Testo - Flow Straightener

Flow Straightener - creates a correction of the swirl into a parallel flow from air conditioning outlets.
Part number: 0554 4172
Manufacturer: Testo
£69.00 (ex VAT)

Testo is the only manufacturer to offer a solution for swirl outlets: the flow straightener (0554 4172)

Temperature range 0 - 50°C
Measuring range 0.1 … 200 m³/h, preferred 0.1 … 100 m³/h
Material PA66+30%GF
Dimensions (instrument) 370 x 190 x 210 mm
Weight 0.554 kg

Testo Calibration Services avaliable - Call 01420 566845 or email 

  • Vane anemometers from 12mm to 100mm diameter in range 0.3 to 30m/s
  • Thermal anemometers (Hot bulb/Hot wire) in the range 0.1 to 20m/s
  • Uncertainties of measurement as follows:

0.1 m/s to 0.2 m/s, ±0.56 %

0.2 m/s to 0.6 m/s, ±0.52 %

0.6 m/s to 1 m/s, ±0.32 %

1 m/s to 15 m/s, ±0.45 %

15 m/s to 20 m/s, ±0.69 %

20 m/s to 30 m/s, ±0.87%

Why is the flow straightener necessary?

The funnel set testovent 417 in combination with, for example, the testo 417 is designed for the measurement on ventilation grilles and disc outlets. However, if the flow rate is measured at swirl outlets the swirl will influence the rotation of the vane anemometer. In general there are two different two scenarios:

(1) The vane probe will rotate at a higher speed if the air blown into the room swirls in the same direction as the rotation of the vane probe.

(2) The vane prone will rotate at a lower speed if the air blown into the room swirls in the opposite direction of the vane’s rotation.
In both scenarios the swirl will increase the measurement uncertainty: The volume flow is either displayed to high (1) or to low (2). For details see the enclosed presentation.

Swirl outlets have become more popular with air conditioning systems down to their advantages-

Advantages of Swirl Outlets:

  • Supplying the conditioned air without drafts and turbulences
  • Quick adjustment of the supplied air temperature to the indoor air
  • high-quality indoor air flow
  • specially designed for comfort rooms like at single-family houses, office buildings,
  • schools, recreation rooms or hospitals
  • low-noise operation


Operation of the flow straightener

The flow straightener will be connected between the funnel hood (0563 4170) and the testo 417 (0560 4170 ). The flow straightener enables a modification of the swirled flow into a straightened flow, which allows a reliable measurement of the flow rate by means of the testo 417. Currently none of our competitors can offer a similar solution.

Advantages of the flow straightener

- More accurate volume flow measurement independent of the swirl direction.
- Reliable measurement results on swirl outlets.
- System compatibility with the 100mm vane probes of the testo 435 (0635 9435), 400/445 (0635 9340) and 480 (0635 9343).
- A patent application has been lodged.
- Available as an optional accessories (0554 4172) or as a set.

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