A new instrument to measure the Wobbe index of natural gas has been de
veloped and tested. The instrument detects the residual oxygen content
of the flue gases after a known amount of gas is burned with a known
amount of air. This residual oxygen content is a measure for the Wobbe
index. The instrument has a fast response and a low noise level which
makes it suitable for use in burner control systems. The measurement
is hardly affected by external influences so an expensive conditioned
room will not be required.