PRECISION GAS FLOW METERS & GAS FLOW CONTROLLERS

Frequently Asked Questions

Frequently Asked Questions (FAQs)

What reference conditions (pressure and temperature) does Vögtlin use?

Unlike liquids, gases can be compressed. The volume changes when the temperature and/or the pressure change. When specifying a gas volume, the reference temperature and the reference pressure must thus also always be specified. The flow unit is than referred to as normalized (f.i. ln/min) or standardized flow (f.i. ls/min)

When we refer to “Normal” flow we in general use:
Temperature Tn = 273,15 K, corresponds to 0 °C
Pressure Pn = 1013,25 mbar abs

When we refer to “Standard” flow we in general use:
Temperature Tn = 293,15 K, corresponds to 20 °C
Pressure Pn = 1013,25 mbar abs
See also: http://en.wikipedia.org/wiki/standard conditions

Please note: Not everyone understands standard conditions in the same way. In the case of reference pressure, everyone agrees, but in the case of reference temperature, there are differences:

  • Gas suppliers in Europe do not use 0 °C, but 15 °C as their “Normal condition”

To avoid misunderstandings, the reference conditions are specified clearly in our correspondence.
On request, we also deliver the devices with another reference temperature.