This circular airflow measurement unit is available in many sizes. Accurate measurement based on differential pressure created by measurement probe pipes.
|Measurement probe pipes||Aluminium|
|Measurement tubes||PVC and PP plastic|
|Duct gaskets||1C-polyurethane hybrid|
Airflow in a duct creates a pressure difference between the front and rear probes.
The corresponding airflow rate can be defined by measuring the pressure difference sensed by the two crossing sets of averaging probes.
In order to ensure the accuracy of the airflow measurement the safety distances between the measurement unit and flow disturbances (e.g. bends, T-branches) have to be respected. The necessary safety distances before and after different disturbances are presented in figures below.
The figure below describes also the recommended axial orientation of measurement probes related to bends and T-branches.
Connect the measurement tubes to the manometer and read the pressure difference. The airflow rate is calculated using the formula below or by reading the airflow rate directly from the diagram:
With model Halton MSD, MU=B airflow can be defined using integrated airflow control unit (VRD3). The actual measured airflow rate (qv) can be defined by the controller feedback signal (U5) and air flow measurement unit’s nominal airflow (qv_nom).
|Signal||Formula||Controller type and mode||Terminals
|0…10 VDC||qv = qv_nom*U5 / 10||MSD, MU=B
|qv = qv_nom*(U5-2) / 8||MSD, MU=B
Nominal airflow rates of Halton MSD are presented in the table below:
|100||70 l/s (252 m3/h)|
|125||115 l/s (414 m3/h)|
|160||210 l/s (756 m3/h)|
|200||340 l/s (1224 m3/h)|
|250||538 l/s (1937 m3/h)|
|315||885 l/s (3186 m3/h)|
|400||1555 l/s (5598 m3/h)|
|500||2449 l/s (8816 m3/h)|
1 (-) 24 VAC/DC system neutral
2 (+) 24 VAC/DC live
5 (U5) 0…10 / 2…10 VDC actual volumetric flow (
switchable with ZTH-VAV, 0…100 % Vnom)
Airflow control unit (VRD3)
The casing of the measurement unit shall be made of galvanised steel.
The measurement probe pipes shall be made of aluminium.
The measurement unit shall have integral gaskets.
D = Size of duct connection (mm)
100, 125, 160, 200, 250, 315, 400, 500
MU = Electronic control unit
NA Not assigned
B Electronic airflow control unit (VRD3)
PT = Difference Pressure transmitter
NA Not assigned
ZT = Tailored product
Y Yes (ETO)
MSD-160, MU=NA, ZT=N