FTS LX-80-8 User manual

EXTREME ENVIRONMENTS. EXTREMELY RELIABLE.
NON-CONTACT LEVEL METER
Continuous Level Measurement
Operating Manual
1.800.548.4264 | www.ftsinc.com
700-SDI-RADAR-LX-80-Man Rev 1 08 Oct 2021

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: http://support.ftsinc.com
Email: [e-mail]

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Contents
1.1 APPROPRIATE USE ..................................................................................................................................... 1
1.2 GENERAL SAFETY INSTRUCTIONS............................................................................................................ 1
2.1 CHANGING UNITS...................................................................................................................................... 2
2.2 RADAR CALIBRATION ................................................................................................................................ 3
2.3 FUNCTIONAL PRINCIPLE ........................................................................................................................... 3
2.3.1 MEASUREMENT THROUGH CONTAINERS ..................................................................................... 3
2.3.2 RAIN AND WIND ............................................................................................................................... 4
2.3.3 INTERFERENCE AND MULTIPLE RADARS ....................................................................................... 4
2.3.4 FOGGING AND EVAPORATION........................................................................................................ 4
2.3.5 REFLECTIONS .................................................................................................................................... 4
2.3.6 RELATIVE MEASUREMENT ............................................................................................................... 5
3.1CONNECTOR PIN-OUT AND WIRING ....................................................................................................... 7
3.2 SDI-12 INTERFACE...................................................................................................................................... 8
3.3 SERIAL RS-232 INTERFACE ........................................................................................................................ 8
3.4 SERIAL RS-484 INTERFACE ........................................................................................................................ 8
3.5 ANALOG 4-20 mA OUTPUT....................................................................................................................... 8
4.1 SITE SELECTION........................................................................................................................................ 10
4.2 INSTALLATION POSITION........................................................................................................................ 11
5.1 COMMUNICATION INTERFACES............................................................................................................. 12
5.1.1 BAUD RATE...................................................................................................................................... 12
5.1.2 DEVICE ID......................................................................................................................................... 12
5.1.3 MODBUS PARITY ............................................................................................................................ 13
5.1.4 MODBUS STOP BITS....................................................................................................................... 13
5.1.5 4-20 mA PARAMETERS ................................................................................................................... 14
5.2 PROCESSING PARAMETERS .................................................................................................................... 14
5.2.1 FILTER TYPE..................................................................................................................................... 14
5.2.2 FILTER LENGTH ............................................................................................................................... 15

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5.2.3 IIR (INFINITE IMPULSE RESPONSE) CONSTANT........................................................................... 16
5.2.4 AMPLITUDE THRESHOLD............................................................................................................... 16
5.2.5 PEAK DETECTOR TYPE.................................................................................................................... 16
5.3 MEASUREMENT PARAMETERS................................................................................................................ 16
5.3.1 LEVEL UNIT...................................................................................................................................... 16
5.3.2 LEVEL OFFSET.................................................................................................................................. 16
5.3.3 ACTIVE ZONE PARAMETERS .......................................................................................................... 17
5.3.4SENSOR HEIGHT ............................................................................................................................. 17
5.3.5 STAFF GAUGE.................................................................................................................................. 18
5.3.6 OPERATION MODE ......................................................................................................................... 18
5.3.7 POWER MANAGEMENT.................................................................................................................. 19
6.1 SERIAL RS-232 INTERFACE ...................................................................................................................... 20
6.2 SERIAL RS-485 INTERFACE ...................................................................................................................... 20
7.1 SDI-12 PROTOCOL ................................................................................................................................... 21
7.1.1 MEASUREMENT COMMANDS ....................................................................................................... 21
7.1.2 X COMMANDS................................................................................................................................. 22
7.2 NMEA PROTOCOL (RS-232)..................................................................................................................... 25
7.2.1 LEVEL MEASUREMENT REPORT .................................................................................................... 25
7.2.2 TILT ANGLE REPORT....................................................................................................................... 26
7.3 SERVICING PROTOCOL (RS-232)............................................................................................................. 26
7.3.1 CHANGE INTERFACE PARAMETERS: ............................................................................................. 26
7.3.2 CHANGE PROCESSING PARAMETERS:.......................................................................................... 28
7.3.3 CHANGE PROCESSING PARAMETERS:.......................................................................................... 29
7.4 MODBUS PROTOCOL (RS-485) ............................................................................................................... 32
7.4.1 MASTER REQUEST FORMAT .......................................................................................................... 32
7.4.2 SLAVE (SENSOR) RESPONSE FORMAT .......................................................................................... 32
7.4.3 RETRIEVING DATA FROM THE SENSOR........................................................................................ 33
7.4.4 WRITING TO THE DEVICE’S CONFIGURATION ............................................................................. 35
8.1 CONNECTING THE RADAR TO THE CONFIGURATOR........................................................................... 38
8.2 CONFIGURATOR FUNCTIONS................................................................................................................. 39
8.2.1 SETTINGS......................................................................................................................................... 39
8.2.2 ECHO CURVE ................................................................................................................................... 40

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10.1 SPECIFICATIONS....................................................................................................................................... 47
10.2 MECHANICAL ASSEMBLY ........................................................................................................................ 48

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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
The SDI-RADAR-LX-80 radar- based level sensor was developed specifically for continuous water
level monitoring in rivers, lakes and sea unlike other radar level sensors that were initially developed
for industrial applications and later adjusted to work in environmental monitoring applications. It
comes in three versions: 8 meter, 15 meter and 30 meter each with a 10m cable1. Measurement
frequency is 1 Hz.
FTS Part #
Model
Maximum Detection
Range
Accuracy
21216 LX-80-8 0.1M– 8.0M
(0.66 ft - 26.25 ft)
± 2mm
(± 0.08 in)
21217
LX-80-15
0.1M – 15M
(0.66 ft – 49.2 ft)
± 2mm
(± 0.08 in)
21218
LX-80-30
0.1M – 30M
(0.66 ft -98.43 ft)
± 2mm
(± 0.08 in)
The radar operates in the W-band (between 77 and 81 GHz), which provides high accuracy and
allows multiple radars to operate close to each other without mutual interference. Unlike
ultrasound level sensors, it is not affected by changes in air temperature and density.
The SDI-RADAR-LX80 is quickly and easily mounted to a pole above a water surface using the
supplied mounting bracket (part number 21135) and requires minimum maintenance once installed.
Mounting instructions are contained in Chapter 4.
For ease of reference, this manual shall refer to all models as the LX-80 throughout the document.
2.1 CHANGING UNITS
The following measurement units are supported:
•Millimeters
•Centimeters
•Meters
•Feet
•Inches
It is possible to change the measurement unit of the LX-80 using any of the supported
communication protocols. When changing the unit of measurement, special care must be taken to
ensure all related parameter values are also changed as the device will now use the selected
measurement unit for every measurement and every measurement parameter.
IMPORTANT: If measurement units are changed, other parameters which depend
on the measurement unit (such as active zone parameters) should also be changed
to the new unit
126.25 ft, 49.2 ft and 98.43 ft each with a 32.8 ft cable

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2.2 RADAR CALIBRATION
The level meter 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 level meter over
several years. In extremely rare cases, if a level meter is not accurately measuring the water level,
self-calibration may be required during troubleshooting. Self-calibration is conducted through the
Instrument Configurator application (refer to Chapter 8) by clicking on Calibrate radar button which
is visible in the Settings page of the application.
2.3 FUNCTIONAL PRINCIPLE
The LX-80 operates by transmitting a linear chirp in the frequency range between 77 GHz and 81
GHz and measuring the frequency shift of the electromagnetic wave reflected from the water’s
surface. The measured distance is proportional to the frequency difference between the
transmitted and received signal due to the Doppler Effect, converted into an appropriate output
signal and output as a measured distance. The modulation and detection process in the sensor
enables precise measurements which are not affected by air temperature, humidity, or other
environmental factors.
The distance measuring sensor in the instrument is designed to detect and eliminate obstacles from
the distance measurement signal spectrum. However, vibrations in the radar’s mounting position
can negatively impact this ability.
The radar beam utilizes an averaging effect over the beam’s surface footprint which assists in
reducing measurement errors caused by oscillations and undulation of the water’s surface. Slight to
moderate waves on the water’s surface will affect the measured signal level, usually seen as a
reduced SNR (Signal to Noise Ratio), but in most cases will not affect measurement accuracy.
However, if the measured surface is highly turbulent, the unpredictability of the water surface will
reduce accuracy. In that case, the length of the radar filter can be adjusted to filter out most, if not
all, the turbulence.
For best measurement results mount in accordance with directions given in Chapter 4.
2.3.1 MEASUREMENT THROUGH CONTAINERS
The LX-80 can be mounted outside of a container made of dielectric (non-conductive) materials to
measure the level of the liquid inside of the container. The radar’s microwave signals easily pass
through most dielectric (non-conductive) materials. Common Dielectric materials used in industry
and buildings such as ABS, PVC, Nylon, Teflon, Polycarbonate, Plexiglas, Polyamide, and
Polypropylene are very suitable for microwave level measurement from outside of the containers. In
such applications. The radar can be mounted above the container and pointed to the liquid inside
the container below the sensor, following the same mounting principles outlines in Chapter 4.

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2.3.2 RAIN AND WIND
The LX-80’s integrated internal software filters out effects of rain, fog and wind. However, these
filters have some limitations. The majority of measurement inaccuracies caused by environmental
factors can be solved by proper sensor installation (see Chapter 4).
Rain and snow fall reduce the reflectivity of the water surface thus reducing the SNR2. However, the
LX-80 is tested and calibrated to detect the surface even under heavy rainfall. For rain and snow
suppression, the most effective solution is to mount the radar so that it points directly at the surface
being measured.
Influence of the wind on the accuracy is negligible in most cases. The only exception is strong wind
as it will create surface waves and turbulence which can be detected as a shift in level. As mentioned
in Section 2.3, the length of the radar averaging filter can be increased so that it reports an average
measurement over a longer period of time to filter out turbulence.
2.3.3 INTERFERENCE AND MULTIPLE RADARS
The 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.
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.
2.3.4 FOGGING AND EVAPORATION
Generally, LX-80s are not affected by fog or evaporation. However, heavy evaporation with high
water density in the atmosphere can affect measurement accuracy.
The best solution in most cases is to increase the average period of the averaging filter 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.
2.3.5 REFLECTIONS
Water is very reflective medium for the radar waves and most of the power transmitted from the
radar transmitter will be reflected from the water surface. Reflections of the transmitted radar beam
follow the same physical laws as 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.
2Signal to noise ratio

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Depending on the surface roughness, the incident angle ratio between power reflected away from
the radar and towards the radar can significantly vary.
To maximize reflected power back to the radar, the radar should be mounted so that the angle of
the transmitted radar beam to the water is 90°. 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.
2.3.6 RELATIVE MEASUREMENT
Each sensor unit measures the distance between the sensor and the first detected object. For water
level measurement, it is preferred to report the actual water level from the bottom of the riverbed
to the surface of the water. That is why we offer relative measurement, which is calculated relative
to the mounted sensor height. Sensor height is defined as the distance from the mounted sensor
position to the bottom of the riverbed. This distance is a fixed value unique to every mounted unit. It
can be set to the device in two ways.
1) First is by setting the sensor height parameter directly using any of communication protocols
described in the following chapters. After setting the sensor height, relative measurement will be
calculated by the following formula:
=−
ℎ:
=  
= ℎℎ
=     .
For example: if the sensor is mounted 6.35m above the riverbed, and the measured distance
from sensor to the surface is 4.34m then the real water level is calculated as the difference
of these two values:
6.35m – 4.34m = 2.01m
In this case the sensor will report 4.34m as the measured level and 2.01m as the measured
relative level.
2) 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 the staff gauge height,
the following formula will be used to calculate sensor height:
=+
ℎ:
= ℎℎ
=     
=  .

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For example: the sensor is mounted at an unknown height above the riverbed and using
staff gauge it is determined that the water level at that given time is 1.34m. The sensor
detects water at the distance of 6.02m. By setting the value 1.34m as the staff gauge
measurement at the same time when the device measures the distance as 6.02m, sensor
height will be calculated as the sum of the two values:
6.02m + 1.34m = 7.36m
In this case the sensor will report 6.02m as the measured level and 1.34m as the measured
relative level.

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ELECTRICAL CONNECTIONS
3.1 CONNECTOR PIN-OUT AND WIRING
The LX-80 sensor is supplied with a robust IP68 M12 connector and cable. The connector and cable
details are shown on Figure 3-1. The user is responsible for connecting the sensor to the data
collection platform using the flying leads. Users can attach their own connector, connect the cable
via a terminal strip, or wire it directly to device electronics. Refer to Table 3-1 for wiring details.
Figure 3-1: M12 connector details
Table 3-1: Wiring Details
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 27 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
V+ Output power supply (=Vin) for supply of external optional
equipment and for use with analog 4-20mA output
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

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3.2 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.).
The device supports SDI-12 protocols version 1.3. The device is not an SDI-12 slave; however, it
responds to SDI-12 commands as expected from an SDI-12 slave. When operating the SDI-12
interface, low power mode is not supported: the radar works continuously (does not have
sleep/waking cycles).
3.3 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.
3.4 SERIAL RS-484 INTERFACE
Serial RS-485 interface is implemented as standard industrial half-duplex communication interface.
The most common communication protocol used with RS-485 interface is Modbus-RTU.
The communication interface is internally short-circuited, 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 the specifications of the receiving device.
3.5 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 connecting the LX-80 to PLCs,

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loggers, or data concentrators. The 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.
Figure 3-2: Analog 4-20 mA internal architecture
Measurement of the current by the client device (logger, PLC, modem etc.) must be implemented as
the high side current measurement as shown in figure 3-3. If a sensing resistor is used, resistance
should be selected from the range 10Ω to 500Ω, with a recommended value 100Ω for the sensing
resistor.
Figure 3-3: High side current measurement for the 4-20 mA analog output

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INSTALLATION
4.1 SITE SELECTION
For best results, the water’s surface being measured should be calm, clean of vegetation, rocks, sand
deposits or other obstacles. Additionally, the mounting location of the radar sensor should provide
an unobstructed line to the measured surface. Any close object in the vicinity of the sensor can
reduce accuracy and introduce offsets in measurements.
The radar beam is defined by a 3 dB width angle and covers a circular area on the water’s surface.
The size of the beam’s pattern on the water’s surface is dependent on the distance from the radar to
the water. Refer to Table 4-1 to determine the radar beam’s footprint and ensure it is free of
obstacles and other interfering factors previously listed.
The mounting location should be sturdy as vibrations of the mounting structure can affect the
radar’s algorithm ability to discard detected obstacles.
Table 4-1: Radar Height and Radar Beam Diameter at Surface
METRIC
IMPERIAL
Radar Height
above water
(m)
Radar Beam
Diameter at
Surface (m)
Radar Height
above water
(ft and in)
Radar Beam
Diameter
(ft and in)
0.3
0.03
11.8 in
1.18in
0.5
0.04
19.7 in
1.57 in
1
0.09
39.4 in
3.54 in
2
0.17
6 ft 6.7in
6.7 in
3
0.26
9 ft 10 in
10.24 in
4
0.35
13 ft 1.5 in
1 ft 1.78 in
5
0.44
16 ft 4.85 in
1 ft 5.32 in
6
0.52
19 ft 8.2 in
1 ft 8.5 in
7
0.61
22 ft 11.6 in
2 ft
8
0.70
26 ft 3 in
2 ft 3.56 in
9
0.79
29 ft 6.3 in
2 ft 7.1 in
10
0.87
32 ft 9.7 in
2 ft 10.25 in
11
0.96
36 ft 1 in
3 ft 1.8 in
12
1.05
39 ft 4.4 in
3 ft 5.34 in
13
1.14
42 ft 7.8 in
3 ft 8.88 in
14
1.22
45 ft 11.2 in
4 ft
15
1.31
49 ft 2.5 in
4 ft 3.58 in
20
1.75
65 ft 7.4 in
5 ft 8.9 in
25
2.18
82 ft 0.25 in
7 ft 1.83 in
30
2.62
98 ft 5.1 in
8 ft 7.15 in

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4.2 INSTALLATION POSITION
The level meter must be installed above the water surface at a 90° angle pointing directly towards
the water surface and at a height within the range specified in Table 4-2. Ideally the tilt angle should
be 0° along both the X and Y axes for a 90⁰ angle between the radar beam and the water surface.
However, the unit can tolerate up to ±2⁰ along either axis if the site does not allow for a 0° tilt angle.
During the installation a level should be used to confirm the unit’s position. Additionally, the tilt
angle can be determined by connecting the unit to a PC and checking the tilt angle in the Instrument
Configurator. Refer to Table 4-2 for recommended installation heights.
Figure 4-1: Installation Position
Table 4-2: Recommended installation heights
Min
Recommended
Max
Installation distance to
water surface
0.2m
(7.9 in)
>1m
(39.4 in)
Maximum measurement range of
the variant in use:
8, 10 or 30 m
(26.25, 49.2 or 98.43 ft)

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RADAR PARAMETERS
The following radar parameters can be configured by connecting the radar to a PC and using the
Instrument Configurator (refer to Chapter 8). Additionally, if using SDI-12 protocols, configuration
can be done through a datalogger and using the SDI-12 commands outlined in Chapter 12.
1) Communication interfaces
2) Processing parameters
3) Measurement Parameters
5.1 COMMUNICATION INTERFACES
5.1.1 BAUD RATE
Figure 5-1: Baud Rate
RS-232 baud rate: Configures the baud rate (bits per second) for serial communication on the
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 rate over longer lines
may introduce errors in transferred data. The default instrument RS-232 baud rate is
115200 bps.
RS-485 baud rate: Configures the baud rate (bits per second) for serial communication on the
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 rate over longer lines
may introduce errors in transferred data. The default instrument RS-485 baud rate is 9600
bps.
5.1.2 DEVICE ID
Figure 5-2: Device ID

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Modbus ID: Configures 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 the matching
device ID will answer to the received request.
SDI-12 ID: The SDI-12 device ID to be used on SDI-12 interface. In SDI-12 request/response protocol,
this ID will be used to define the instrument address, and the instrument will respond only
to requests with the matching ID.
5.1.3 MODBUS PARITY
Figure 5-3: Modbus Parity
Parity is used in serial communication for basic error detection. In general, all bytes on the receiver
side where the parity bit does not match the message will be discarded.
There are three parity options which can be selected:
None: No parity is used, and no error detection is possible on bit level.
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.
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.
The default setting on most devices that use Modbus is even parity.
5.1.4 MODBUS STOP BITS
Figure 5-4: Modbus Stop Bits

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Stop bits are added to the end of each data byte transferred over serial communication to allow a
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 configured to use
two stop bits.
5.1.5 4-20 mA PARAMETERS
Figure 5-5: 4-20 mA Parameters
4-20 mA min: To configure 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
configured measurement unit.
Example: If measured values are expected to fall within the range of 700 mm to 5000 mm,
it is recommended to configure the minimum value to slightly below 700 mm (for example
500 mm). Alternatively, if the resolution is not critical, then the minimum value for 4-20 mA
output can be left to the instrument minimum of 0 mm.
4-20 mA max: To configure 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
configured measurement unit.
Example: If measured values are expected to fall within the range of 700 mm to 5000 mm,
it is recommended to configure 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.
5.2 PROCESSING PARAMETERS
5.2.1 FILTER TYPE
Changes the type of filter which is used to smooth the measured data.
Note that not all firmware versions support all the Filter Types. Firmware versions and what they
support are listed at then end of this section.
No Filter: - No filtering is used and the raw measurements are reported.

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IIR (Infinite Impulse Response): This filter is used to smooth the data. When compared to a
moving average filter, the IIR filter reacts more quickly to initial changes in the data, but it
takes longer for the smoothed value to reach the new measurement. The use of the IIR filter
is discouraged for general applications. The IIR constant can be configured separately.
Moving Average: The moving average filter calculates the average value of a number of raw
measurements. The length for the moving average filter is configured separately through the
Filter Length parameter.
Median: The median filter finds the median value from a number of raw measurements. The length
for the median filter is configured separately through the Filter Length parameter.
Standard deviation: This type of filter is similar to the moving average filter. It takes a number of
raw measurements (as defined by the Filter Length parameter), removes 20% of outliers,
and calculates the average of the remaining 80% of values.
Devices with firmware versions up to 2.2.8. support only No filter, IIR and Moving average. In this
case, it is recommended to use the moving average filter.
Devices with firmware versions up to 2.3.2. support No filter, IIR, Moving average and Median. For
those devices it is recommended to use moving average or median filter.
Devices with firmware versions greater than 2.3.3. support all the filters listed above. The standard
deviation filter gives the best results.
5.2.2 FILTER LENGTH
Figure 5-6: Filter Length
The length of the averaging filter, in number of readings, used to smooth the measured values. The
LX-80 performs 1 reading per second, so a filter length value of 10 will result in 10 seconds
integration time. When using longer filter lengths, more measured values are used for filtering and
the resulting data will be smoother. However, when the water level 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. For highly turbulent water, a longer filter length is recommended.