D-LX 720

Compact flame monitor with fibre optic system


  • Wide sensitivity range
  • For ambient temperatures from -40°C up to +85°C
  • Dual channel design throughout
  • Measurement of flame flicker frequency
  • Selective to individual burners and fuels
  • Optionally with complete SIL3 certification
  • Available with cable gland, cable plug (version /MP) or as version for hazardous areas


  • Burners with difficult installation conditions for conventional flame sensors or on those whose ambient temperature near the sighting tube is too high
  • Power stations
  • Chemical industry
  • Refineries
  • Cement plants
  • Waste incinerators
  • Steam generators
  • Heating plants

Technical Data

Operational modeIntermittent operation and continuous operation
SafetySelf-monitoring and fail-safe
Auxiliary supply24 VDC
Flame relay1x NO contact, 24 VDC, 0.5 A
Status relay1x NO contact, 24 VDC, 0.5 A
Flame Failure Detection Time (FFDT)1, 2, 3, 5 s
Analogue output0/4...20 mA
Spectral rangesUV, IR
Threshold switchesFlame intensity and flicker frequency
CommunicationLED, Modbus RTU, IrDA
Ambient temperature range-40...+85°C
Protection classIP66/68
IP65 for version /MP
Dimensions85 x 85 mm, length approx. 175 mm
Weightapprox. 1.25 kg
Ex protection
D-LX 720 ../84ExII 2G Ex d IIC T6 or T5 Gb
II 2D Ex tb IIIC T85°C or T100°C Db
D-LX 720 ../85ExCl. I, Div. 1, Gr. A, B, C, D T6/T5
Cl. II, Div. 1, Gr. E, F, G T6/T5; Class III
Type 4
Hazardous locations: indoor/outdoor
D-LX 720 ../86ExCl. I, Div. 2, Gr. A, B, C, D T6/T4
Cl. II, Div. 2, Gr. E, F, G T6/T4; Class III
Type 4
Hazardous locations: indoor/outdoor
D-LX 720 ../87ExII 3G Ex nAnC IIC T6 or T4 Gc
II 3D Ex tc IIIC T85°C or T135°C Dc
Max. ambient temperature+85°C (/84Ex, /85Ex)
+65°C (/86Ex, /87Ex)
Protection classIP66
DimensionsØ120 mm, length approx. 230 mm
Weightapprox. 3.2 kg


  • LED bar graph display for the flame intensity (D-ZS 129)
  • Terminal box for connecting the flame monitor (D-ZS 140-12)
  • Installation flange for D-LL 703 fibre optic system (D-ZS 703)
  • Welding flange for D-LL 704 fibre optic system (D-ZS 704)
  • Wide range power supply unit for supply of several D‑LX 720 (D-NG 24/25a)
  • D-LX 200 Test kit for software supported tests of the compact flame monitors D-LX 200/720

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