Hanna Instruments HI 4105, Инструкция по эксплуатации

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XIV XIV XIV XIV XIV. . . . . Other Measurement T Other Measurement T Other Measurement T Other Measurement T Other Measurement Techniques echniques echniques echniques echniques
Known Addition
An unknown concentration of carbon dioxide can be deter-
mined by adding a known amount (volume and concen-
tration) of carbon dioxide standard to a known volume of
the sample. This technique is extremely useful for carbon
dioxide because changes in the sensor calibration are cor-
rected for continuously because, the standard and sample
are measured within minutes of one another. The tech-
nique can use an ideal sensor slope, but actual slopes at
the temperature of measurement should be determined
and used if possible. This will improve accuracy.
1. The volume of the unknown sample (V
Sample
) is mea-
sured accurately and placed into the closed sample
vessel. The sensor is secured in the vessel and then the
vessel is placed on a stirrer.
2. ISA is added at 1 part per 10 parts sample.
3. When the measurement is stable the mV value is
noted.
4. A known amount, volume (V
Standard
) and concentration
(C
Standard
), of CO
2
standard is then added to the sample.
mV values are again noted when the measurement is
stable.
5. The mV change is then calculated (
∆
E).
6. Using the measured and calculated values, the
sample concentration (C
Sample
) can be determined.
C
sample
=
( V
T
)10
∆
E/S
- ( V
S
’
)
C
standard
V
standard
V
sample
V
S
’
( V
sample
+ V
standard
+ V
ISA
)= V
T
( V
sample
+ V
ISA
)= V
S ’