D6F-series MEMS Flaw Sensor User’s Manual (A286) 14
6.3.4 Consideration of the laminar flow
If a pipe has sufficient straight section before and after the sensor, the fluid inside the pipe
will achieve laminar flow. However, the fluid becomes turbulent when there is not enough
straight section of pipe. In general, the following requirements are needed in order to
achieve laminar airflow inside a pipe.
・ The sensor inlet side requires a length of 10 times the internal orifice diameter of straight
pipe.
・ The sensor outlet side requires a length of 5 times the internal of orifice diameter of
straight pipe.
Furthermore, it is possible to reduce the influence of turbulence with regards to mounting the
sensor.
1. Against gas flow coming into the sensor
Put a guide to the sensor inlet in order to stabilize the gas flow. Flow rate is stabilized
with a long and straight guide, but you may be able to measure by attaching a guide of
about 5mm.
2. Against gas flow exiting from the sensor
By putting a buffer tank and/or by putting the orifice at the outlet of the buffer tank, it
makes squeeze the flow rate.
3. Put the jig (rotation direction in particular) so that the sensor direction can be fixed.
Airflow Airflow
Sensor Buffer tank
Guide
Orifice
Airflow Airflow
Sensor Buffer tank
Guide
Orifice
Fig.17 Example of the gas flow stabilization
6.4 The influence of environment
Flow sensors are affected by an influence of ambient environment and use conditions, which
can lead to changing output characteristics. Please be sure to check the output characteristics in
actual conditions before use, and also check the product specifications regarding characteristics
and use conditions that are guaranteed.
In this paragraph, the characteristics in the conditions of which are not defined in the product
specifications are described for customer evaluation. Please understand that it is not guaranteed
but only for reference.
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