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5.6 CxHy sensor for measurement of the unburnt hydrocarbons
The unburnt hydrocarbons are chemicals produced by an incomplete combustion of molecules (hydrocarbons)
made of Carbon and Hydrogen.
These are usually named as HC or (better) CxHy: when this is filled with the actual values for the number of C
and H atoms, the actual type of fuel is exactly defined. In case of Methane, as an example, the correct formula is
CH4. In the following table is shown the cross sensitivity of the CxHy sensor when exposed to fuels different from
Methane (CH4), assumed as 1.00.
GAS / VAPOR
Ethanol
Iso-Butane
Methane
Methanol
n-Butane
n-Heptane
n-Hexane
Propane
Calculation example:
Type of gas:
Relative response:
Gain adjustment:
Reading value (related to metane):
Value = reading value x gain adjustment
Example:
1.34 x 1.67 = 2.24
5.7 Installing the CxHy sensor
When the CxHy (position S3/S4) is mounted in the instrument, it is mandatory to configure the autozero by set-
ting it at 180 seconds, in order to allow for a proper pre-heating of the sensor itself.
The instrument battery life, once the CxHy is installed, lasts 10 hours, provided no printing is made.
CONFIGURATION
►Fuel
Measurement units
O
Reference
2
Display contrast
Autozero/Pump
▼
CONFIGURATION
AUTOZERO/PUMP
Fuel
►Autozero
Measurement units
Pump
O
Reference
2
Display contrast
►Autozero/Pump
▼
K900000000SE 022628A0 071013
RELATIVE RESPONSE
(with respect to Methane)
0.75
0.60
1.00
1.00
0.60
0.45
0.50
0.70
iso-butane
0.6
1.67
1.34
AUTOZERO/PUMP
15
s
Autozero
15
s
on
Pump
on
GAIN ADJUSTMENT
1.33
1.67
1.00
1.00
1.67
2.22
2.00
1.43
AUTOZERO/PUMP
Autozero
25
s
Pump
on
1
2
3
4
5
6
7
8
63
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