Operating instructions Electronic level sensor 11372800 / 00 02 / 2021 LW2720 GB
LW2720 Electronic level sensor Contents 1 Preliminary note . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Symbols used. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Warnings used . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4 4 2 Safety instructions . . . . . . . . . . . . . .
Electronic level sensor LW2720 10.1 Troubleshooting incorrect level readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.1 Level too high / too low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.2 Measured value is stuck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.3 Measured value drops when level close to antenna . . . . . . . . . . . . . . . . . . . . . . . .
LW2720 1 Electronic level sensor 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.
Electronic level sensor 2 • LW2720 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.
LW2720 3 Electronic level sensor 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.
Electronic level sensor LW2720 CIP process: The unit withstands standard CIP routines and SIP routines up to 140 °C. Optimisation of cleaning agent storage. GB 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.
LW2720 4 Electronic level sensor 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 5 LW2720 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).
LW2720 5.1.2 Electronic level sensor 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.
Electronic level sensor LW2720 A B 100% (20mA) I [mA] 20 1 4 2 C 0% (4mA) GB L AEP2 (ASP2) ASP2 (AEP2) D Fig. 2: Analogue output A: B: C: D: blind zone zone with reduced accuracy recommended measuring range zero point = reference point I: L: 1: 2: current level rising curve ([ASP2]<[AEP2]) dropping curve ([ASP2]>[AEP2]) Note the tolerances and accuracies during the evaluation of the analogue signal (Ò Data sheet). 5.3.
LW2720 Electronic level sensor L L SP1 SP1 HY SP2 t t no no nc nc Fig. 3: Single-point mode L: t: HY: Fig. 4: Two-point mode level time hysteresis Window function: u [SSC1 Config. Mode] must be set to [Window]. The width of the window can be set by means of the difference between [SSC1 Param. SP1] and [SSC1 Param. SP2] (Ò Fig. Window function). u [SSC1 Param. SP1] must be greater than [SSC1 Param. SP2]. The normally open or normally closed function is set by [SSC1 Config.
Electronic level sensor LW2720 unit continues to work in normal operation. If, however, it is not received again in sufficient strength within the delay time, the unit passes into the alert mode and output OUT2 changes into the defined state. In case of heavy foam build-up and turbulence, consider the option of creating a steady area. 5.3.4 GB Simulation function Various levels can be simulated for set-up, maintenance or interference reduction. The duration of the simulation can be selected (1 min...
LW2720 6 Electronic level sensor Mounting CAUTION With high process temperatures, parts of the unit may heat up. w Risk of burns u Do not touch the unit. u Protect the housing against contact with flammable substances and unintentional contact. u Allow the unit and process adapter to cool down before maintenance. Careful handling of the antenna u Be careful not to scratch or otherwise damage the antenna. Before installing and removing the unit: u Make sure that no pressure is applied to the system.
Electronic level sensor 6.2 LW2720 Inclination u Mount the unit vertically (90°) to ensure a good echo from the medium surface. u Maximum inclination (1): 3° (Fig. Inclination). GB 1 90° Fig. 7: Inclination 6.3 Non-metallic tanks Non-metallic tanks are, for example, fibreglass tanks. Nearby objects outside the tank may cause disturbing radar echoes as such materials may allow radar waves to pass through.
LW2720 6.5 Electronic level sensor Nozzle requirements u To allow the radar waves to propagate undisturbed, the specified nozzle dimensions should be observed (Ò Fig. Nozzle dimensions and table). u The inside of the nozzle must be smooth (i.e. avoid bad welding, rust, or deposit). Maximum nozzle height (H) as a function of the nozzle diameter (D): H Nozzle diameter (D) Nozzle height (H) 40 mm (1.5 in.) 150 mm (5.9 in.) 50 mm (2 in.) 200 mm (7.9 in.) 80 mm (3 in.) 300 mm (11.8 in.
Electronic level sensor LW2720 u To avoid dead space adhere to the dimensions: L < (D - d) d = 25 mm 1 L 2 GB d D 1: Leakage port 2: Seal 6.6.2 Notes on the use according to 3-A® u Make sure that the sensor is integrated into the system according to 3-A. u Use only adapters with 3-A qualification and marked with the 3-A symbol. Available accessories: www.ifm.com. The process connection must be provided with a leakage port. This is ensured when installed using adapters with 3-A approval.
LW2720 Electronic level sensor u Before installing, carefully remove the protective cap. u Be careful not to scratch or otherwise damage the antenna. 6.8.2 Place the O-ring, grease the thread The matching O-ring (EPDM) is supplied with the adapter. More O-rings are available as accessories. u Place the O-ring in the groove of the unit. u Lightly grease the thread of the unit with lubricating paste. The paste must be approved for the application and compatible with the elastomers used.
Electronic level sensor 6.8.3 LW2720 Premount the adapter for pipe fittings u Slide the coupling nut up over the bottom of the unit. GB u Make sure that the O-ring is mounted in the groove of the unit. u Screw the adapter onto the unit until it is hand-tight. u Secure the unit and adapter using a vice. Use suitable vice jaws (protectors). Do not over-tighten the vice as it might damage the adapter. u Tighten firmly. Recommended tightening torque: 35 Nm. Further tightening may affect the sealing.
LW2720 Electronic level sensor CAUTION During the welding operation, the adapter and the welding aid can increase in temperature to over 65 °C (149 °F). w Risk of burns u Let the components of the welding aid and weld-in adapter cool down before removal. u Hand-tighten the weld-in adapter on the welding aid. u Insert the clamping bolt through welding aid opening. u Mount the counter plate. 16 mm u Hand-tighten the nut.
Electronic level sensor LW2720 Welding operation: u During welding and the following cooling phase the unit must not be in place. u During welding, avoid overheating of the adapter and observe sufficient cooling phases. u While welding, the adapter must not warp. u The sealing edge of the adapter must not be damaged by weld spatter or similar. Ensure sufficient protection of the sealing edge before starting the welding process. GB u Fix the adapter in several spots with a sufficient adhesive force.
LW2720 Electronic level sensor u Lower the unit with the mounted Tri Clamp adapter onto the tank nozzle. u Tighten the clamp to the recommended torque (Ò Manufacturer’s installation instructions ). 6.9.2 Mount the unit with pipe fitting u Place a suitable gasket on top of the tank flange. u Lower the unit with the mounted adapter for pipe fittings onto the tank nozzle. u Tighten the coupling nut to the recommended torque (Ò Manufacturer’s installation instructions).
Electronic level sensor 6.9.3 LW2720 Mount the unit with VARIVENT® adapter u Make sure that the O-ring is mounted in the groove of the unit. u Screw the VARIVENT adapter onto the unit (not shown). Tighten to the recommended torque (Ò Installation instructions of the adapter). u Mount a suitable gasket at the bottom of the VARIVENT adapter. GB u Lower the unit with the mounted VARIVENT adapter onto the tank nozzle.
LW2720 Electronic level sensor u Remove the O-ring (1) from the unit before mounting. Otherwise, the O-ring may come off due to the missing end stop and enter the process. In this case, the seal is formed by the rear flat seal (2) (non-hygienic). 2 1 u Make sure that the rear flat seal (profiled sealing ring) is on the unit. u Screw the unit into the adapter. u Recommended tightening torque: 35 Nm.
Electronic level sensor 7 LW2720 Electrical connection The unit must be connected by a qualified electrician. The national and international regulations for the installation of electrical equipment must be adhered to. Supply voltage SELV, PELV according to the technical data sheet. GB u Disconnect power. u Connect the unit as follows: For marine applications (if approval available for the device), additional surge protection is required.
LW2720 8 Electronic level sensor Parameter setting Changing parameters during operation can influence the function of the plant. u Make sure that there will be no malfunctions or dangerous operation in your plant. The device parameters are set via the IO-Link interface. For this, an IO-Link master, IO-Link parameter setting software (Ò Accessories) and a suitable device description file (IODD) are required. u Always use the latest IODD: www.ifm.
Electronic level sensor LW2720 u Set the parameters. Before parameter setting, familiarise yourself with all the parameters. u Check if the unit has accepted the parameter settings. If necessary, read the unit again. u Check whether the unit operates correctly. GB 8.3 Adjustable parameters Parameters marked with “!” (in the “Access” column) (e.g. [SSC1 Param. SP2]) are only active if the assigned parameters have been selected.
LW2720 Electronic level sensor Parameter Options Explanation SSC1 Param. SP2 Setting range: 0...14.995 m Set point 2 for SSC1 (switching signal channel 1). Only available with window function and in twopoint mode. Access ! Set point 2 must be smaller than set point 1. If set point 2 is set higher than set point 1, this will be rejected by the device software. SSC1 Config. Logic [no] = normally open [nc] = normally closed Switching logic for SSC1 (switching signal channel 1).
Electronic level sensor LW2720 Parameter Options Explanation FOU2 [On] = analogue output switches to a value > 21 mA in alert mode. Switching output switches ON in alert mode. [OFF] = analogue output switches to a value < 3.6 mA in alert mode. Switching output switches OFF in alert mode. Response of OUT2 in alert mode. dAP Setting range: 0...600 s Damping of the measured signal (filter). S.Lvl Setting range: 0...10 m Level to be simulated in simulation mode.
LW2720 Electronic level sensor A: B: C: D: A device reference point (lower edge/sealing edge of the process connection) reference height (measuring range) zero point (lower end of the measuring range, tank bottom is lower) tank offset B C D + Fig. 15: Tank offset If the tank bottom does not correspond to the zero point: u Enter the distance between the zero point and the tank bottom (D) as [Tank offset]. • If the tank bottom is located lower than the desired zero point, as shown in Fig.
Electronic level sensor LW2720 m A B A: B: C: D: E: upper blind zone disturbing echo of object 100% (20 mA) of the analogue range detection threshold medium surface echo 3.0 C GB 2.5 2.0 D 1.5 E 1.0 0.5 0 0 150 300 450 600 750 900 mV Fig. 16: Upper blind zone / detection threshold Nozzles or other objects close to the antenna may cause disturbing reflections. Such reflections can be blocked out by configuring an upper blind zone (A).
LW2720 Electronic level sensor u Set the unit: (parameter [uni] = [m]). u Set the tank height: Parameter [Reference height] = [8.000] m. w The tank bottom may be interpreted as a low level. In this case: u Correct the tank height and configure a tank offset. u Define the upper blind zone: parameter [Upper blind zone] = [200] mm. w This setting is used to block out disturbing echoes from the nozzle. u Deactivate damping: parameter [dAP] = [0.0] s.
Electronic level sensor 9 LW2720 Operation 9.1 Function check After power-on the unit is in the operating mode. It carries out its measurement and evaluation functions and generates output signals according to the set parameters. GB u Check whether the unit operates correctly. After power-on (or after sudden changes in distance), the unit first adjusts itself to the level. This adjustment algorithm requires a certain amount of time and serves to ensure reliable measurements.
LW2720 Electronic level sensor Diagnostic message Possible cause Recommended actions No reflection signal No valid level reading. Reasons may be multiple: • Analyse echo peaks and check device configuration, especially the detection threshold. • No valid level echo in the measuring range. • Wrong device configuration. • Check physical installation of device (e.g. antenna contamination). • Consider increasing the [Alert mode delay time] parameter.
Electronic level sensor 10 10.1 LW2720 Troubleshooting Troubleshooting incorrect level readings GB 10.1.1 Level too high / too low A A: B: C: D: level time actual level measured level B C D Possible cause: • Incorrect tank geometry configuration. Recommended actions: • Verify the tank geometry parameters are configured correctly, especially the reference height. • Analyse the echo peaks and check the detection threshold. • Restore default settings and reconfigure the device. 10.1.
LW2720 Electronic level sensor Possible cause: • 15° Disturbing object in the tank. Recommended actions: • Analyse the echo peaks and check the detection threshold. • If possible, remove the disturbing object or change the device position. • Rotate the unit in steps of about 15 degrees. u After each step, check if impact of disturbing echoes is decreased by analysing the echo peaks.
Electronic level sensor LW2720 A A: B: C: D: level time actual level measured level GB B C D Possible cause: • The level is within the upper blind zone and a false echo is interpreted as the level. Recommended actions: • Check the setting of the upper blind zone. • Reduce the maximum permissible level, e.g. by adjusting the switch points. 10.1.4 Measured value fluctuates A A: B: C: level time actual level B C Possible cause: • Excessive foaming or turbulence.
LW2720 Electronic level sensor 10.1.5 Measured value is occasionally unstable A A: B: C: D: level time actual level measured level B C D Possible cause: • The level is close to a suppressed false echo. Recommended actions: • If possible, remove the disturbing object or change the device position. 10.1.6 Lagging of measured value during rapid level changes A A: B: C: D: B C D Possible cause: • Damping value (parameter [dAP]) is set too high.
Electronic level sensor LW2720 10.1.7 Measured value correct at 0% (4 mA) but incorrect at 100% (20 mA) A A: B: C: D: level time actual level measured level GB B C D Possible cause: • Analogue end point (parameter [AEP2]) is not set correctly. Recommended actions: • Correct parameter [AEP2]. 10.1.8 Incorrect measured value when level is above 50% A A: B: C: D: level time actual level measured level B C D Possible cause: • Strong multiple reflections are interpreted as the level.
LW2720 Electronic level sensor A A: B: C: D: level time actual level measured level B C D Possible cause: • A strong tank bottom echo is interpreted as the level. Recommended actions: • Verify the reference height is configured correctly. • With very low dielectric media: Reduce the reference height and configure a tank offset. 10.1.
Electronic level sensor LW2720 10.1.11 Alert mode when level close to tank bottom When the level is near the sloped tank bottom, the device enters the alert mode. A A: B: C: D: level time actual level measured level GB B C D Fig. 17: Possible cause: • Radar signal is scattered to the side by the sloped tank bottom. Recommended actions: • Verify the tank geometry parameters are configured correctly (especially the reference height and the tank offset).
LW2720 11 Electronic level sensor Maintenance, repair and disposal The unit can be unscrewed from the adapter for cleaning. u Check the unit and the mounting adapter at regular intervals and tighten again, if necessary. u Only use suitable tools with plastic wrench flats for wetted surfaces. u Clean the antenna (PTFE capsule) at regular intervals with appropriate agents to avoid contamination or formation of deposits in the long run.
Electronic level sensor 12 LW2720 Factory setting Parameter Factory setting Application Specific Tag *** Function Tag *** Location Tag *** uni m Reference height Initial value Tank offset 0 (m) Upper blind zone 0 (m) P-n PnP out1/out2 SSC1 / I (4…20 mA) dS1/dS2 0 (s) User setting Access GB dr1/dr2 0 (s) SSCx* Param. SP1 0.2 (m) ! SSCx* Param. SP2 0 (s) ! SSC* Confic. Logic no SSC* Confic. Mode Single point SSC* Confic. Hysteresis 0.05 (m) ! ASP2 0 (m) ! AEP2 0.
LW2720 13 13.1 Electronic level sensor Appendix Approvals and certificates The EU declaration of conformity, approvals and country-specific certificates are available at: www.ifm.
