GLX-RSS-2-300 WL User Manual
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GLX-RSS-2-300 WL Non-Contact Flow Meter
7
Data Protocols
Geolux RSS-2-300 WL flow meter supports the following data protocols:
•
NMEA-like protocol on RS-232 interface that constantly outputs the detected speed,
distance (level), discharge and reflected signal power, and also the current measured tilt
angles of both the surface velocity sensor and the level meter
•
Servicing protocol on RS-232 interface for configuring the unit
•
Request-response protocol on RS-485 interface that allows multiple units to be used on a
single RS-485 bus
•
Modbus-RTU protocol on RS-485 interface which is supported by variety of third-party data
loggers
Support for additional protocols is available upon customer request.
7.1. NMEA Protocol (RS-232)
NMEA protocol is based on the standard protocol family widely used by navigation equipment. NMEA
protocol is sentence oriented and is capable of sending multiple sentences with different information.
The sentence content is designated by the starting keyword which is different for each sentence type.
NMEA sentences are terminated with the checksum which makes this protocol extremely reliable. NMEA
protocol is a single-direction protocol: data is only transmitted from the flow meter. At RS-232 interface
the device periodically outputs following data sentences:
Direct flow measurement report
$RDTGT,D1,S1,L1*CSUM<CR><LF>
$RDTGT:
The keyword sent in the beginning of each detection report. This sentence is
sent whenever there is detected flow.
D1:
The detected flow direction (1 approaching, -1 receding).
S1:
The detected flow speed (speed is reported as speed*10 for m/s, km/h,
mph, fps, fpm and as speed*1 for mm/s and cm/s).
L1:
The detected level of the signal reflection from the water surface.
CSUM:
The check sum of the characters in the report from $ to * excluding these
characters.
Average flow measurement report
$RDAVG,S1*CSUM<CR><LF>
$RDAVG:
The keyword sent in the beginning of the report. This sentence reports
smoothed flow measurement. This is the preferred reading, since it filters
out minor fluctuations in flow speed reading due to waves.
S1:
The detected flow speed (speed is reported as speed*10 for m/s, km/h,
mph, fps, fpm and as speed*1 for mm/s and cm/s).
CSUM:
The check sum of the characters in the report from $ to * excluding these
characters.