATION RECOMMENDATIONS
Table 6
lists the recommended sensor calibration frequencies.
Table 6 Sensor calibration frequencies
Sensor Function
Measurement Drift
Calibration Frequency
Solar radiation
<2% drift/year
Every 2 years
a
Barometric pressure
0.1 kPa/year (typical)
Every 1–2 years
b
Relative humidity (RH)
<0.25% RH/year
Every 2 years
b
All other sensors
Not needed
a
Calibrated, field-swappable replacement pyranometers are available from METER. Contact
purchase a new funnel and consult
Instructions for Swapping ATMOS 41W Funnel
(meter.ly/41W-funnel-replace)
for instructions on field swapping the pyranometer.
b
ATMOS 41W barometric pressure and vapor pressure/RH sensors and their respective calibrations are housed on
a module that sits behind the circular Teflon membrane in the same housing as the sonic transducers (
Figure 19
).
This module is field-swappable, so sensors in need of calibration can be removed and replaced by a module with
calibrated sensors. Please contact
for new sensor modules and consult
VIDEO: Instructions for
swapping ATMOS 41 daughterboard—RH/temperature/barometric pressure sensors
(meter.ly/atmos41-swap-RH-
daughterboard) for instructions on swapping the sensor module.
5.4 CLEANING AND MAINTENANCE
For more information on thoroughly cleaning the ATMOS 41W, see
ATMOS 41W cleaning
instructions
(https://meter.ly/atmos-cleaning-instructions).
1. Make sure nothing is obscuring the temperature sensor or the sonic transducers shown
in
Figure 30
(cobwebs, leaves, wasp nests, etc.).
