Section 2 Functional Description
13 FT722 & FT742 (RS485) – FF & PM Sensors – User Manual
Since the heater circuit is thermostatically controlled, the actual power being drawn from the supply will depend
on the programmed set-point and the environmental conditions (i.e. ambient temperature, wind speed,
precipitation etc.). The maximum power that the sensor can consume is by default software limited to 99W (with
the heater enabled). The power supply must be rated to provide the maximum power that the sensor can consume.
The maximum current limit of the sensor can be adjusted between 0.1 and 6.0 Amps (from the default of 4 Amps
and in increments of 100mA). By default the heater requires a minimum of 11VDC for operation. The heater
activation voltage and the maximum current limit can be changed at the factory, using the Acu-Vis test software
or the HTL software command (see Section 6.4.17).
If the sensor is powered up and there is a possibility it has become iced, it is recommended that the sensor is
allowed to heat up for 30 minutes, followed by a User Reset Command (see Section 6.4.21) to permit the sensor
to initialise correctly without ice blockage.
2.9 Acoustic Temperature
The Acoustic Temperature feature takes a measurement of the ambient temperature via measurable acoustic
properties of the airflow. Sections 6.4.2, 6.4.3 and 6.4.4 describe related software commands.
The averaging system can be performed for 0 to 50 seconds (in increments of 10 seconds), or between 1 to 10
minutes (in increments of 1 minute).
See Section 2.1 for details regarding operating specifications. Operation with high temperature gradients
(between sensor body and ambient airflow), extreme humidity levels and low wind conditions (below 5m/s) may
result in reduced accuracy.
Caution: The acoustic temperature feature requires calibration at FT Technologies. If the sensor has had a
software upgrade to 7.5 (or above) then the data will be uncalibrated and may not comply with the official
specification. Testing is recommended to confirm suitability for the application.
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