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10. USING THE ANALOGUE OUTPUTS
10.1 Introduction
Analogue outputs can be provided by an additional analogue output card mounted inside the power
supply and communications unit (PCI). PCIs with this card fitted have a model number 1189PCA.
PCIs without analogue outputs have a model number 1189PC.
The analogue output card decodes the serial message from the anemometer and generates the
appropriate analogue outputs. Seven analogue outputs are provided of 14 bit resolution. The pin
assignment and electrical specification for these is given in Section 13.
10.2 Analogue outputs
Channels 1,2 and 3 - Wind velocity
These channels represent the wind velocity. The variables represented by each channel depend on
the anemometer's operating mode, and are defined in the following table:
Output Channel
Mode 1 2 3
UVW
U V W
Polar format
Dir. Mag. W
Axis velocities
Axis 1 Axis 2 Axis 3
For U, V and W magnitude, and axis velocities, ±2.5V represents ±10, ±20, ±30 or
±60m/s as selected when configuring the anemometer. For direction in polar format the ±2.5V
output range represents either 360° or 540°. This option is also set up when configuring the
anemometer, either using the supplied RCOM software or using the anemometer's interactive mode
commands.
The direction representation is:
Output voltage (V)
-
2.5 -0.833 0 +0.833 +2.5
360°
-180° 0° +180°
540°
0° 180° 360° +540°
The 540° mode avoids the output oscillating between -2.5V and +2.5V in response to a direction
varying around 180°.
Channel 4
- Speed of Sound or Sonic Temperature
The variable represented by this analogue output also depends on the configuration of the
anemometer's speed of sound or sonic temperature. The representations for each available mode are:
Output voltage (V)
-2.5 -1.667 0 +2.5
Speed of Sound
300 311.667 335 370
Sonic temperature (Kelvin)
233.15 273.15 333.15
Sonic temperature (Celsius)
-40 0 +60
Channel 5 - Absolute Temperature
The voltage output at a given temperature is independent of the anemometer's temperature output
configuration. The following table shows the mapping between voltage and temperature:
Output voltage (V)
-1.667 0 +2.5
HS-50 Research Anemometer Page 35 Issue 02
Doc. No. 1199-PS-0032 November 2004