FTS SDI-RADAR-300WL User manual

EXTREME ENVIRONMENTS. EXTREMELY RELIABLE.
SDI-RADAR-300WL
Non-Contact Flow Meter
Operating Manual
1.800.548.4264 | www.ftsinc.com
700-SDI-RADAR-300WL-Man Rev 2 11 Apr 2022
Part# 21371

Contact Information
Canadian Headquarters:
1065 Henry Eng Place
Victoria, BC | V9B 6B2 | Canada
www.ftsinc.com
Toll-free: 1.800.548.4264
Local: 250.478.5561
Technical support portal: https://ftsinc.com/customer-care/
Email: [e-mail]

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Contents
1.1 APPROPRIATE USE ..................................................................................................................................... 1
1.2 GENERAL SAFETY INSTRUCTIONS............................................................................................................ 1
2.1 FUNCTIONAL PRINCIPLE ........................................................................................................................... 2
2.2 MEASUREMENT QUALITY INDICATOR..................................................................................................... 3
2.3 RAIN AND WIND......................................................................................................................................... 3
2.4 INTERFERENCE AND MULTIPLE RADARS................................................................................................. 4
2.5 FOGGING AND EVAPORATION ................................................................................................................. 4
2.6 REFLECTIONS.............................................................................................................................................. 5
2.7 SIGNAL STRENGTH .................................................................................................................................... 6
2.8 ELECTRICAL CHARACTERISTICS................................................................................................................ 7
2.9 CABLE PIN-OUT AND WIRING................................................................................................................... 8
2.10 SERIAL RS-232 INTERFACE ........................................................................................................................ 8
2.11 SERIAL RS-485 INTERFACE ........................................................................................................................ 9
2.12 ANALOG 4-20 mA OUTPUT....................................................................................................................... 9
3.1 SITE SELECTION AND FEATURES ............................................................................................................ 10
3.2DETERMINING RADAR FOOTPRINT........................................................................................................ 10
3.3 INSTALLATION POSITION........................................................................................................................ 12
4.1 SERIAL INTERFACES ................................................................................................................................. 14
4.1.1 SERIAL RS-232 INTERFACE............................................................................................................. 14
4.1.2 SERIAL RS-485 INTERFACE............................................................................................................. 14
4.2 DATA PROTOCOLS ................................................................................................................................... 14
4.2.1 NMEA PROTOCOL (RS-232) ........................................................................................................... 15
4.2.2 SERVICING PROTOCOL (RS-232) ................................................................................................... 17
4.2.3 REQUEST-RESPONSE PROTOCOL (RS-485).................................................................................. 20
4.2.4 MODBUS PROTOCOL (RS-485)...................................................................................................... 23
4.2.5 SDI-12PROTOCOL........................................................................................................................... 27
4.2.6 MEASUREMENT COMMANDS ....................................................................................................... 28
4.2.7 X COMMANDS................................................................................................................................. 29

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5.1 CONNECTING THE FLOW METER TO THE CONFIGURATOR................................................................ 31
5.2 CONFIGURING Settings........................................................................................................................... 32
5.2.1 Interfaces......................................................................................................................................... 32
5.2.2 Processing ....................................................................................................................................... 33
5.2.3 Measurement ................................................................................................................................. 37
5.3 CONFIGURING THE UNIT FOR DISCHARGE CALCULATION................................................................. 40
5.3.1 DEFINING PROFILE MANUALLY .................................................................................................... 40
6.1 REAL-WORLD APPLICATION ................................................................................................................... 44
6.2 IMPROVING ACCURACY........................................................................................................................... 46
7.1 TECHNICAL DATA..................................................................................................................................... 47

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SAFETY
1.1 APPROPRIATE USE
Operational reliability is ensured only if the instrument is properly used according to the
specifications in this manual as well as possible supplementary instructions.
WARNING: Inappropriate or incorrect use of the instrument can give rise to
application specific hazards, e.g. damage to system components through
incorrect mounting or adjustment.
1.2 GENERAL SAFETY INSTRUCTIONS
This is a state-of-the-art instrument complying with all prevailing regulations and guidelines.
During the entire duration of use, the user is obliged to determine the compliance of the necessary
occupational safety measures with the current valid rules and regulations for their area.
The safety instructions in this manual, the national installation standards as well as the valid safety
regulations and accident prevention rules must be observed by the user.
For safety and warranty reasons, any invasive work on the device beyond that described in the
operating instructions manual may be carried out only by personnel authorized by the
manufacturer. Arbitrary conversions or modifications are explicitly forbidden.
The safety approval markings and safety tips on the device must also be observed.

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PRODUCT DESCRIPTION
2.1 FUNCTIONAL PRINCIPLE
The SDI-RADAR-300WL flow meter, referred to as the 300WL in this manual, uses radar technology
to provide precise contactless measurement of surface flow velocity and precise distance (level)
measurement from the sensor to the water surface. Contactless radar technology enables quick
and simple sensor installation above the water surface and requires minimum maintenance.
Radar level measurement is achieved by transmitting modulated radar wave in 77 to 81 GHz
frequency range (W-band) and observing returns. Due to the modulation and detection process in
the sensor very precise measurements can be achieved and the sensor is not dependent on the air
temperature, humidity or other parameters of the environment.
Surface velocity measurement is achieved by transmitting an electromagnetic wave in the 24 GHz
frequency range (K-band) and measuring the frequency shift of the electromagnetic wave reflected
from the flowing water surface. The frequency shift is caused by the Doppler effect of the moving
surface on the electromagnetic wave. As the relative speed between the radar sensor and the water
surface increases, the detected frequency shift also increases, thus enabling the flow meter to
precisely determine the surface flow velocity.
The surface velocity radar reports the average surface velocity of the area covered by its beam and
uses complex Kalman filters with physical modelling of the water flow to give stable measurements
even under turbulent conditions. However, moderate waviness of the water surface will improve the
measurement (see Section 2.6). In strongly turbulent water flow, fluctuations in measured data
could be expected as well as somewhat reduced measurement accuracy. If strongly turbulent flow
can be expected at monitoring site, then the filter length of the radar should be configured to 120 or
more.
The flow meter is able to detect water flow traveling at speeds ranging from 0.02 m/s to 15.0 m/s
with precision of 0.01 m/s1. Distance can be measured in range from 0.2 m to 15 m with resolution
of 0.1mm and accuracy of ±2 mm2. The integrated tilt sensor measures the inclination angle of the
sensors and the flow velocity measurement is automatically cosine-corrected according to the
measured mounting tilt angle.
Calculation of the flow (discharge) is done internally by combining surface velocity measurement
and level measurement information with the configured cross section of the river or channel.
Configuration of the measurement parameters like profile cross section, material of the edges,
location of the sensor above the water can be easily set with the configuration application (refer to
Chapters 5 and 6). When parameters are set properly the sensor will calculate flow with accuracy
around ±1% compared to ADCP measurement for the same location. Measurements of surface
velocity and water level will also be available in parallel to the flow readings on sensor digital
communication interfaces.
10.04 mph to 33.55 mph with a precision of 0.02 mph
27.87 in to 49 ft 2.2 in with a resolution of 0.004 in and accuracy of ±0.08 in

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2.2 MEASUREMENT QUALITY INDICATOR
The 300WL constantly calculates signal parameters in the signal processing algorithms and will
report measurement quality (signal quality) with the measurement data report. The quality indicator
value can be used to better interpret data in the analysis software.
The Measurement Quality Indicator (signal quality) values are:
3->unacceptable,
2 ->low,
1->good,
0->excellent
It is up to every user to interpret the quality indicator value for their application based on their
knowledge of the site. The general recommendation is that measurements with quality indicator 3
cannot be trusted, value 2 could be questionable and values 1 and 0 are very good and accurate.
For example: A radar is mounted on a railway bridge (a common application).
Measurements will be of high quality most of the time except when a train is passing due to
the extensive vibrations. The radar will still report measurements, but the values could be
skewed. However, the measurement quality indicator value for measurements during that
time frame will be higher, indicating the data should be questioned.
2.3 RAIN AND WIND
The 300WL has integrated internal software filters to filter out effects of rain, fog or wind. However,
these filters have some limitations imposed by environmental conditions (i.e. precipitation). The
majority of measurement inaccuracies caused by environmental factors can be solved by proper
sensor installation.
For rain and snow suppression, the most effective solution is to mount the radar so that the flow
meter points upstream and the water flows towards the radar. As rain falls down and the radar is
tilted downwards, rain droplets will move away from the radar, while the water flows towards the
radar. The radar can then easily distinguish the water movement from rain movement. To further
improve rain filtering, the radar should be configured to report only incoming direction of water
flow. In this case, the radar will completely ignore all movement with direction going away from the
sensor. However, for sites that has water flow in both directions, the radar sensor should be
configured to report both incoming and outgoing flow by selecting the “both direction” setting in the
radar sensor.
Additional rain suppression can be implemented by mounting the radar below a structure so that
the first 1 to 2 meters in front of the radar are free of rain. As the energy of the radar beam drops
exponentially with distance, the radar is most sensitive to the rain directly in front of the radar. If the
radar instrument is being mounted on a bridge, if possible, it should be mounted below the bridge
instead of on the side of the bridge, so that the bridge provides cover from the rain directly in front
of the instrument.

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The influence of the wind on the accuracy of measured data is, in most cases, small and can be
neglected. The only exception is strong wind as it will create surface waves that are traveling in a
different direction from the water flow. This can affect surface measurement accuracy.
2.4 INTERFERENCE AND MULTIPLE RADARS
The surface velocity radar operates in K band, in frequency range around 24.125 GHz. Frequency
stability and phase noise of the internal oscillator is very good and always trimmed in factory to a
precise central frequency making the likelihood of two devices working on the exact same frequency
to cause interference highly unlikely. The Doppler frequency shift caused by water in the speed
range up to 15 m/s is measured in kHz frequency shift. As this frequency shift is relatively small in
comparison to the central frequency, in most cases below 0.00005%, it will be required to keep the
difference between central frequencies of two radars in the same range to get interference.
The distance measurement radar operates in the W-band from 77 GHz to 81 GHz with continuous
linear frequency modulation within the frequency range. Interference between two or more sensors
will require precise coordination of the central frequencies with a timing synchronization in a range
of 25 ns between each other. Such synchronization is very complex to achieve so the interference
probability between several radars on the same location is very small.
Similarly, is very unlikely that other radiation sources in K band or W band in the vicinity will affect
the 300WL measurements. Some wideband radiation sources can introduce small impulse
interference for a short period of time, but this is very unlikely to affect measurements reported by
the radar.
2.5 FOGGING AND EVAPORATION
Generally, radar sensors are not affected by fog or evaporation. However, heavy evaporation with
high water density in the atmosphere can affect measurement accuracy. A very high amount of
evaporation can introduce reflections and can affect measurement on both sensors, with greater
inaccuracies seen on the surface velocity measurements.
The best solution for the surface velocity sensor measurements in heavy evaporation is to use the
outbound flow direction and to configure the sensor with only the downstream directional filter. As
evaporation is traveling upwards from the water surface, using the directional filter for water that is
inbound or approaching to the radar will solve the problem in most of the cases.
The best solution for the distance measurement is to increase the average period to get a better
average distance value. As evaporation is a naturally very turbulent event with a significant
difference in atmospheric water density over the surface area over time, averaging of the distance
measurement spectrum solves the accuracy problem.

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2.6 REFLECTIONS
Water is very reflective medium for the radar waves and most of the power transmitted from radar
transmitter will be reflected from the water surface. Reflections of the radar transmitted power
beam follow the same physical laws as in optics in that part of the power is reflected towards the
radar, part of the power is reflected away from the radar, and a small part of power is absorbed by
the water. Depending on the surface roughness, the incident angle ratio between power reflected
away from the radar and towards the radar can significantly vary.
Figure 2-1: Reflected power
In the case of level meter where the incident angle of the transmitted radar beam (yellow arrow) to
the water is around 90°, most of the power is reflected back to the sensor (blue arrow) and only a
small portion of the transmitted power will be dispersed in all directions (red arrows). In general, the
ratio between power reflected to the sensor and power dispersed in all directions due to surface
roughness is very small and it is unlikely that dispersed energy will cause additional multipath
problems due to additional reflections from surrounding objects.
The situation for the surface velocity radar is little more complex as the angle between the
transmitted radar beam (yellow arrow) and water is around 45°. In calmer conditions, most of the
power is reflected in the opposite direction from the radar (red arrow) at around a 45°. Reflection in
the direction of the radar sensor (blue arrow) is always smaller and can be comparable with the
dispersed power in all directions (gray arrows). However, generally, a rougher water surface will lead
to a stronger reflection being returned to the radar and a greater SNR (signal to noise) ratio which
enables more accurate measurements. The surface velocity radar is designed to achieve accurate

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measurements even in environments with very small SNR so the required surface roughness of
1mm is usually enough for precise measurements.
When selecting the location for the surface velocity sensor additional care must be taken to avoid
reflected power away from the radar (red arrow) to hit moving objects (gray cloud) on the side of the
water channel as this can cause additional inbound reflection to the radar and can significantly
affect measurement accuracy. Installations where pedestrians, cars or other objects are moving in
front of the sensor closer than 75 m should be avoided as it is proven in practice that it can cause
problems.
2.7 SIGNAL STRENGTH
Good signal-to-noise ratio (SNR) is the most important parameter of the radar signal that provides
accurate and stable surface velocity measurements. When more radar energy is reflected back from
the water surface to the radar sensor, the overall signal strength is higher. When less energy is
reflected back, as it is when the water surface roughness is lower, the signal strength is lower. If the
amount of noise present in the signal remains the same, when the surface roughness is lower, SNR
will drop. To improve SNR internally, the radar uses low-noise programmable gain amplifier (PGA). If
the strength of reflected signal is ow, the radar will increase gain level on PGA. If the strength of
reflected signal is higher, gain level will be automatically reduced.
The best indication of good signal strength is the PGA value in the radar status report messages.
This value is automatically changed with the AGC (automatic gain control) algorithm in the radar.
Minimal possible gain is 1 and maximal possible gain is 200. The best measurement results are
obtained when the PGA gain level is between 5 and 100; a PGA gain lower than 5 means that the
reflected signal is very strong and it can oversaturate the receiver, which could result in reduced
accuracy. Gain 200 should be avoided as it is usually an indication of very low reflections from the
water surface.

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2.8 ELECTRICAL CHARACTERISTICS
PARAMETER
MIN
TYPICAL
MAX
UNIT
Communication interface:
RS-232 interface speed
RS-485 interface speed
1200
1200
-
-
115200
115200
bps
bps
Radar Sensor
Frequency
Radiated power (EIRP)
Sensitivity
Beam-width (3dB) – Azimuth
Beam-width (3dB) – Elevation
Measurement range
Resolution
Accuracy
Installation height above H2O
24.075
-
-108
-
-
0.02
(0.065)
0.01
(0.032)
-
-
-
24.125
-
-110
12
24
-
-
-
-
1
-
-
24.175
20
-112
-
-
15.0
(49.21)
-
-
-
15
(49.2)
GHz
dBm
dBm
⁰
⁰
m
(ft)
m/s
(ft/s)
%
m
(ft)
Radar Level Sensor
Frequency
Beamwidth (3dB) – Azimuth
Beamwidth (3dB) – Elevation
Resolution
Accuracy
Distance
77
-
-
1
(0.04)
-
-
0.2
(0.656)
-
12
12
-
-
2
(0.08)
-
81
-
-
-
-
-
-
15
(49.2)
Ghz
-
-
mm
(in)
mm
(in)
m
(ft)
Power supply voltage 9.0 12.0 27.0 V
Power
Operational Mode
Sleep Mode
-
-
1650
350
-
-
mW
mW
Alarm output maximal current
- - 60 mA
Alarm output maximal voltage
- - 30 VDC
Analog output maximal voltage - - 30 VDC
Operational temperature range -40
(-40) +85
(+185)
⁰C
(°F)
Angle compensation 0 30 75 deg
Installation height above water
0.2
(0.656)
-
-
20
(65.6)
m
(ft)
Sample Rate
Discharge
Velocity
-
-
1
10
-
-
sps
sps
Ingress protection rating IP68 - - -
Mechanical
-
-
150x200x250
(5.9x7.87x9.84)
-
-
mm
(in)

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2.9 CABLE PIN-OUT AND WIRING
The sensor is supplied with an open-end cable consisting of 12 wires coded as shown in Table 2-2.
Users can attach their own connector, connect the cable via a terminal strip, or wire it directly to
device electronics. Refer to Table 2-2 for wiring details.
Table 2-1: Cable wiring codes
PIN #
COLOUR
PIN NAME
PIN DESCRIPTION
1
White
GND
This pin should be connected to the ground (negative) pole of
the power supply
2
Brown
+Vin
Power supply. Power supply voltage must be 9 to 22 VDC,
and the power supply must be able to provide at least 0.65W.
3 Green RS232 – TxD RS-232 data transmit signal.
4
Yellow
RS232 – RxD
RS-232 data receive signal.
5
Grey
GND
Signal ground.
6
Pink
CAN – H
CAN2.0B high signal (optional)
7
Blue
CAN – L
CAN2.0B low signal (optional)
8
Red
SDI-12 Data
SDI-12 Data line
9
Orange
RS485 – D-
RS-485 data transmitter/receiver low signal.
10
Dark Red
RS485 – D+
RS-485 data transmitter/receiver high signal.
11
Black
Alarm1 SW or
4-20mA secondary
(optional)
Alarm 1 – open collector switch signal max. 60mA
12
Purple
4-20 mA
Sink for 4-10 mA analog interface. Connect sensing device as
pull-up to sink the current
2.10 SERIAL RS-232 INTERFACE
Serial RS-232 interface is implemented as standard PC full-duplex serial interface with voltage levels
adequate for direct connection to PC computer or other embedded device used for serial RS-232
communication.
When the RS-232 interface is connected to a standard DB-9 PC connector, the TxD line (green wire) is
connected to pin 2 and the RxD (yellow wire) is connected to pin 3. In order for the serial interface to
operate properly, an additional connection of the signal GND (grey wire) is needed on pin 5 of the
DB-9 connector.

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2.11 SERIAL RS-485 INTERFACE
Serial RS-485 interface is implemented as standard industrial half-duplex communication interface.
Communication interface is internally protected against short-circuit and overvoltage. Depending on
the receiving device interface can be used with only two wires (D+ dark red wire & D- orange wire) or
in some cases ground connection (signal GND gray wire) is also required. For more details, consult
the receiver specification.
Most common communication protocol used with RS-485 interface is Modbus-RTU but other
protocols are also available. Details of communication protocols are described later in this manual.
2.12 ANALOG 4-20 MA OUTPUT
Analog current 4 – 20 mA output is provided for easier compatibility with older logging and control
systems. Output is implemented as current sink architecture with common ground. Maximal voltage
applied to the sink can go up to 30 VDC providing greater flexibility in connection of the sensor to
PLCs, loggers, or data concentrators.
Signal range and function for 4 – 20 mA analog output can be configured in the setup application so
the sensor will be able to signal the best suitable value range with the available current range.
The sensor’s current step has a limiting resolution of 0.3 μA. Ensure the minimal and maximal
values representing 4 mA and 20 mA have sufficient resolution for system requirements.

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INSTALLATION
3.1 SITE SELECTION AND FEATURES
When determining where to mount the 300WL a direct, unobstructed line to the water surface is
available for both the surface velocity sensor and the level sensor. Any close object in the vicinity of
the sensor can reduce accuracy and introduce offsets in measurements. The best practice is to have
a 1m zone around both sensors clear of obstructions.
The height of the instrument above the water surface and the inclination determine the area on the
surface that is covered by the radar beam (see Section 3.2). This measurement area should be clear
of any obstacles. There should be no vegetation between the radar and the measurement area
because it could affect measurement accuracy.
Additionally, for the level meter, the water surface directly below the unit should be calm, clean of
vegetation, rocks, sand deposition or other obstacles that could affect measurement. The surface
velocity radar should be pointed upstream (water flowing towards the radar).
The structure holding the instrument (pole, bridge fence, etc.) must be solid and without vibrations.
Vibrations of the mounting structure can affect the sensor’s ability to eliminate detected obstacles
resulting in inaccurate measurements. Vibrations should be avoided or reduced by any applicable
means. If mounting at a site that has periodic vibrations (i.e. train bridge) be aware of the
measurement quality indicator during a vibration period in order to determine the reliability of the
data. Details can be found in Section 2.1.
Installations where pedestrians, cars or other objects are moving in front of the flow sensor closer
than 75 m should be avoided to prevent reflected power from those objects being received by the
radar and significantly affecting measurement accuracy (refer to in Section 2.6 and Figure 2-1 for a
detailed explanation).
3.2 DETERMINING RADAR FOOTPRINT
The radars’ paths and footprints are calculated based on 3 dB signal drop (half signal power) due to
the antenna pattern. Most of the return energy is reflected from the inside of the calculated
footprints (ellipse for the surface velocity sensor and circle for the level sensor – see Figure 3-1), but
some energy could be also received from objects outside of the footprint. Although the sensors
have an internal signal processing algorithm to filter such reflections, large objects close to the
footprint perimeter can cause some measurement inaccuracies. Therefore, it is recommended to
keep the zone around the target shape of the radars as clear as possible for the best measurement
accuracy.

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Figure 3-1: Radars’ paths and footprints
Table 3-1: Calculation of Sensor Footprints
METRIC IMPERIAL
Height[H]
L [m]
D
1
[m]
D
2
[m]
R [m]
Height[H]
L [ft]
D
1
[ft]
D
2
[ft]
R [ft]
0.3 m
0.3
0.3
0.2
0.06
0.98 ft
0.98
0.98
0.66
0.20
0.5 m
0.5
0.5
0.3
0.11
1.64 ft
1.64
1.64
0.98
0.36
1 m
1.0
0.9
0.3
0.21
3.28 ft
3.28
2.95
0.98
0.69
2 m
2.0
1.8
0.6
0.42
6.56 ft
6.56
5.9
1.97
1.38
3 m 3.0 2.7 0.9 0.63 9.84 ft 9.84 8.86 2.95 2.07
4 m 4.0 3.6 1.2 0.84 13.12 ft 13.12 11.81 3.94 2.76
5 m
5.0
4.5
1.5
1.05
16.4 ft
16.4
14.76
4.92
3.45
6 m
6.0
5.3
1.8
1.26
19.69 ft
19.69
17.39
5.90
4.13
7 m
7.0
6.2
2.1
1.47
22.97 ft
22.97
20.34
6.89
4.82
8 m
8.0
7.1
2.4
1.68
26.25 ft
26.25
23.29
7.87
5.51
9 m 9.0 8.0 2.7 1.89 29.53 ft 29.53 26.25 8.86 6.20
10 m 10.0 8.9 3.0 2.10 32.81 ft 32.81 29.20 9.84 6.89
11 m
11.0
9.8
3.3
2.31
36.01 ft
36.01
32.15
10.83
7.58
12 m
12.0
10.7
3.6
2.52
39.37 ft
39.37
35.10
11.81
8.27
13 m
13.0
11.6
3.9
2.73
42.65 ft
42.65
38.06
12.80
8.96
14 m
14.0
12.5
4.2
2.94
45.93 ft
45.93
41.01
13.78
9.65
15 m 15.0 13.4 4.5 3.15 49.21 ft 49.21 43.96 14.76 10.34

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3.3 INSTALLATION POSITION
Ensure the selected site and radar paths meets the criteria as described in Sections 3.1 and 3.2.
The minimum mounting height above the water’s surface is 0.2 m; however, it is recommended to
mount the sensor from 0.5 m – 15 m above the water’s surface. Sensor should be mounted on a
vertical pole with inclination tolerance of ±5° to the vertical plane reference.
Figure 3-2: Installation Position
For optimal operation and results, the velocity sensor should be pointed directly upstream, so that
the water flows towards the instrument and with the radar beam parallel with the water flow (see
Figure 3-3). Any deviation from the parallel water flow direction will introduce an offset to the
measurement value and the measured value will be lower than the actual surface velocity of the
water.
Figure 3-3: 300WL mounting position relative to water flow – aerial view
0.2 m (7.87 in)
Minimum installation height
0.5 m – 15 m (1.64 ft – 49.21 ft)
Recommended installation height
15 m (49.21 ft)
Maximum installation height
Water flow
Clear of moving objects to 75 m (246 ft)
Water flow
Bank
Bank

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Additionally, moderate waviness of the water surface will improve the velocity measurements. If the
water flow is strongly turbulent, fluctuations in measured data could be expected as well as
somewhat reduced measurement accuracy. If strongly turbulent flow can be expected at the
monitoring site, then the filter length of the radar should be configured to 120 or more.

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DATA INTERFACES AND PROTOCOLS
4.1 SERIAL INTERFACES
The 300 WL offers the following serial interfaces, for ease of integration with existing SCADA/telemetry:
1) Serial RS-232 interface
2) Serial RS-485 interface
4.1.1 SERIAL RS-232 INTERFACE
Serial RS-232 interface is used for direct connection of a unit with a computer. The serial interface is
used both for retrieving measurements and for configuring the device using the PC application (see
Chapter 5).
Default communication parameters are:
Bitrate: 9600 bps
Data bits: 8
Stop bits: 1
Parity: None
An NMEA-like communication protocol is used to deliver flow measurements over the RS-232
interface. Detailed description of the protocol is given in the Section 4.2.
4.1.2 SERIAL RS-485 INTERFACE
The serial RS-485 interface is used for connecting multiple flow meters on a single RS-485 bus to a
single data logger. The main difference from the protocol used over RS-232 interface is that the flow
measurements are not reported automatically but are instead reported only after being requested
by the master device (data logger unit). Detailed description of the protocol is given in the Chapter 4.
Default communication parameters are:
Bitrate: 9600 bps
Data bits: 8
Stop bits: 1
Parity: None
4.2 DATA PROTOCOLS
The 300 WL supports the following data protocols
1) NMEA protocol on RS-232 interface that constantly outputs the detected speed,
reflected signal power, and the current measured tilt angle
2) Servicing protocol on RS-232 interface for configuring the unit
3) Request Response Protocol on RS-485 interface that allows multiple units to be used on a
single RS-485 bus

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4) Modbus RTU protocol on RS-485 interface which is supported by a variety of third-party data
loggers
5) SDI-12 protocol on the SDI-12 data line
4.2.1 NMEA PROTOCOL (RS-232)
NMEA protocol is based on the standard protocol family widely used by the 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 single-direction protocol: data is only transmitted from the flow
meter.
At RS-232 interface the device periodically outputs the following data sentences:
Direct flow measurement report: $RDTGT,D1,S1,L1*CSUM<CR><LF>
$RDTGT: The keyword sent on 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 (speed3is reported as speed*10 for m/s, km/h,
mph, fps, fpm and as speed*1 for mm/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 on 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 (speed1is reported as speed*10 for m/s, km/h,
mph, fps, fpm and as speed*1 for mm/s).
CSUM: The check sum of the characters in the report from $ to * excluding these
characters.
Tilt angle report: $RDANG,A*CSUM<CR><LF>
$RDANG: The keyword sent on the beginning of each angle report.
A: The measured tilt angle, in degrees, 0 being horizontal.
CSUM: The check sum of the characters in the report from $ to * excluding these
characters.
3In the radar sensor setting it is possible to select km/h, mph, fps, fpm or mm/s for the speed reporting

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Signal SNR report: $QOS,Q1,Q2*CSUM<CR><LF>
$QOS: The keyword sent on the beginning of each quality of signal report.
Q1: Quality of signal estimate based on sensor vibration.
Q2: Quality of signal estimate signal quality.
CSUM: The check sum of the characters in the report from $ to * excluding these
characters
Quality of signal factor:
0 – Excellent measurement quality
1 – Good measurement quality
2 – Low measurement quality
3 – Unacceptable measurement quality
Water level report: $LVL,L1,L2,T1,L3,L4,S*CSUM<CR><LF>
$LVL: The keyword sent on the beginning of each level report.
L1: Current distance from sensor to water, in defined units, 0 being sensor
reference plane. If reporting -4 then there is no detected level.
L2: Average distance from sensor to water, in defined units, 0 being sensor
reference plane. If reporting -4 then there is no detected level.
T1: Electronic temperature (in °C).
L3: Current relative detected level, in defined units, 0 being sensor reference
plane.
L4: Average relative detected level, in defined units, 0 being sensor reference
plane.
S: Measurement SNR (in dBm).
CSUM: The check sum of the characters in the report from $ to * excluding these
characters.
Discharge report: $DIS,D*CSUM<CR><LF>
$DIS: The keyword sent on the beginning of each discharge report.
D: The measured discharge, in defined units.
CSUM: The check sum of the characters in the report from $ to * excluding these
characters.