Myron-l PS6FCE User Manual download pdf (Page 45)

water to be pretreated by RO. Assume it is 45°C and reads 1500 µS

uncompensated.

1. If NaCl compensation is used, an instrument would report 1035

µS compensated, which corresponds to 510 ppm NaCl.

2. If 442 compensation is used, an instrument would report 1024

µS compensated, which corresponds to 713 ppm 442.

The difference in values is 40%.

In spite of such large error, some users will continue to take data in

the NaCl mode because their previous data gathering and process

monitoring was done with an older NaCl referenced device.

Those who want true TDS readings that will correspond to evaporated

weight will select the correct Solution Type.

XXI. TEMPERATURE COMPENSATION (Tempco)

and TDS DERIVATION

The Po o l Pr o contains internal algorithms for characteristics of the 3

most commonly referenced compounds. In the display, the solution type

being used is shown to the left.

When taking conductivity measurements, the Solution Selection

determines the characteristic assumed as the instrument reports what a

measured conductivity would be if it were at 25°C. The characteristic is

represented by the tempco, expressed in %/°C. If a solution of 100 µS at

25°C increases to 122 µS at 35°C, then a 22% increase has happened

over this change of 10ºC. The solution is said to have a tempco of 2.2

%/ºC.

Tempco always varies among solutions because it is dependent on their

individual ionization activity, temperature and concentration. This is why

the Po o l Pr o features mathematically generated models for known salt

characteristics that also vary with concentration and temperature.

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Myron-l PS6FCE User Manual Page 45