Carl Roth COND 50 VioLab, Instruction Manual

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23
UM Serie 50VioLab EN rev.1 19.05.2020
EN
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:
𝑡𝑐 = 100𝑥
𝐶
𝑇2
− 𝐶
𝑇1
𝐶
𝑇1
(𝑇
2
− 25) − 𝐶
𝑇2
(𝑇
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
better the temperature correction, the lower the error. The only way to eliminate this error is not to use the
correction factor, acting directly on the sample temperature.
Select 0.00% / °C as the temperature coefficient to deactivate the compensation. The displayed Conductivity
value refers to the temperature value measured by the probe and not related to a reference temperature.
P3.6 COND calibration Data
Access this menu to get information on the last calibration performed. The following screens will
automatically scroll on the display:

First screen: beakers indicating the buffers used for calibration.

Second and possibly third, fourth and fifth screens: Value of the actual cell constant in
the measurement range indicated by the beaker.
Note: The instrument accepts calibrations with a maximum tolerance of 40% on the nominal
value of the cell constant only.
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