Endress+Hauser Liquisys M CLM253 - Page 40

Commissioning Liquisys M CLM223/253
40 Endress+Hauser
Ultrapure water compensation (for conductive sensors)
For pure and ultrapure water, algorithms are saved in the transmitter that consider the
self-dissociation of ultra pure water and its strong temperature dependency. They are used
for conductivity levels of approx. 100 μS/cm.
Two types of compensation are available:
• NaCl ultrapure water compensation: this is optimized for pH-neutral contamination.
• HCl ultrapure water compensation: this is optimized for measuring the acid conductivity
downstream of a cation exchanger. It is also suitable for ammonia (NH3) and caustic
soda (NaOH).
• The ultrapure water compensation types always refer to a reference temperature of
25 °C (77 °F).
• The lowest conductivity displayed is the theoretical limit value of ultrapure water at
25 °C (77 °F) of 0.055 μS/cm.
Temperature compensation with table
For devices with the Plus Package, it is possible to enter a table with temperature
coefficients α as a function of the temperature. The following conductivity data of the
medium under measurement are required to use the alpha table function for temperature
compensation:
Value pairs comprising the temperature T and conductivity κ with:
• κ(T0) for the reference temperature T
0
• κ(T) for the temperatures that occur in the process
T
1
T
0
T
2
T T
k
2
k
1
k
k( )
T
0
T
1
T
2
a
1
a
2
a
A
B
A0008944
 24 Determination of the temperature coefficient
A Required data
B Calculated α values
Use the following formula to calculate the α values for the temperatures that are relevant
in your process:
a =
100%
k(T )
0
k k(T) - (T )
0
T - T
0
.
; T T¹
0
A0009162
Enter the α-T value pairs obtained in this way in the T4 and T5 fields of the ALPHA TABLE
function group.
Use this function group to change the settings for temperature measurement.