XS Instruments 60 VioLab Series, Инструкция по эксплуатации

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29
Rev. 1.0 31/01/2020
EN
If the temperature of a sample increases, its viscosity decreases and this leads to an increase in the mobility
of the ions and the measured conductivity, although the concentration remains constant.
For each conductivity measurement, the temperature to which it refers must be specified, otherwise a result
without value is obtained. Generally, temperature refers to 25 °C or, more rarely, 20 °C.
This device measures Conductivity at real temperature (ATC or MTC) and then converts it to the reference
temperature using the correction factor chosen in program P3.4.
• Access this setup menu to set the temperature to which you want to refer the Conductivity
measurement.
•
The device can report conductivity from 15°C to 30°C . By default, it is 25°C which is correct for most of
the analyses.
P3.4 Temperature compensation Factor
It is important to know the temperature dependence (% change in Conductivity per °C) of the sample being
measured.
• Access this menu to change the temperature compensation factor.
By default, 1.91% / °C is set which is suitable for most of the analyses.
Press the key , the value flashes and as indicated by the icon , use the directional keys
to enter the new coefficient. Confirm with key .
Compensation coefficients for special solutions and for groups of substances are shown in the following
table:
Compensation coefficients for calibration standards at different temperatures for T
ref
25 ° C are
shown in the following table:
°C 0.001 mol/L KCl (147µS) 0.01 mol/L KCl (1413 µS) 0.1 mol/L KCl (12.88 mS)
0 1.81 1.81 1.78
15 1.92 1.91 1.88
35 2.04 2.02 2.03
45 2.08 2.06 2.02
100 2.27 2.22 2.14
To determine the calibration coefficient of a solution, the following formula is applied:
𝑡𝑡𝑡𝑡 = 100 𝑥𝑥
𝐶𝐶
𝑇𝑇2
− 𝐶𝐶
𝑇𝑇1
𝐶𝐶
𝑇𝑇1
(
𝑇𝑇
2
− 25) − 𝐶𝐶
𝑇𝑇2
( 𝑇𝑇
1
− 25)
Where tc is the temperature coefficient to be calculated , C
T1
and C
T2
are Conductivity at
temperature
1 (T1)
and at temperature 2 (T2).
Each result with "correct" temperature is plagued by an error caused by the temperature coefficient. The
Solution (%/°C) Solution (%/°C)
NaCl Saline solution 2.12 1.5% Hydrofluoric acid 7.20
5% NaOH Solution 1.72 Acids 0.9 - 1.60
Diluted ammonia solution 1.88 Bases 1.7 – 2.2
10% Hydrochloric acid solution 1.32 Salts 2.2 - 3.0
5% Sulfuric acid solution 0.96 Drinking water 2.0