Operating Manual
ARS31(Pro)-UMB
G. Lufft Mess- und Regeltechnik GmbH, Fellbach, Germany
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Difference between the
“saline concentration” channels 801, 803, 805, 816, 817, 818,
821, 823, 825, 836, 837, 838, 1073, 3011, 3012 and the channels 1052, 3001, 3002:
The channels 801, 803, 805 etc. deliver saline concentration in percent by weight. For
example a solution of NaCl with a freezing temperature of -5.3°C reports a measurement
value of 8% on the saline concentration channel 801. The channels 1052, 3001 and 3002
are based on the saturation of salt in liquid. For example a solution of NaCl with a freezing
temperature of -5.3°C reports a measurement value of approx. 36% (8/22 in [%]) o channel
1052. The maximum saturation of NaCl in water is about 22 percent by weight.
Difference between corrected and uncorrected measurement channels:
In the case of uncorrected channels, the status of the channel in the UMB protocol is used
to classify the measurements; if, for example, the ambient temperature is too high the
status can not be 0 (e.g.: 84, the possible error codes are specified in the document
Communication Protocol for Meteorological Sensors
); in this case the freezing temperature
is neither calculated nor transmitted.
In the case of corrected channels the status is transmitted on channel 900. If it is not
possible to calculate the freezing temperature, this is then transmitted as 0°C (or its
equivalent in other units).
Status generation and freezing temperature on the corrected channel:
If it is not possible to calculate the FT status because the ambient temperature is
greater than the temperature set for the sensor (factory setting 5°C), the FT status
is set to 0 and the freezing temperature value is set to 0°C.
If it is not possible to calculate the FT status because the road is dry, the FT status
is set to 1 and the freezing temperature value is set to 0°C.
When a valid FT is calculated, the FT status is set to 2 and the freezing temperature
value is set to the calculated value.
If it is not possible to calculate the FT for other reasons the FT status is set to 3 and
the freezing temperature value is set to 0°C.
If it is not possible to calculate the FT status because the ambient temperature is
lower than -30°C, the FT status is set to 4 and the freezing temperature value is set
to 0°C.
If it is not possible to detect the freezing temperature, because it is below the limits
of the sensor, the FT status is set to 5, freezing temperature below road
temperature -20°C (Tg < (Tu
– 20°C))
If it is not possible to calculate the freezing
temperature, “0” is transmitted for freezing
temperature and “255” is transmitted for “residual salt” on the TLS channel.
A sensor with factory settings will deliver a value of -0.1°C in channel 1065 (freezing
temperature TLS) whenever the road is wet and without salt. The reason for this output is
that in the (G
erman) “Bundesdatenverteiler” (12/2010) the TLS compliant combination of
0°C freezing temperature and 0% residual salt are causing errors in the visualization.
