Geolux LX-80S User manual

Copyright ©2023 Geolux d.o.o. All rights reserved.
LX-80S
Snow Level Sensor
User Manual
v2.5.5

Starting Point
Thank you for purchasing the Geolux LX-80S snow level sensor! We have put together the
experience of our engineers, the domain knowledge of our customers, the enthusiasm of our team,
and the manufacturing excellence to deliver this product to you.
You may freely rely on our eld-proven radar technology. The use of top-quality components and
advanced signal processing algorithms ensures that the Geolux snow level sensor can be used in
various applications and environments.
We have created this User manual in order to assist you with setting up and using the Geolux
instrument.
Should there be any questions left unanswered, please feel free to contact us directly:
Geolux d.o.o.
Ljudevita Gaja 62
10430 Samobor
Croatia
E-mail: [email protected]
Web: www.geolux.hr

Contents
1. Introduction 1
2. Electrical Characteristics 2
3. Connector Pin-Out 3
3.1. Serial RS-232 Interface 4
3.2. Serial RS-485 Interface 4
3.3. Analog 4 – 20 mA Output 5
3.3.1. Devices With Serial Numbers Not Starting With LX15-4 5
3.3.2. Devices With Serial Numbers Starting With LX15-4 8
3.4. SDI-12 Interface 8
4. Installing the Snow Level Sensor 9
4.1. Rain and Wind 10
4.2. Interference and Multiple Radars 10
4.3. Fogging and Evaporation 10
4.4. Reections 11
4.5. Relative Measurement 11
4.6. Units 12
4.7. Radar Calibration 12
5. Radar Settings 13
6. Data Interface 20
6.1. Serial RS-232 Interface 20
6.2. Serial RS-485 Interface 20
7. Data Protocols 21
7.1. NMEA Protocol (RS-232) 21
7.2. Servicing Protocol (RS-232) 22
7.3. Modbus Protocol (RS-485) 29
7.3.1. Modbus Input Registers 35
7.4. SDI-12 Protocol 37
8. Geolux Instrument Congurator 42
9. Troubleshooting 46
10. Appendix A – Mechanical Assembly 53

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LX-80S Snow Level Sensor
1
Introduction
Geolux LX-80S is the innovative snow level sensor that uses advanced 80 GHz radar technology
to accurately measure the distance from the sensor down to the surface of the snow. The LX-
80S offers superior performance compared to traditional ultrasound devices used for snow depth
measurement.
Installing and maintaining the LX-80S is easy, and the device can cover a long detection distance
of up to 15 meters. The radar technology allows for non-invasive measurement from above the
snow, ensuring that the snow’s structure is not disturbed in any way.
The LX-80S has many applications, including continuous monitoring of snowpack buildup and
melting, making it essential for meteorological monitoring, hydrological planning, avalanche
warning, and ski resorts. The device provides accurate data on snow depth, which is crucial for
many industries, especially those that depend on snow conditions.
Unlike ultrasound devices that require temperature compensation due to their distance
measurement being affected by air density, the LX-80S radar is not impacted by such
environmental changes. Moreover, ultrasonic sensors are more susceptible to negative effects from
snowfall or icicles, which can form close to the device. However, the LX-80S radar uses advanced
signal processing algorithms for precipitation detection, and has a narrow radar beam of only 5°,
which prevent such issues.
The low power consumption of the instrument, small form factor and a rugged enclosure make this
instrument easy to setup and use.

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Electrical Characteristics
The electrical characteristics of the Geolux LX-80S snow level sensor are given in Table 1.
Table 1. Electrical Characteristics
Parameter MIN TYP MAX Unit
Communication interface:
RS-232 interface speed
RS-485 interface speed
9600
9600
115200
115200
bps
bps
Radar Sensor
Frequency
Beam-width (3dB) – Azimuth
Beam-width (3dB) – Elevation
77.000
5 (±2.5)
5 (±2.5)
81.000 GHz
°
°
Power supply voltage 9.0 12.0 27.0 V
Power
Operational
Standby mode
Sleep mode
360
150
30
600 mW
mW
mW
Operational temperature range -40 +85 °C
Measurement range 0.4 15 m
Accuracy 1 mm
Resolution 0.5 mm
Ingress Protection Rating IP68
Mechanical ф65 x H78 mm

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LX-80S Snow Level Sensor
3
Connector Pin-Out
The snow level sensor uses robust IP68 circular M12 connector with 12 positions and a mating
cable, both delivered standardly with the instrument. The connector and cable details are shown in
Picture 1 while Table 2 gives a detailed description of each pin.
Picture 1. Snow Level Sensor Connectors
Table 2. Connector and Cable Pin-out
Pin No. Wire Color Pin Name Pin Description
1 White GND This pin should be connected to the ground (neg-
ative) pole of the power supply.
2 Brown +Vin This is the pin with the instrument’s power supply.
The snow level sensor power supply voltage must
be between 9 VDC to 27 VDC, and the power sup-
ply must be able to provide at least 0.65 W.
3 Green RS232 – TxD RS-232 data transmit signal.
4 Yellow RS232 – RxD RS-232 data receive signal.
5Grey GND Signal ground.
6 Pink CAN – H CAN2.0B high signal. (optional)
7 Blue CAN – L CAN2.0B low signal. (optional)
8 Red V+ Output power supply (+Vin) for supply of exter-
nal optional equipment and for use with analog
4 – 20 mA output.
4 – 20 mA LOOP+ * Positive connector for 4 – 20 mA output loop.
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 SDI-12 SDI-12 communication interface.
12 Purple 4 – 20 mA Output Analog 4 – 20 mA output.
4 – 20 mA LOOP- *Negative connector for 4 – 20 mA output loop.
* 4–20 mA LOOP+ and LOOP- is used on devices with serial numbers starting with LX15-4 (e.g. LX15-401234)

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LX-80S Snow Level Sensor
3.1. 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 computers or other embedded devices used for serial
RS-232 communication.
When the RS-232 interface is connected to a standard DB-9 PC connector, TxD line (green wire)
is connected to pin 2 and RxD (yellow wire) is connected to pin 3. In order for the serial interface
to operate properly, an additional connection of signal GND (grey wire) is needed on pin 5 of the
DB-9 connector. Optionally, Geolux can supply a cable with DB-9 connector connected to the
cable. This requirement must be specied when placing an order.
Several communication protocols are available. Additional custom protocols can be implemented
on request. Detailed description of communication protocols is given in chapter 7 of this user
manual.
Picture 2. Serial RS-232 DB-9 Cable
3.2. Serial RS-485 Interface
Serial RS-485 interface is implemented as standard industrial half-duplex communication
interface. The communication interface is internally short-circuit and overvoltage protected.
Depending on the receiving device, the interface can be used with only two wires (D+ dark red
wire & D- orange wire) while in some cases the ground connection (signal GND grey wire) is also
required. For more details please consult receiver specication.
The most common communication protocol used with RS-485 interface is Modbus-RTU, but other
protocols are also available on request. Detailed description of communication protocols is given in
chapter 7 of this user manual.
Geolux recommends using Waveshare USB TO RS232/485/TTL converter for connecting Geolux
instruments to computers without a native RS-232 port.
https://www.waveshare.com/catalog/product/view/id/3629/s/usb-to-rs232-485-ttl/category/37/

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LX-80S Snow Level Sensor
3.3. Analog 4 – 20 mA Output
Analog current 4 – 20 mA output is provided for easier compatibility with older logging and control
systems. The implementation of the 4 – 20 mA output differs depending on the serial number of
the level meter as explained in the next two chapters.
3.3.1. Devices With Serial Numbers Not Starting
With LX15-4
The output is implemented as current sink architecture with common ground. Maximal voltage
applied to the sink can go up to 30 VDC, providing greater exibility in connection of the sensor to
PLCs, loggers, or data concentrators.
Signal range and function for 4 – 20 mA analog output can be congured in the setup application
so the sensor will be able to signal best suitable value range with available current range. Current
step in the sensor is 0.3 µA, which limits the resolution, so care must be taken while setting the
minimal value to be represented by 4 mA and the maximal value to be represented by 20 mA, so
the resolution is sufcient for the system requirements.
Measurement of the current by the client device (logger, PLC, modem etc.) must be implemented as
the high side current measurement as shown in Picture 4. If a sensing resistor is used, resistance
should be selected from the range of 10 Ω up to 500 Ω, with a recommended value of 100 Ω for
the sensing resistor.

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LX-80S Snow Level Sensor
Picture 4. High Side Current Measurement for the 4 – 20 mA Analog Output
Connection to Schneider TM3AM6 analog input module
The TM3AM6 analog module contains 4 analog inputs, marked I0 to I3. Each analog input consists
of two connectors, marked as I+ and I-. Each analog input can be congured to work either as
analog voltage input (0 – 10 V or -10 to +10 V), or as analog current input (0 – 20 mA or 4 – 20
mA). This is the wiring diagram from the TM3AM6 user manual:

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LX-80S Snow Level Sensor
In order to connect the Geolux instrument to the TM3AM6 module, the rst step is to congure the
selected input port as analog current input operating on 4 – 20 mA range. This is done by using
Schneider software. After the analog input module is congured, the second step is to connect the
Geolux instrument to the TM3AM6 module, according to the following schematic diagram:
It is important to note that the 4 – 20 mA wire from the Geolux instrument should be connected to
negative (-), not positive (+) terminal of the analog input port.

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LX-80S Snow Level Sensor
3.3.2. Devices With Serial Numbers Starting
With LX15-4
In this revision the LX-80 uses two wires for 4-20 mA: LOOP+ and LOOP-, which should be con-
nected to the LOOP+ and LOOP- terminals on the PLC or the datalogger directly. It is important to
note that the instrument still needs to get a separate power supply over white and brown wires.
The sensor can not be used in two-wire connection - 4-20 mA wires are used only for measure-
ment, not to provide the power to the instrument. Finally, the 4-20 mA LOOP must be separate
from the power supply loop, and there should be no common ground nor common V+ between the
4-20 mA loop and the instrument power supply.
3.4. SDI-12 Interface
SDI-12 interface is widely used to connect hydrological equipment to dataloggers. SDI-12 uses
a single communication line, and very slow speed communication to enable the use of very long
communication cables.
For hydrological applications, SDI-12 communication interface is a valid option and the instrument
is natively able to communicate directly with SDI-12 master devices (dataloggers etc.).

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LX-80S Snow Level Sensor
4
Installing the Snow Level Sensor
The snow level sensor must be installed above the snow, pointing directly towards the snow
surface. The minimum distance between the sensor and the snow must not be less than 0.4 m. It is
recommended to keep the distance between the sensor and the snow at least 1 metre. The sensor
should be directed at a 90° angle relative to the snow surface. To simplify instrument installation,
the sensor reports its tilt angle over communication interfaces. The eld technician can use the PC
application to connect to the sensor and check that the tilt angle of the unit is 0° (so that the angle
between the radar beam and the snow is 90°).
When mounting the sensor, special care must be taken to ensure a clear zone around the snow level
sensor. Any close object in the vicinity of the sensor can reduce accuracy and introduce offsets or errors
in measurements.
Vibrations of the mounting structure can also affect measurements and should be reduced by any
applicable means.
Picture 5. shows how the snow level sensor should be installed.
Picture 5. Installing the Snow Level Sensor

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LX-80S Snow Level Sensor
4.1. Rain and Wind
The internal signal processing lters of the Geolux LX-80S snow level sensor are designed to
lter out the effects of fog, wind, rainfall and snowfall on the snow depth measurement. These
lters, however, have some limitations. The majority of measurement inaccuracies caused by
external environemntal factors can be solved by proper sensor installation. The guidelines for the
proper installation can be seen in Picture 5. on the previous page of this user manual. It is strongly
recommended to follow these guidelines, specically with regards to the distance of the snow level
sensor from the vertical pole.
Inuence of the snowfall and light rain on the accuracy of the measurement is in most cases
neglectable. Very heavy rain could disrupt the measurements under certain circumstances, but by
conguring the instrument to use longer lter size, this effect can be mitigated.
4.2. Interference and Multiple Radars
The distance measurement radar operates in W-band from 77 GHz to 81 GHz with linear
frequency modulation, modulating the signal continuously in the aforementioned frequency range.
For interference between two or more sensors to occur, it would be required to keep their central
frequencies very precise and the timing synchronization of radars should be kept in the range of 25
ns to each other. Such synchronization is very complex to achieve so the interference probability
between several radars on the same location is very small.
It is possible that some wideband radiation sources can introduce small and impulse interferences
for a short period of time, but this should not, or is very unlikely to affect measurements reported
by the radar sensor.
4.3. Fogging and Evaporation
Generally, radar sensors are not affected by fog or evaporation of water unless very heavy
evaporation is present and water density in the air is very high.
The best solution for distance measurement is, in most cases, to increase the average period of the
averaging lter. As evaporation is naturally a turbulent event with signicant difference in density
over the surface area and in time, averaging of the distance measurement spectrum solves the
accuracy problem in such conditions.

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LX-80S Snow Level Sensor
4.4.Reections
Snow reects radar signals very well, which means most of the power of a wave transmitted from
the radar transmitter will be reected from the surface of the snow.
Reections of the radar transmitted power beam follow the same physical laws as in optics,
and every time a radar beam hits the snow surface, part of the power is reected away from
the radar, part of the power is reected towards the radar, and only a small part of the power is
absorbed by the snow. Depending on the surface roughness and incident angle, the ratio between
power reected in the direction away from the radar and in the direction back towards the radar
can signicantly vary. As incident angle for radars in xed, only the roughness of the surface
determines the ratio in this case.
In the case of snow level sensors where the incident angle of the transmitted radar beam to the
snow is around 90°, most of the power is reected back to the sensor and only a small portion of
the transmitter power will be dispersed in all directions. The ratio between the power reected to
the sensor and the power dispersed in all directions is dependent on the surface roughness but
generally, a very small amount of energy is dispersed, and it is very unlikely that the dispersed
energy will cause additional multipath problems due to more reections from surrounding objects.
4.5. Relative Measurement
Each sensor unit measures the distance between the sensor and the rst detected object. For
snow depth measurement, it is preferred to report the actual snow level from the ground to the
surface of the snow. That is why we offer relative measurement, which is calculated relative to the
mounted sensor height. Sensor height is dened as the distance from the mounted sensor position
to the ground. This distance is a xed value unique to every mounted unit. It can be set in two
ways.
First is by setting the sensor height parameter directly using any of the communication protocols
described in the following sections. After setting the sensor height, the relative measurement will
be calculated according to the following formula:
RM=SH-D,
where:
RM= relative measurement,
SH=sensor height,
D=measured distance from the sensor to the snow.

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LX-80S Snow Level Sensor
For example, if the sensor is mounted 6.35 m above the ground, and the measured distance from
the sensor to the snow surface is 4.34 m, then the snow depth is calculated as the difference of
these two values: 6.35 m – 4.34 m = 2.01 m.
In this case the sensor will report 4.34 m as the measured snow level and 2.01 m as the measured
relative level.
Alternatively, it is possible to set the sensor height indirectly, using the staff gauge measurement.
In this case, the staff gauge measurement needs to be taken directly underneath the position
of the mounted sensor. When setting the sensor height using staff gauge height, the following
formula will be used to calculate the sensor height:
SH=D+SG,
where:
SH=sensor height,
D=measured distance from the sensor to the snow,
SG=staff gauge measurement.
For example, the sensor is mounted at an unknown height above the ground and using a staff
gauge it is determined that the snow depth at that given time is 1.34 m. The sensor detects snow
at the distance of 6.02 m. By setting the value 1.34 m as the staff gauge measurement at the same
time when the device measures the distance as 6.02 m, the sensor height will be calculated as the
sum of these two values: 6.02 m + 1.34 m = 7.36 m.
In this case, the sensor will report 6.02 m as the measured level and 1.34 m as the measured
relative level.
4.6. Units
Default measurement unit of the LX-80S is millimetres. It is possible to change the measurement
unit of the device using any of the aforementioned communication protocols. The following
measurement units are supported: millimetres, centimetres, metres, feet and inches. When
changing the unit of the device, special care must be taken when setting new parameter values to
the device as the device will now use the selected measurement unit for every measurement and
every measurement parameter.
4.7. Radar Calibration
The snow level sensor is able to perform self-calibration which calibrates the radar transceiver
electronics. Each instrument is calibrated in the factory, and the factory calibration parameters are
stored in the device. Typically, there is no need to repeat self-calibration, even after using the lsnow
evel meter over several years. In extremely rare cases, when troubleshooting the snow level sensor
that is not accurately measuring the snow depth, it is recommended to redo the self-calibration.
The self-calibration can be triggered by clicking on Recalibrate radar button which can be found in
the Settings view of the Geolux Instrument Congurator application.

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LX-80S Snow Level Sensor
5
Radar Settings
To change the radar settings, connect the snow level sensor to the PC computer, and start the
Geolux Instrument Congurator PC application. Through the user interface of the application, the
following parameters can be congured.
Communication Interfaces Parameters
Baud rate
1
0
010010 1 1 01
N bits per second
Band Rate
1 bit
RS-232 baud rate - Congures the baud rate (bits per second) for serial communication on RS-232
data line. This setting controls how many bits are sent on the communication line in one second. The
available values are standardised. Using higher baud rates over longer lines may introduce errors in
transferred data. The default instrument RS-232 baud rate is 115200 bps.
RS-485 baud rate - Congures the baud rate (bits per second) for serial communication on RS-485
data line. This setting controls how many bits are sent on the communication line in one second. The
available values are standardised. Using higher baud rates over longer lines may introduce errors in
transferred data. The default instrument RS-485 baud rate is 9600 bps.
RS-232 settings
Congures which parts of NMEA output is available over the interface. This setting is available on
devices with rmware versions above 2.3.9. By default the ags parameter is 0, which enables all
NMEA sentences. This parameter can be any of the following values:
0 - All NMEA sentences are sent over the interface
2 - $ANG NMEA sentence is not sent over the interface
Device ID
ID ID+1
ID
Device ID

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LX-80S Snow Level Sensor
Modbus ID - Congures the device (slave) ID to be used for Modbus RTU protocol. Modbus RTU uses
request/response format and allows multiple instruments to be connected on the same bus. When
a remote master transmits the request message, it will use the device ID as a device address. All
instruments will receive the request, but only the instrument with matching device ID will answer to
the received request.
SDI-12 ID - Congures the SDI-12 device ID to be used on SDI-12 interface. In SDI-12 request/
response protocol, this ID will be used to dene the instrument address, and the instrument will
respond only to requests with matching ID.
Modbus Parity
DATA
0
1
1 00 100X
Parily
PARITY
Parity is used in serial communication for basic error detection. When parity is set to None, no parity
is used, and no error detection is possible on bit level. When parity is set to Odd parity, an additional
bit is added to the communication that will be set to 1 when there is odd number of bits with value
1 in the 8-bit payload byte. Similarly, when parity is set to Even parity an additional bit is added
to the communication that will be set to 1 when there is even number of bits with value 1 in the
8-bit payload byte. Generally, all bytes on the receiver side where the parity bit is not matching the
message will be discarded. Default setting on most devices that use Modbus is even parity.
Modbus Stop Bits
DATA
0
1
100 100X X
Stop bit
STOP
BITS
DATA
0
1
1 0 0 100X
Stop bit
STOP
BITS
Stop bits are added to the end of each data byte transferred over serial communication, to allow
pause between two bytes. One or two bits may be used. The default setting on most Modbus RTU
devices is one stop bit, but some dataloggers may require that the instrument is congured to use
two stop bits.

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LX-80S Snow Level Sensor
4 – 20 mA Parameters
4 – 20 mA min. - To congure the 4 – 20 mA output range, the minimum measured value which
will correspond to 4 mA analog output needs to be set. The value is set in the currently congured
measurement unit. Example: if values measured by the instrument are expected to be within the range
of 700 mm to 5000 mm, it is recommended to congure the minimum value to slightly below 700 mm
(for example 500 mm). Alternatively, if the resolution is not critical, then minimum value for 4 – 20 mA
output can be left to the instrument minimum of 0 mm.
4 – 20 mA max. – To congure the 4 – 20 mA output range, the maximum measured value which
will correspond to 20 mA analog output needs to be set. The value is set in the currently congured
measurement unit. Example: if values measured by the instrument are expected to be within the range
of 700 mm to 5000 mm, it is recommended to congure the maximum value to slightly above 5000 mm
(for example 6000 mm). Alternatively, if the resolution is not critical, then maximum value for 4 – 20 mA
output can be left to the instrument maximum.
Processing Parameters
Filter Type
Changing the type of lter which is used to smoothen the measured data.
Nolter- No ltering is used and the raw measurements are reported.
IIR - Innite-Impulse Response lter is used to smooth the data. When compared to moving average
lter, IIR lter reacts more quickly to initial change in the data, but it takes longer for the smoothed value
to reach the new measurement. The use of IIR lter is discouraged for general applications. The IIR
constant can be congured separately.
Moving average - The moving average lter calculates the average value of a number of raw
measurements. The length for the moving average lter is congured separately through the Filter length
parameter.
Median - The median lter nds the median value from a number of raw measurements. The length for
the median lter is congured separately through Filter length parameter.
Standard deviation - This type of lter is similar to the moving average lter. It takes a number of raw
measurements (as dened by Filter length parameter), then removes 20% of outliers, and calculates the
average of the remaining 80% of values. This lter gives the best results.
Output value 4-20 mA
20 mA
4 mA
Min. Value Max. Value

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LX-80S Snow Level Sensor
Filter Length
Value
Average Filter length = 50
Filter length = 10
The length of the averaging lter, in number of readings, used to smooth the measured values. The
instrument performs 1 reading per second, so a lter length value of 10 will result in 10 seconds
integration time. When using longer lter lengths, more measured values are used for ltering, and the
resulting data will be smoother. However, when the snow depth changes, it will take more time for the
new measurement to be reported. Typically, this parameter should be set to a value between 10 and 50.
IIR Constant
Q = 0,9
Q = 0,4
Value
IIR
The constant used by innite impulse response (IIR) lter - if IIR lter is selected to be used instead of
average lter. Accepted values are decimal numbers between 0 and 1. When the IIR constant value is
closer to 0.0, the lter response will be slower. When the IIR constant value is closer to 1.0, then the lter
response will be faster.
Amplitude Threshold
Setting the minimum amplitude of the spectral peak in signal analysis algorithm required to detect
peak and report distance. If no peak above this value is detected, the sensor will report distance equal
to 0. The threshold is used to lter noise and false readings and it is recommended to keep this value
between 0 and 1000.

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LX-80S Snow Level Sensor
Peak Detector Type
Congures the type of algorithm which is used to detect the peaks in the radar echo curve. The
default setting should be Maximum peak. In specic cases, such as when the snow depth needs to be
measured, but there is a lot of vegetation protruding from the snow, Last peak detector type should be
used.
Measurement Parameters
Level Unit
The measurement unit used to report the measured snow level value. The default measurement unit is
millimetres. When changing the measurement unit, it’s important to make sure that other parameters
which depend on the measurement unit (such as active zone parameters) are also changed to the new
unit.
Level Offset
Changes the measurement level offset. This value should not be changed.
Active Zone Parameters
These parameters limits the operational range of the instrument. The instrument will detect snow level
only within the range set by the Active zone min. and Active zone max. parameters. These parameters
are the best way to lter unwanted radar reections from other structures and objects that are present
on the monitoring site, that could cause false instrument readings.
Active zone min. - It is strongly recommended to set the Active zone min. value to the minimum possible
distance between the snow and the instrument at the specic monitoring site.
Active zone max. - It is strongly recommended to set the Active zone max. value to the maximum
possible distance between the snow and the instrument at the specic monitoring site. Typically, this is
the distance between the instrument and the ground.