Quick start
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© 2016 Van Putten Instruments BV | MAN-VP-SMPR-UK | Revision:1600 | Date:23-03-2016
5
Measurement
For all parameters the update interval is 1 second. Within this second, multiple samples are taken
and averaged to provide a stable and reliable output.
5.1
Flow
The VPSensorCartridge uses our proprietary insertion type thermal mass flow sensor. There is no
bypass flow, which results in a high robustness and less sensitivity for dirt or particles. The flow
sensor is directly temperature compensated. The flow reading is under normalized conditions (DIN
1343).
The sensor response signal is directly related to
the mass flow rate and can be described by the
following formula:
Vout = k *λ* ρ * v * (Ts-Tg)
Vout = output voltage
k = sensor (geometrical) constant
λ = thermal conductivity of the gas
ρ = density of the gas
v = actual velocity in m / sec
Ts = sensor temperature
Tg = gas temperature
The optional bi-directional sensitivity is shown in
the picture on the right. In bi-directional mode the
negative flow value will show up as a minus sign.
The 4..20 mA value needs to be adapted to suit
the application.
for
details.
5.2
Pressure
The VPSensorCartridge features a built-in gauge pressure sensor. The range of the pressure sensor
can vary per VPSensorCartridge type. Check specifications for details. The sensor membrane can
handle media which are compatible with glass, silicon, stainless steel, Sn/Ni, plating and An/Ag
solder.
5.3
Temperature
The built in temperature sensor measures the compressed air / gas temperature.
At low flow rates between zero flow and 10 m/sec, the temperature sensor may heat up at zero flow
conditions, due to the heated flow sensor element.
Temperature compensation effects: The flow sensor is compensated dynamically for changes in gas
temperature. When exposed to quick temperature changes or large temperature changes (for
example taking the unit from outdoor to indoor during winter time, or when mounted downstream of a
heat regenerated drier) the temperature compensation may lag behind, which may result in
significant measurement errors.