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Data logging
CO
probe
2
Ref :
453 076
ENGLISH
2
How it works
2.1 Description
Probe body
2.2
Electro-chemical principle of the functioning
mechanism
The following reaction takes place in the electrolyte of the CO
CO
2
The following is the dissociation constant for the reaction:
K
-
Because the HCO
concentration is high in the electrolyte, it varies little,
3
+
and one thus obtains [H
] = K' [CO
to the partial pressure of CO
measuring the pH of the electrolyte.
The CO
probe is not compensated for temperature (in contrast to the
2
oxygen probe). It would therefore be necessary, in theory, to calibrate the
probe for each temperature change. In practice, however, using the CO
probe at a nearly constant ambient temperature is sufficient.
The CO
probe has a response time of ca. 2 min. (10 sec. for the O
2
Consequently, when you remove the probe from the calibration solution after
having adjusted the "slope," it is necessary to wait ca. 5 to 10 minutes for it
to display a level lower than 0.2%.
13
+
+ H
O
H
+HCO
2
+
-
[H
] [HCO
3
=
[CO
]
2
] = K'' pCO
(wherein pCO
2
2
). The CO
concentration is thus measured by
2
2
Glass electrode
Probe head
Membrane
probe:
2
3-
]
corresponds
2
2
probe).
2
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