Yokogawa EXA ISC202 2-wire Conductivity Transmitter/Analyzer - Manual (Page 52)

IM 12D06A03-01E
5-10 Parameter setting
Calculation example
Calculate the temperature co-efficient of a liquid from the following data.
Conductivity 124.5 μS/cm at a liquid temperature of 18.0 °C and a conductivity 147.6 μS/cm at a liquid
temperature of 31.0 °C.
Substituting the data in the above formula gives the following result.
Set the temperature coefficient in the EXA transmitter.
2-C. Checking
When the temperature coefficient already set is accurate, the conductivity to be displayed must be con-
stant regardless of liquid temperature. The following check will make sure that the temperature coeffi-
cient already set is accurate.
If, when the liquid temperature is lowered, a larger conductivity value is indicated, the temperature coef-
ficient already set is too small.
The opposite also applies. If a smaller conductivity value is indicated, the temperature coefficient already
set is too large. In either case, change the temperature coefficient so that the conductivity no longer
changes.
3. Matrix compensation
The compensation matrix is a table of temperature and conductivity values at differing concentrations.
These values are used to calculate the temperature compensation applicable for a particular solution.
Choose the component that you will be measuring in your application, and where appropriate the con-
centration range. EXA will do the rest.
4. Manual temperature compensation (Section 5-2-4 and 5-2-5)
If the standard compensation function is found to be inaccurate for the sample to be measured, the
transmitter can be set manually for a linear factor on site to match the application.
The procedure is as follows:
1. Take a representative sample of the process liquid to be measured.
2. Heat or cool this sample to the reference temperature of the transmitter (usually 25 °C).
3. Measure the conductivity of the sample with the EXA and note the value.
4. Bring the sample to the typical process temperature (to be measured with the EXA).
5. Adjust the display indication to the noted value at the reference temperature.
6. Check that the temperature compensation factor has been changed.
7. Insert the conductivity cell into the process again.
5. Other possibilities (section 5-3)
1. Enter calculated coefficient.
2. Enter matrix temperature compensation.
147.6 - 124.5
x 100% = 1.298%/ ºC α =
124.5(31.0 - 25) - 147.6(18.0 - 25)