QuadraTherm680i/780iGas & Mixture Database

Improved Gas Accuracy.  One Unit at a Time.

For use with ALL QuadraTherm mass flow meters, Sierra's proprietary Gas Database offers end users gas mix files that have a higher accuracy (between +/- 0.5% to +/- 3.0% of full scale for the 780i and +/- 0.75% to +/- 3.0% of full scale for the 640i). This is generally the result of actual gas calibrations at Sierra.  

Thermal mass flow meters depend on knowing the thermodynamic and transport properties of the gas being measured as a fundamental part of the principal of operation.

Gas Packets

The gases in Sierra's Gas Database are more accurate because they store proprietary "gas packets". A "gas packet" is analogous to the DNA of a specific gas. It stores all the parameters needed to instantly calculate the thermodynamic and transport properties of every gas or gas mixture versus temperature and pressure.  

As Sierra improves and optimizes the gas packets over time, largely via empirical data collected on each instrument calibrated, the capability improve the accuracy of the QuadraTherm mass flow meter exists.

How Does it Work?

Using the Smart Interface Program(SIP) software, included free with every instrument, the customer can download available gases to the meter and manage them on-board the instruments with Dial-A-Gas®. As new improved gases are added to the database, the customer will be notified as they will became available to the instrument via the SIP.

 Video:  Watch video on how to download gases to your meter.

Make Your Own Gas Mixtures

Instrument software also features a unique multi-gas flow totalizer and qMix™ gas mixing tool to create custom gases or gas mixes to compensate for compositional changes in the field without the need to return the instrument to the factory for recalibration. 

Video:  Watch video on how to use the qMix gas mixing feature.


Gas Database Contents

Currently, the database has mapped the gases and mixtures listed below, and it continues to grow and improve by the day. Furthermore, the millions of data points collected over time in Sierra’s metrology laboratories are used to tune the instrument for better performance and accuracy. Expect 100’s of gas and gas mixture combinations in the future.


Pure Gases

  1. Air
  2. Methane
  3. Nitrogen
  4. Oxygen
  5. Hydrogen
  6. Carbon Dioxide
  7. Helium
  8. Argon
  9. Propane
  10. Chlorine


Common Gas Mixes:

Natural Gas (US Mean)
Mass Fractions:

  • 93% Methane
  • 03% Ethane
  • 01% Propane
  • 02% Nitrogen
  • 01% CO2

Natural Gas (PG and E California)
Mass Fractions:

  • 95% Methane
  • 03% Ethane
  • 01% Nitrogen
  • 01% CO2

SASOL Gas (Methane Rich)
Mass Fractions:

  • 99% Methane
  • 01% Hydrogen

Coal Gas I (Town Gas)
Mass Fractions:

  • 50% Hydrogen
  • 35% Methane
  • 10% CO
  • 05% Ethylene

Coal Gas II (Town Gas)
Mass Fractions:

  • 49% Hydrogen
  • 36% Methane
  • 15% CO

Digester Gas
Mass Fractions:

  • 60% Methane
  • 40% CO2

Blast Furnace Gas
Mass Fractions:

  • 50% Nitrogen
  • 23% CO2
  • 22% CO
  • 05% Hydrogen

Flare Gas
Mass Fractions:
  • 55% Methane
  • 45% Propylene