IFM LW2720 User manual

Operating instructions
Electronic level sensor
LW2720
11372800 / 0002 / 2021
GB

LW2720 Electronic level sensor
2
Contents
1 Preliminary note.............................................................. 4
1.1 Symbols used........................................................... 4
1.2 Warnings used.......................................................... 4
2 Safety instructions............................................................ 5
3 Intended use ................................................................ 6
3.1 Application area......................................................... 6
3.1.1 Application examples.................................................. 6
3.2 Restriction of the application area ........................................... 7
4 Items supplied ............................................................... 8
5 Function.................................................................... 9
5.1 Measuring principle ...................................................... 9
5.1.1 Reflectivity, effect of dielectric constant. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1.2 Foam and turbulence.................................................. 10
5.1.3 Influence of vessel characteristics and installation . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.2 IO-Link................................................................ 10
5.3 Outputs ............................................................... 10
5.3.1 Analogue output ..................................................... 10
5.3.2 Switching function.................................................... 11
5.3.3 Defined state in the event of a fault (alert mode). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.3.4 Simulation function ................................................... 13
5.3.5 Damping function .................................................... 13
5.4 Output response in different operating states. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6 Mounting ................................................................... 14
6.1 Mounting position........................................................ 14
6.2 Inclination.............................................................. 15
6.3 Non-metallic tanks....................................................... 15
6.4 Beam angle and beam width............................................... 15
6.5 Nozzle requirements ..................................................... 16
6.6 Notes for hygienic applications.............................................. 16
6.6.1 Notes on the use according to EHEDG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.6.2 Notes on the use according to 3-A® . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.7 Mounting in a threaded connection .......................................... 17
6.8 Mounting preparations.................................................... 17
6.8.1 Remove the protective cap............................................. 17
6.8.2 Place the O-ring, grease the thread . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.8.3 Premount the adapter for pipe fittings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.8.4 Install the welding aid ................................................. 19
6.9 Mount the unit in the tank.................................................. 21
6.9.1 Mount the unit with Tri Clamp adapter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
6.9.2 Mount the unit with pipe fitting........................................... 22
6.9.3 Mount the unit with VARIVENT® adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.9.4 Install the weld-in adapter on the unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.9.5 Mount the unit with G1 connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7 Electrical connection .......................................................... 25
8 Parameter setting............................................................. 26
8.1 Parameter setting via PC and IO-Link master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.2 Parameter setting during operation .......................................... 26
8.3 Adjustable parameters.................................................... 27
8.4 System commands....................................................... 31
8.5 Example parameter setting ................................................ 31
9 Operation................................................................... 33
9.1 Function check.......................................................... 33
9.1.1 Detection quality check................................................ 33
9.2 Diagnostic messages, cause, troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
10 Troubleshooting.............................................................. 35

Electronic level sensor LW2720
3
10.1 Troubleshooting incorrect level readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
10.1.1 Level too high / too low................................................ 35
10.1.2 Measured value is stuck............................................... 35
10.1.3 Measured value drops when level close to antenna . . . . . . . . . . . . . . . . . . . . . . . . . . 36
10.1.4 Measured value fluctuates.............................................. 37
10.1.5 Measured value is occasionally unstable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
10.1.6 Lagging of measured value during rapid level changes . . . . . . . . . . . . . . . . . . . . . . . 38
10.1.7 Measured value correct at 0% (4mA) but incorrect at 100% (20mA) . . . . . . . . . . . . 39
10.1.8 Incorrect measured value when level is above 50% . . . . . . . . . . . . . . . . . . . . . . . . . . 39
10.1.9 Measured value drops to zero close to tank bottom . . . . . . . . . . . . . . . . . . . . . . . . . . 39
10.1.10 Level measurement is lost in an empty tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
10.1.11 Alert mode when level close to tank bottom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
11 Maintenance, repair and disposal ................................................ 42
12 Factory setting............................................................... 43
13 Appendix ................................................................... 44
13.1 Approvals and certificates ................................................. 44
GB

LW2720 Electronic level sensor
4
1 Preliminary note
You will find instructions, technical data, approvals and further information using the QR code on the
unit / packaging or at www.ifm.com.
1.1 Symbols used
Requirement
Instructions
Reaction, result
[...] Designation of keys, buttons or indications
Cross-reference
Important note
Non-compliance may result in malfunction or interference.
Information
Supplementary note
1.2 Warnings used
CAUTION
Warning of personal injury
wSlight reversible injuries may result.

Electronic level sensor LW2720
5
2 Safety instructions
• The unit described is a subcomponent for integration into a system.
– The system architect is responsible for the safety of the system.
– The system architect undertakes to perform a risk assessment and to create documentation in
accordance with legal and normative requirements to be provided to the operator and user of
the system. This documentation must contain all necessary information and safety instructions
for the operator, the user and, if applicable, for any service personnel authorised by the
architect of the system.
• Read this document before setting up the product and keep it during the entire service life.
• The product must be suitable for the corresponding applications and environmental conditions
without any restrictions.
• Only use the product for its intended purpose (Ò Intended use).
• Only use the product for permissible media (Ò Technical data).
• If the operating instructions or the technical data are not adhered to, personal injury and/or damage
to property may occur.
• The manufacturer assumes no liability or warranty for any consequences caused by tampering with
the product or incorrect use by the operator.
• Installation, electrical connection, set-up, operation and maintenance of the product must be
carried out by qualified personnel authorised by the machine operator.
• Protect units and cables against damage.
• The standards the unit complies with include TLPR and CISPR 11. Further standards and
specifications: Ò data sheet.
Radiated microwave energy:
The microwave energy radiated by the unit is much below that of mobile phones.
Maximum radiated energy: 2 mW.
According to the current state of science the operation of the unit can be classified to be
harmless to human health.
CAUTION
With high process temperatures, parts of the unit may heat up.
wRisk of burns
uDo not touch the unit.
uProtect the housing against contact with flammable substances and unintentional
contact.
uAllow the unit and process adapter to cool down before maintenance.
GB

LW2720 Electronic level sensor
6
3 Intended use
The unit continuously monitors the level of liquids in tanks without contact. Bulk materials are detected
depending on their properties (conical heaps, grain size, dielectric constant, etc.).
3.1 Application area
Non-contacting radar technology is ideally suited for food and beverage applications as it is
maintenance-free, has a top-down installation that reduces the risk of leakages, and is unaffected by
process conditions such as density, viscosity, temperature, pressure and pH.
The unit combines the innovative 80 GHz technology with the FMCW method and smart algorithms to
maximise measurement accuracy and reliability, even in small tanks and challenging fast-filling/ fast-
emptying vessels.
3.1.1 Application examples
Storage tank:
Provides insight into the tank and ensures production runs smoothly
without interruption.
Mixing tank:
Ensures correct filling and storage levels in tanks with agitators.
Batch filling:
Optimises the batch filling process.

Electronic level sensor LW2720
7
CIP process:
The unit withstands standard CIP routines and SIP routines up to
140°C.
Optimisation of cleaning agent storage.
3.2 Restriction of the application area
• The unit is not suitable for some bulk materials (e.g. coffee beans) due to their often very low
dielectric constant.
• Detection of bulk materials with a higher dielectric constant (e.g. grist due to its higher moisture
content) may be possible. See: Reflectivity, effect of dielectric constant (Ò/9)
uCheck the function by performing an application test.
• The unit is a TLPR device. TLPR (Tank Level Probing Radar) equipment are devices for level
measurement in a closed space only (i.e. metallic, reinforced concrete or fibreglass tanks, or
similar enclosure structures made of comparable attenuating material).
uInstallation must be carried out in accordance with the requirements of the following
standard: ETSI EN 302 372 (TLPR), Annex E
• Use preferably in metal tanks. When used in electrically non-conductive tanks (e.g. fibreglass
tanks):
– there may be deterioration caused by electromagnetic interference from other devices (noise
immunity according to EN 61326-1). Corrective measures: Non-metallic tanks (Ò/15)
– or if the mounting position is unfavourable, nearby objects outside the tank may cause
disturbing echoes.
Incorrect measurements may be caused by the following media:
• heavily foaming or turbulent surfaces.
• media which are very inhomogeneous, separate from each other thus forming separation layers
(e.g. oil layer on water).
uCheck the function by performing an application test.
uInstallation in a steady area.
wIn case of permanent signal loss, the unit generates an error message and switches the outputs to
a defined state.
GB

LW2720 Electronic level sensor
8
4 Items supplied
• LW2720 level sensor.
• Product information with safety instructions and reference to the complete operating instructions at
www.ifm.com.
In addition, the following is necessary for installation and operation:
• Mounting material (Ò Accessories)
Only use accessories from ifm electronic gmbh! The optimum function is not ensured when
using components from other manufacturers.
Available accessories: www.ifm.com.

Electronic level sensor LW2720
9
5 Function
5.1 Measuring principle
The measuring principle of the unit is Frequency Modulated Continuous Wave (FMCW). The unit
continuously emits electromagnetic waves in the GHz range with a constantly varying frequency
towards the medium surface. Since the transmitter continuously changes the frequency of the
transmitted signal, there will be a difference in frequency between the transmitted and the reflected
signals (Ò Fig. Measuring principle). The frequency of the reflected signal is subtracted from the
frequency of the signal transmitted at that moment, resulting in a low frequency signal which is
proportional to the distance to the medium surface. This signal is further processed to obtain fast,
reliable, and highly accurate level measurements.
d
fin
fmax
fmin
fout
fin fout
t
f
A
C
D
B
Fig.1: Measuring principle
Δf ~ d = distance
A: frequency (GHz)
B: time (s)
C: transmitted signal
D: reflected signal
Due to the 80GHz technology used, the unit generates a very focused signal beam (beam angle
approx. 10°). This extends the range of possible applications and enables installation even in small
tanks and confined spaces (e.g. in tanks with agitators, heating coils, etc.).
5.1.1 Reflectivity, effect of dielectric constant
The reflectivity of the medium has a substantial effect on the reflected signal (echo amplitude). The
reflectivity is directly dependent on the dielectric constant of the medium. A high dielectric constant
provides better reflectivity, thus improving the performance of the level measurement. This also
indirectly affects the maximum achievable level measuring range. Minimum dielectric constant: Ò
Data sheet
Dielectric constant (also: relative permittivity) of some media
Air (reference quantity) 1
Water ≈ 80
Salt water ≈ 32
Water, demineralised ≈ 30
Beer brew ≈ 25
Vinegar ≈ 24
Maize starch ≈ 18
Coarse soya flour, 19% moisture ≈ 18
Coarse soya flour, dry (application test recommended) ≈ 3
Vegetable oil (application test recommended) ≈ 2…4
Grist (application test recommended) ≈ 2…3
Malt (application test recommended) ≈ 2…3
Skimmed milk powder (application test recommended) ≈ 2
Palm oil (not detected reliably) ≈ 1.8
Coffee beans (not detected reliably) ≈ 1.5
GB

LW2720 Electronic level sensor
10
5.1.2 Foam and turbulence
Foaming liquids or turbulence may cause weak and varying echo amplitudes. Surface turbulence is
not normally a problem unless it is excessive.
Measurement in foamy applications depends largely on the foam properties. If the foam is light and
airy, the actual level is measured. For heavy and dense foam, the unit may measure the level of the
foam’s upper surface.
5.1.3 Influence of vessel characteristics and installation
The unit should be mounted so that objects such as heating coils, ladders and agitators are not in the
radar signal path. These objects may cause false echoes which can affect the measurement and lead
to measurement errors. However, the unit has built-in functions designed to reduce the influence from
disturbing objects where such objects cannot be totally avoided. Vertical and inclined structures cause
minimal effect since the radar signal is scattered rather than directed back to the antenna.
5.2 IO-Link
The unit has an IO-Link communication interface which requires an IO-Link capable module (IO-Link
master).
The IO-Link interface enables direct access to the process and diagnostic data and provides the
possibility to set the parameters of the unit during operation.
In addition, communication is possible via a point-to-point connection with a USB IO-Link master.
The IODDs necessary for the configuration of the unit, detailed information about process data
structure, diagnostic information, parameter addresses and the necessary information about the
required IO-Link hardware and software can be found at www.ifm.com.
5.3 Outputs
The unit generates output signals according to the parameter setting. Two outputs are available:
• OUT1: switching output / IO-Link
• OUT2: analogue output 4...20 mA or switching output (configurable)
5.3.1 Analogue output
The unit provides an analogue signal proportional to the level (according to NAMUR NE43, DIN IEC
60381-1) or a switching signal on output OUT2. The analogue output can be configured.
• Parameter [ou2] = [I] sets output OUT2 as analogue output.
• Parameter [ASP2] sets at which measured value 4mA are provided.
• Parameter [AEP2] sets at which measured value 20mA are provided.
• If [ASP2] is set lower than [AEP2], a rising curve results; if [ASP2] is set higher than [AEP2], a
dropping curve results (Ò Fig. Analogue output).
Minimum distance between [ASP2] and [AEP2] = 20 % of the active zone