Mass flow sensors measure gas flow in many applications. They are usually mounted inside a system that very often prevents easy direct reading of the flow if the display is integral with the mass flow sensor. A typical output is 0V for 0 flow and 5V for the maximum range of the flow sensor.

A simple SPAN (gain) adjustment on a DPV-3 can set 5V to display 2000 counts on the display. However, the flow displayed is only valid for a standard gas, usually nitrogen. Other gases require a conversion factor to be applied to a reading. For example:

The actual flow rate of a particular gas = flow rate of nitrogen X correction factor.

If the correction factor is less than one, such as 0.73 for ammonia (NH3), the DPV-3 can be simply readjusted for 2000 X 0.73 = 1460 with a 5V input.

If the correction factor is greater than one, such as 1.45 for helium (He), another input voltage must be selected such that the reading is less than 2000 (above that is an over range condition for the DPV-3).
2000 X 1.45 = 2900, therefore divide by 2, and a 2.5 V input should be adjusted to display 2900/2 = 1450.

Note: the correction factors for different gases vary for each mass flow transducer and should be requested from the manufacturer.

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