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A simplified formula, derived from the basic formula, and based upon the assumption that the water content
of the fuel and air and the NOx content in the exhaust gases are negligible, allows the computation of
Lambda when certain components of the exhaust are measured.
B.1
Oxygen balance formula
For Lambda calculation, based upon measurements of CO, CO2, HC and O2, the following formula is
standardized: Displayed on the instrument as LAMBDA (O)
y = CO
2
+ (CO/2) + O
2
+ [H
CV
/4 x {3.5 / (3.5 + CO/CO2)} – O
CV
/2] x (CO
2
+ CO)
(1 + H
CV
/4 - O
CV
/2) x {(CO
2
+ CO) + (K
1
x HC)}
Where:
CO =
Carbon monoxide % volume measured.
CO
2
=
Carbon dioxide % volume measured.
HC =
Hydrocarbon ppm volume measured.
O
2
=
Oxygen % volume measured.
K
1
=
Conversion factor for HC is expressed in ppm vol n-hexane (C6H14) equivalent. Its value in
this formula is 6.10-4
H
cv
=
Atomic ratio hydrogen to carbon in the fuel. Nominal value is 1.7261
O
cv
=
Atomic ratio oxygen to carbon in the fuel. Nominal value is 0.0176
C - Procedures for changing Oxygen fuel cell
The Oxygen fuel cell is housed within the case of the instrument. It should be changed at an approved service
centre when readings of oxygen are erratic or when the unit will not set to 20.9% following a zero.
Note! The oxygen reading in fresh air may drift between 20.7 and 21 % this is normal.
D - Electromagnetic Compatibility (CE) Statement
This product has been tested for compliance
with the following generic standards:
EN 50081-1
EN 50082-1
and is certified to be compliant
