Sper Scientific 850038 Pure Water Meter - Manual (Page 44)

Appendix D: Temperature Effect
Conductivity measurements are temperature
dependent, if the temperature increases, conductivity
increases. eg: the conductivity measured in a 0.01
0 M KCl solution at 20 C is 1.273 mS/cm, whereas, at
0 25 C, it is 1.409 mS/cm.
The concept of reference temperature (Normalization
temperature) was introduced to allow the comparison
of conductivity results obtained at different temperature.
0 0 The reference temperature is usually 20 C or 25 C.
The conductivity meter measures the actual COND.
and temperature and then converts it to the reference
temperature using a temperature correction function
and displays the conductivity at the reference temp..
It is mandatory to always associate the temperature
together with a conductivity result. If no temperature
correction is applied, the conductivity is the value
taken at measurement temperature. The 830x meter
used linear temperature correction.
Linear temperature correction:
In moderately and highly conductive solutions,
temperature correction can be based on a linear
equation involving a temperature coefficient ( ). The
coefficient is usually expressed as a conductivity
0 variation in %/ C.
Linear temperature correction is used, e.g. for saline,
acids and leaching solutions.
where:
K
= Conductivity at Tref
Tref
K = Conductivity at T
T
T = Reference temperature
ref
T = Sample temperature
= Temperature coefficient
Note: the correction is accurate only within a limited
temperature range around T1 and T2. The greater the
difference between T and Tref, the higher the risk of
error.
Calculating Temperature Coefficients ( )
By measuring the conductivity of a sample at
temperature T1 close to Tref and another tempe-
rature T2, you can calculate the temperature
coefficient by using the following equation:
K
Tref
=
T-T
ref
K
T
100
100+ ( )
K
T2-
K
T1
) 100 (
=
T
2-
T
1
) ( K
T1
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