Myron L 9PTK User Manual

Page 62

Suppose a measurement at 15°C/59°F is 900 microsiemens of true

uncompensated conductivity.

Using a 442 correction of 10 (degrees below 25) x 1.68% indicates the

solution is reading 16.8% low. For correction, dividing by (.832) yields

1082 microsiemens as a compensated reading.

A KCl correction of 10 (degrees below 25) x 1.9% indicates the solution

is reading 19% low. Dividing by (.81) yields 1111 microsiemens for a

compensated reading. The difference is 29 out of 1082 = 2.7%.

D. A Chart of Comparative Error

In the range of 1000 µS, the error using KCl on a solution that should be

compensated as NaCl or as 442, is illustrated in the graph below.

Users wanting to measure natural water based solutions to 1% would

have to alter the internal compensation to the more suitable preloaded

“442” values or stay close to 25°C. Users who have standardized to KCl-

based compensation may want to stick with it, regardless of increasing

error as you get further from 25°C. The Ultrameter III will provide the

repeatability and convertibility of data necessary for relative values for

process control.