8.4.Routine servicing and care
Minor dust and dirt can be removed using a soft brush. Cleaning on a more intensive
scale, as required if the electrodes are very dirty, may result in the distances between
electrodes being slightly altered; this may have an adverse effect on results.
Checking
In the following circumstances it makes good sense to check the probe :
●
in the event of the geometry changing (e.g. electrode spacing)
●
after use in extreme conditions (e.g. high temperatures)
●
if the probe produces measured results that are not plausible
Adjusting the D7 conductivity probe
A conductivity probe of this type is adjusted at two measuring points :
1.
in a dry condition
at 0 mS/cm
sensor adjustment
by pressing key 'ZERO'
2.
in reference solutions
as per measuring range
e.g. 147 μS/cm - 0.001 mol KCl reference solution at (25 ±0,1) °C
in measuring range 500 μS or
12.88 mS/cm - 0.1 mol KCl reference solution at (25 ±0,1) °C
in measuring range 50 mS
Enter setpoint
(reference value) in function 'Setpoint'
Sensor adjustment
by pressing key 'ADJ'.
Throughout the adjustment procedure the solution must be kept at a constant
temperature (25 ±0.1)°C
The probe can also be adjusted outside of standard conditions (25 ±0.1) °C.
Zero-point adjustment is performed as described above. For the purposes of gain ad-
justment the value of the reference solution at a known temperature (see Table 1) is
compared with the deviating value determined on site; this ratio is manually entered as
correction value in the ALMEMO
®
plug under 'Gain correction' (GC).
Example
Adjustment of probe using 1 mol KCl reference solution at measured solution tempera-
ture 20.0 °C.
Value for reference solution at solution temperature 20.0 °C 102.09 mS/cm (Table 1)
Measured value at solution temperature 20.0°C : 98.72 mS/cm
Table 1:
Electrical conductivity κ in mS/cm of KCL standard solutions
as a function of temperature t and concentration:
- 17 -
GC
=
Value for reference solution at solution temperature 20°C
Measured value at solution temperature 20°C
=
102,09
98,72
=
1,034
