D-FL 220

Volume flow measuring system

Ultrasonic sensor system to measure the velocity and the volume flow of flue gas or process gas in pipes or ducts. Two identical sensors transmit and receive ultrasonic pulses alternately. The flow velocity of the flue gas is precisely calculated from the direction dependant transit time difference of the ultrasonic pulses. The flow rate is calculated taking into account the cross-section of the stack, the gas temperature and the absolute pressure. The D-FL 220 system performs automatic self-check cycles and requires extremely low maintenance.


  • In situ measurement, continuous measurement
  • Measurement even in wet or dust-laden flue gas
  • Allows calibration to measure the volume flow
  • Suitable for thick-walled stone / insulated ducts
  • Automatic zero and span check
  • Sensors are purged and are therfore not in contact with sample gas
  • Easy installation, adjustment and maintenance
  • No separate control unit required
  • Very low maintenance


Suitable for velocity and volume flow measurement

  • at incinerators in general
  • at garbage, hazardous waste and sewage sludge incinerators
  • at facilities for cement production
  • at power stations with gas, oil, coal or co-firing
  • at installations for the incineration of biomass

Technical Data

Sample gas typeAir, flue gas, non flammable process gas
Sample gas temperature-20…300 °C (-4…392 °F) standard, other on request
Inner duct pressure-50...+20 hPa (optional higher)
Sample gas relative humidity0…100 % RF, condensation allowed
Sample gas flow velocity0…40 m/s
Stack/duct inner diameter0.5…13 m (1.6…42.7 ft)
Measuring principleMeasurement of direction-dependent transition times of ultrasonic pulses, thereof calculation of flow speed and volume flow.
13., 17., 27., 30. BImschV
TA Luft
EN 14181
EN 15267-1, -2, -3
DIN EN 16911-2
40 CFR 60 US EPA PS6
CertificatesCE, QAL1 DIN EN 14181 / DIN EN ISO 14956 / DIN EN 15267-3, MCERTS, EAC
Measuring locationIn-situ, non-contact. Mounted at stack, measurement across the stack, purged sensors are not in contact with flue gas.
Measuring path length1…15 m
Measuring angle45° ±15° relative to the flow direction
Self-check, protective functionsAutomatic internal self-test
Automatic zero- and span check
System componentsD-FL 220 MK measuring head transmitter
D-FL 220 MK messuring head receiver
D-FL 220 SPF purge flange
D-FL 220 E mounting pipe with flange (option)
D-ISC 100 universal operating unit (option)
D-TB 100 terminal box (option)
D-BL pure air unit (option)
Physical measuring valueDirection-dependent transition time of ultrasonic pulses
Derived measuring valuesFlow velocity, volume flow at operating conditions or normalized
Measuring range gas velocity0…40 m/s
Output range gas velocityFreely programmable
Measuring range volume flow0…5000000 Nm3/h
Output range volume flowFreely programmable
Measuring range temperature0…400 °C
Output range temperatureFreely programmable
Resolution0.1 m/s
Lowest detection limitmax. 0.3 % of the measuring range
Zero point driftmax. 0.3 % of the measuring range / month
Span driftmax. 0.2 % of the measuring range / month
Combined standard uncertainty
acc. to QAL1, DIN EN 14181
0.33 m/s
Integration time1…180 s, freely programmable
Process connectionD-FL 220 E mounting tube with flange, DN80 PN6, tube ID = 100 mm
Digital interfacesRS 485 Modbus RTU, bi-directional communication, USB (Service)
Analog outputs1x 4-20 mA, 400 Ohm, isolated, assignment parameterisable
Digital outputs2 x contact NC/NO, permissible load 60 VDC / 30 VAC / 0.5 A, function can be assigned. Typically: maintenance, failure
Power supplySensor supply voltage 24 VDC ±10 %, 0.5 A
Ambient temperature (operational)-40…+70 °C (-40…158 °F), optional higher
IP protection class (IEC 60529)IP65
Dimensions (HxWxD)Measuring head housing: 113 x 84 x 188 mm (190 x 190 x 330 mm with purge air flange)
Measuring probe (DxL): 110 x 230…2270 mm, other on request
Weight6.5 kg (sensor head 610 mm with purge air flange, weight depending on version)
MaterialHousing: Polyamide, RAL 5017,
Ultrasonic transducer: PA6.6, PBT, FRP, both fire class B1 (UL 94 V0),
Process parts: Stainless steel 1.4571 (316 Ti)
Mechanical interfacesPurge air connector OD = 40 mm
Air supply capacity10…40 m3/h (per measuring head)
Process connectionDN80 PN6
Ambient temperature (operational)-20…+50 °C (-4…122 °F), optional higher
Dimensions (HxWxD)190 x 200 x 90 mm
Weight2.9 kg
MaterialStainless steel 1.4571 (316 Ti)
Process connectionDN80 PN6
Dimensions (HxWxD)108 x 335...2135 mm, other on request
Weight5.5 kg (L = 335 mm, depending on version)
MaterialStainless steel 1.4571 (316 Ti)
GFK (Durabest 180)
Power supply90 - 264 VAC, 48 - 62 Hz, other on request
Power consumption30 W
Ambient temperature (operational)-25…+55 °C (-13…131 °F), optional higher
IP protection class (IEC 60529)IP65
Dimensions (HxWxD)160 x 160 x 110 mm
Weight1.5 kg
MaterialPolycarbonate, RAL 7035, fire class: B1 (UL 94 V0)
Mechanical interfaces2x purge air connector OD = 40 mm
Power supply115 / 230 VAC, 50 / 60 Hz, other on request
Power consumption0.37 kW (50 Hz) / 0.43 kW (60 Hz)
Air supply capacity40 m3/h (50 hPa) / 60 m3/h (25 hPa), other on request
Ambient temperature (operational)-20…+50 °C (-4…122 °F), other on request
IP protection class (IEC 60529)IP55
Dimensions (HxWxD)480 x 450 x 320 mm
Weight12 kg
MaterialStainless steel 1.4301
Mechanical interfaces1x Mini-USB
1x DURAG device connector M23 (option)
Digital interfaces1x USB (service)
1x DURAG Modbus
1x Modbus RTU / RS-485 (optional extension module)
1x Profibus DP (optional DIN rail converter)
1x Modbus TCP (optional software module)
Analogue outputs1x 4...20 mA, 400 Ohm, isolated, assignment programmable
up to 17x with extension modules (option)
Analogue inputsNone (standard)
16x with extension modules (option) 0…20 mA, 50 Ohm, zero point programmable
Digital outputs3x relais output, contact NC/NO, permissible load 48 V, 0,5 A potential free, assignment programmable
up to 35x by extension modules (option)
Digital inputs1x digital input (standard), potencial free, assignment programmable
up to 33x by extension modules (option)
Power supply90...264 VAC, 48...62 Hz, 200 VA
Display, status LEDsGraphical LC display 120 x 92 mm,
5 LEDs for status display
Service software D‑ESI 100, including remote access via web-interface (option), requires PC with Windows XP® or Windows 7® OS
Remote access via USB / Modbus RTU (option) / Modbus TCP (option)
Ambient temperature (operational)-20 ... +50 °C (-4 ... 122 °F)
-40 ... +60 °C (-40 ... 140 °F) (option)
IP protection class (IEC 60529)IP65
Relative ambient humidity≤ 95% RF, non-condensing. Use weather protection hood for ≥ 95% RF
Altitude≤ 2000 m
EX zoneZone 2 (option)
Dimensions (hxwxd)220 x 335 x 145 mm
286 x 335 x 145 mm (incl. cable glands)
Weightapprox. 5 kg
MaterialStainless steel 1.4301, painted blue RAL 5017
  • The suitability of the D-FL 220 for the listed ranges, especially the max. measuring length depends on the sample gas temperature, the dust type and it's size distribution.
  • Subject to technical modifications.



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