E Instruments E4500, Operating & Maintenance Manual

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14.6 CxHy sensor for measurement of the Unburned hydrocarbons
The Unburned 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.
Calculation example:
Type of gas:
iso-butane
Relative response: 0.6
Gain adjustment: 1.67
Reading value (related to metane): 1.34
Value = reading value x gain adjustment
Example:
1.34 x 1.67 = 2.24
14.7 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.
GAS / VAPOR
RELATIVE RESPONSE
(with respect to Methane)
GAIN ADJUSTMENT
Ethanol 0.75 1.33
Iso-Butane 0.60 1.67
Methane 1.00 1.00
Methanol 1.00 1.00
n-Butane 0.60 1.67
n-Heptane 0.45 2.22
n-Hexane 0.50 2.00
Propane 0.70 1.43
Configuration→Analysis→Autozero (SEE SECTION 9.2.6) →
OK
Purging
s
0
Autozero
s
60
Configuration
Autozero
07/08/14
10:00
O
Purging
s
0
Autozero
s
06 0
Configuration
Autozero
07/08/14
10:00
OK
O
Purging
s
0
Autozero
s
18 0
Configuration
Autozero
07/08/14
10:00
OK
O
Purging
s
0
Autozero
s
180
Configuration
Autozero
07/08/14
10:00
O