Type 8741

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6.2. Nominal flow range of typical gases

Note:

• All values refer to 1013.25 mbar abs and 273.15 K (0 °C) (Index N)

• Other gases and gas mixtures are possible on request.

Gas

Min. Q

N

Max. Q

N

[l/min]

[l/min]

Acetylene

0.01

65

Helium

0.01

1000

Carbon dioxide

0.02

80

Air

0.01

160

Methane

0.01

160

Oxygen

0.01

160

Nitrogen

0.01

160

Hydrogen

0.01

1000

Propane

0.03

44

7.

Product operation

7.1. Measuring principle

Measurement takes place via bypass. A laminar flow element (LFE) in the main channel creates a low pressure drop. A part of the gas flow

is thereby directed into a side channel. A sensor measures the mass flow as temperature difference. The measurement is performed in a

specially shaped flow channel whose wall contains a Si chip with an etched membrane. A heating resistor and 2 temperature sensors, one

upstream and one downstream, are placed on this membrane.

If the heating resistor is fed with a constant voltage, the differential voltage of the temperature sensors indicate the gas flow over the chip.