Appendix
MXD70 Conductivity Setup and
Operating Guide
- 35 -
Appendix
Appendix B - Temperature Coefficient
Calculating the temperature coefficient of a solution
If the temperature coefficient of the solution being monitored is not known, the MXD70 series can be
used to determine that coefficient. You should set the conductivity input channel to a suitable range
and the temperature coefficient to 0.0%.
The following measurements should be made as near to the normal operating point as practical,
between 5°C and 70°C for the highest accuracy. Immerse the measuring cell in at least 500 ml of the
solution to be evaluated, allow sufficient time to stabilise, approximately one or two minutes, and then
record both the temperature and conductivity readings. Raise the solution temperature by at least
10°C and again record the temperature and conductivity readings. Using the following equation, the
temperature compensation slope can be calculated in percentage terms:
= (Gx-Gy) x 100%
Gy(Tx-25) - Gx(Ty-25) (base temperature 25°C)
Note: If base temperature is set to 20°C, then replace 25 with 20 in the above equation.
Term Description
Gx
Conductivity in μS/cm at temperature Tx
Gy
Conductivity in μS/cm at temperature Ty
Note: One of these measurements can be made at ambient temperature.
Set the temperature compensation slope to the calculated value. The temperature compensation is
now set up for normal operation.
If it is difficult or impossible to evaluate the temperature compensation slope using this method, a 2.0
% / °C setting will generally give a good first approximation until the true value can be determined by
independent means.
Temperature Data
The table below lists approximate resistance values of temperature sensors that may be used with the
MXD70 Series. Not all options are available on all models.
Temperature
( C )
PT1000
RTD
PT100
RTD
1K
Thermistor
3K
Balco
0
1000.0 100.00 2691 2670
10
1039.0 103.90 1779 2800
20
1077.9 107.79 1204 2930
25
1097.3 109.73 1000 3010
30
1116.7 111.67 833.7 3070
40
1155.4 115.54 589.0 3160
50
1194.0 119.40 423.9 3320
60
1232.4 123.24 310.5 3470
70
1270.7 127.07 231.0 3570
80
1308.9 130.89 174.5 3740
90
1347.0 134.70 133.6 3830
100
1385.0 138.50 103.6 4020
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