FHAL200DU Datasheet, PDF (2/4 Pages) Sensortechnics GmbH – Mass flow sensors for gases

FHA Series
Mass flow sensors for gases
FLOW SENSOR CHARACTERISTICS³
(V_S = 10 ±0.01 V, T_A = 25°C)
Part no.
Flow range (full scale)
FHAL200DU
200 SLPM¹
Output voltage @ trim point
5.0 ±0.36 V @ 200 SLPM¹
PERFORMANCE CHARACTERISTICS
(V_S = 10 ±0.01 V, T_A = 25°C)
Characteristics
Min.
Typ.
Max.
Unit
Zero offset
0.95
1.0
1.05
V
Repeatability and hysteresis (combined)
Ratiometricity error²
Temperature effects
Offset⁴
-20 to 85 °C
±0.30
±0.25
±0.5
% reading
V
Span
25 to 10 °C
-2.0
25 to 40 °C
2.0
% reading
Response time
6.0
ms
Common mode pressure
25
psi
Notes:
1 _{SLPM denotes standard liters per minute, which is a flow measurement referenced to standard conditions of 0°C, 1 bar, 50% RH.}
2 _{Output voltage is ratiometric to supply voltage}
3 _{A 5 micron filter is recommended for all devices.}
4 _{Shift is relative to 25 °C.}
NOTICE: LAMINAR FLOW
Due to the fast response time of the sensor, these specifications were generated using laminar flow.
Airflow instability or “turbulence” present in the airstream will result in an increase in measurement
uncertainty.
The turbulent flow problem can be corrected by either straightening the airflow using flow laminarizing or
by slowing the response of the sensor using a simple RC time constant on the output of the sensor.
This, of course, slows down the sensor response time. The values needed depend on the amount of
turbulence present in the application.
Several techniques for laminarizing the flow include adding hex shaped honeycombs, foam, screen
materials or adding constrictors (frits) to the flow stream. There are various commercial laminar flow
elements that can be purchased. Unfortunately the greater the efficiency of the laminarizer, the greater
the increase in pressure drop in order to establish a given flow rate. Plastic honeycomb material
probably gives the most improvement for the least pressure drop. In any test fixture, the avoidance of
sharp radii is an absolute requirement.
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