ASF1400 SENSIRION, ASF1400 Datasheet - Page 4

• Manufacturer Part Number: ASF1400
• Description: SENSOR, MASS FLOW
• Manufacturer: SENSIRION

Specifications of ASF1400

• Pressure Max: 120Pa
• Supply Voltage Range Dc: 7V To 18V
• Accuracy: ± 1%
• Air Mass Flow Range: -400sccm To 400sccm
• Svhc: No SVHC (15-Dec-2010)
• Connection Size: 5mm
• Measuring Range: .015 To 400 Sscm
• Supply Voltage Dc: RoHS Compliant
• Response Time: 142ms
• Rohs Compliant: Yes

ASF1400 Bidirectional Mass Flow Meter
1.1 Gas Flow Characteristics
Figure 2 shows the applied gas flow vs. the digital
output of the ASF1400.
Figure 2: ASF1400 transfer characteristics.
1.2 Sensor Principle and Gas Types
The ASF1400 device detects mass gas flow by
measuring heat transfer. A heating resistor on a
thermally insulated membrane is kept above ambient
temperature. In the presence of gas flow, the
temperature distribution up- and downstream is
disturbed. This asymmetry is then measured. Due to
the minimal thermal mass of the membrane,
symmetrical arrangement, and accurate temperature
measurement, the revolutionary specifications of the
ASF1400 devices are achieved.
The above mentioned thermal principle requires
information about the gas type to be measured. The
ASF1400 is available for air and nitrogen. Other gas
types are available on request.
In Figure 3 the repeatability of the ASF1400 devices
is compared with the repeatability of a typical Mass
Flow Controller (MFC). It emphasizes the superior
performance of the ASF1400 device.
Figure 3: Comparison of the repeatability of the
CMOSens
Mass Flow Controller (MFC).
www.sensirion.com
0.5
0.4
0.3
0.2
0.1
0
0
-250
-500
500
250
®
0
-500
ASF1400 device compared to a typical
100
-250
Massflow [sccm]
Mass Flow [sccm]
200
200
Specs of typical MFC
Repeatability ASF 1400
0
300
250
500
400
Version 2.1
1.3 Gas Flow and Pressure Difference
The
measurements. However, there is a well defined
relation between mass flow and pressure drop. This
relation is shown in Figure 4. On request the
ASF1400 can also be calibrated for the pressure drop
at its output (for more details refer to the
documentation of the Sensirion Differential Pressure
Sensor ASP1400).
Figure 4: Differential Pressure vs. Mass Flow of
ASF1400 Device.
1.4 Adjusting the Measurement Range
To adjust the measurement range, the ASF1400
device is used in conjunction with a bypass
configuration (see Figure 5). Only a sample of the
total flow actually gets directed through the bypass
channel and the sensor system. A tube with flow
restrictor and all required connection items are
included in the Mass Flow Meter Evaluation Kit EK-
F1, also available from SENSIRION AG.
Figure 5: Extending the measurement range of the
ASF1400 device using a bypass configuration. Only a
sample of the total flow actually gets directed through
the bypass channel and the sensor. Shown tube with
flow restrictor is included in the EK-F1 evaluation kit.
- 100
- 150
- 50
150
100
50
0
ASF1400 is
- 400
Flow restrictor
- 200
calibrated for mass flow
Massflow [sccm]
0
200
4/11
400