Transit Time Ultrasonic Flowmeter

EESIFLO Sonalok 7S

The EESIFLO Sonalok 7SZ range of non-invasive flowmeters utilises ultrasonic technology for the accurate flow measurement of liquids in full pipes. The field mounted flow transmitter can be configured via the keypad without any additional programming devices and is available as single channel unit. The measurement of flow is based on the principle that sound waves are influenced by a flowing medium.

Measurements are made by penetrating the pipe with ultrasound and subsequently time differences, frequency variations and phase shifts of the ultrasonic signals are evaluated. This measuring technique has no effect on the flowing liquid. There is no pressure loss in the pipe and no wear on components of the measuring device.

The ultrasonic sensors are clamped onto the outside of the pipe, thus eliminating the need to dismantle the pipework and interrupt the process. The EESIFLO Sonalok 7SZ can be applied to any type of standard pipe carrying clean or dirty liquids.


  • Ultrasonic flowmeter in IP 66 wall mounted enclosure
  • Easy to install clamp-on sensors with no process interruption
  • Non-invasive flow measurement of liquids, no pipeline disturbance, no pressure loss
  • Suitable for all commonly used pipe materials with pipe diameters from 10 mm to 2.5 m (1/2″ to 100″)


  • Low installation effort and costs
  • Measurement is independent of fluid conductivity and pressure
  • No pressure loss, no possibility of leakage
  • Retrospective installation for existing plants possible
  • No cutting of pipes necessary, no interruption of process, no plant shut down
  • No additional fittings for maintenance required
  • Hygienic measurement, no risk of contamination, suitable for ultra clean liquids
  • No contact with medium, no risk of corrosion when used with aggressive media
  • Cost advantages when used with large diameter pipes, high pressure systems, etc.
  • Low stocking costs, nearly all pipe sizes are covered with only 2 types of sensors



Measuring principle       Ultrasonic time difference correlation principle
Flow velocity range0.01 … 25 m/s
Resolution0.025 cm/s
Repeatibility0.15 % of measured value ± 0.01 m/s

Volume flow

± 1 … 3 % of measured value depending on application,
± 0.5 % of measured value with
process calibration
Flow velocity
± 0.5 % of measured value

Turn down ratio1/100
Gaseous and solid content of medium< 10 % of volume

Flow transmitter

Enclosure      Wall mounted housing
Degree of protectionIP 66 according EN 60529
Operating temperature-10 … 60 °C (14 … 140 °F)
Housing materialAluminium, powder coated
Flow channels1
Power supply100 … 240 V AC or 18 … 36 V DC, specials upon request
Display2 x 16 digit LCD, dot matrix, backlit
Dimensions H 140 x W 190 x D 70 mm without cable glands
WeightApprox. 1.5 kg
Power consumption< 10 W
Signal damping0 … 100 s, adjustable
Response time1 s
Measuring cycle100 … 1000 Hz, single channel
Operating languagesSelectable between Danish, English, German, French, Dutch, Norwegian, Polish, Czech, Turkish, Spanish

Quantity and units of measurement

Volumetric flow rate    m3/h, m3/min, m3/s, l/h, l/min, l/s, USgph (US gallons per hour), USgpm, USgps, bbl/d (barrels per day), bbl/min, bbl/s
Flow velocity  m/s, inch/s
Mass flow rate  g/s, t/h, kg/h, kg/min
Volume  m3, l, gal (US gallons), bbl
Massg, kg, t


Serial interfaceRS 485 optional
Process outputsGalvanically isolated from main electronics
Current0/4 … 20 mA active (Rext < 500 ohm), 0.1 % of measued value ± 15 microAmp
Digital (pulse, status)Totaliser value 0.01 … 1000 / unit, width 80 … 1000 ms, Open-Collector 24 V/4 mA

Large pipe transducers

Diameter range50 … 2500 mm
Dimensions 60 x 30 x 34 mm
Material Stainless steel
Temperature range  -30 … 80 °C (-22 … 176 °F) or
-30 … 130 °C (-22 … 266 °F),
higher temperatures upon request
Degree of protection IP 65 acc. EN 60529, IP 67 or 68 optional
Cable lengths10 m, 20 m, 50 m, special

Small pipe transducers

Diameter range    10 … 250 mm
Dimensions 43 x 18 x 22 mm
MaterialStainless steel
Temperature range-30 … 80 °C (-22 … 176 °F) or
-30 … 130 °C (-22 … 266 °F),
higher temperatures upon request
Degree of protectionIP 65 acc. EN 60529, IP 67 or 68 optional
Cable lengths10 m, 20 m, 50 m, special

Uncertainty specification

EESIFLO Sonalok 7SZ Ultrasonic Flowmeters


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