Myron L 9PTK - Manual (Page 64)

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Company calls “natural water”. These are modeled in a mixture called
“442™” which the Myron L Company markets for use as a calibration
standard, as it does standard KCl and NaCl solutions.
The Ultrameter III contains algorithms for these 3 most commonly
referenced compounds. The solution type in use is displayed on the
left. Besides KCl, NaCl, and 442, there is the “User” choice. The
benefit of “User” is that one may enter the temperature compensation
and TDS ratio by hand, greatly increasing accuracy of readings for a
specific solution. That value remains a constant for all measurements
and should be reset for different dilutions or temperatures.
C. When does it make a lot of difference?
First, the accuracy of temperature compensation to 25°C determines the
accuracy of any TDS conversion. Assume we have industrial process
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.
Selecting the correct Solution Type on the Ultrameter III will allow the
user to attain true TDS readings that correspond to evaporated weight.
If none of the 3 standard solutions apply, the User mode must be used.
Temperature Compensation (Tempco) and TDS Derivation below, details
the User mode.
XXii. temPeratUre cOmPensatiOn (tempco) and tDs
DerivatiOn
The Ultrameter III contains internal algorithms for characteristics of the
3 most commonly referenced compounds. The solution type in use is
displayed on the left. Besides KCl, NaCl, and 442, there is the User
choice. The benefit of User mode is that one may enter the tempco and
TDS conversion values of a unique solution via the keypad.