ThermoFisher Scientific OdaLog LL, User Manual

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OdaLog ® Gas Logger User Manual
P/N: 10-1000 Revision: F, Issued: October 2019 Page: 17
7 SENSOR OPERATION
The OdaLog
®
uses an electrochemical sensor to detect levels of a specific gas in ppm (parts per million).
The sensor consists of electrolyte and electrodes packaged in a small container with a diffusion barrier which the
gas passes through.
A subsequent chemical reaction causes current flow within the sensor to change in relation to the level of gas
passing through the diffusion barrier.
This current output is then interpreted within the OdaLog ® , displayed on the LCD (in ppm) and recorded in the
OdaLog
®
’s data-logging chip.
Whilst the sensors are designed to react to their specific gas type, there are other gases that will also cause
chemical reactions within the sensor and some of these are listed in (See Section 7.1).
7.1 Sensor Cross-Sensitivity
The presence of other gases can affect the readings of the electrochemical OdaLog
®
sensors. The chart below
shows how sensors listed are likely to respond to 100 ppm of various interfering gases. There may be gases not
on this chart, which also interfere with OdaLog
® sensors.
Table 4 Sensor Cross-Sensitivity
Approximate response to Interfering Gas at 100 ppm unless noted.
H
2
S CO SO
2
NO NO
2
HCN HCL NH
3
O
3
CL
2
H
2
C
2
H
4
O C
2
H
4
CH
4
CO
2
O
d
aL
og
®
S
en
so
rs
H
2
S 100 < 2 < 20 < 6 - 20 0 0 0 N/D - 20 <1 N/D 0 0 0
CO 5 100 0 < 30 - 20 < 20 0 0 N/D 0 < 60 N/D < 100 0 0
SO
2
130 < 2 100 0 - 120 < 50 0 0 N/D - 50 0 N/D 0 0 0
NO 30 0 0 100 < 30 0 < 20 0 N/D 0 0 N/D 0 0 0
NO
2
- 10 0 - 1 0 100 0 0 0 N/D 100 0 N/D 0 0 0
HCN 350 < 1 160 - 10 - 10 100 N/D 0 N/D - 50 0 N/D
< 1
0 0
NH
3
100 0 60 20 0 N/D 0 100 N/D - 50 0 N/D 0 0 0
CL
2
- 25 0 - 1 0 100 0 0 0 N/D 100 0 N/D 0 0 0
N/D: No Data
7.2 Effects of Environmental Changes on OdaLog
®
Sensors
7.2.1 Temperature
The operating temperature range of OdaLog
®
sensors is -10°C to +40°C (14
o
F to 104
o
F) and within this range
the sensors are temperature compensated, although extreme temperature swings may cause sensor drift until the
temperature sensor stabilises.
Due to the temperature sensor being located within the OdaLog
®
body, there is a stabilisation time of up to an
hour when significant temperature changes occur.