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A
dvanced
S
ensor
T
echnologies,
I
nc. U.S.A.
Website:
www.astisensor.com
IOTRON
TM
Trademark of ASTI
IOTRON
TM
pH / ORP / ISE / DO / Conductivity Measurement Products Lines
APPENDIX “F”
Automatic Calculation of Theoretical 100% Dissolved Oxygen Saturation
at any Temperature & Pressure for Accurate Calibration & Measurement
The HiQDT-DO has preprogrammed the correct 100% dissolved oxygen saturation levels valid at not only any
temperature and pressure but also corrected for salinity. This is important for applications where not only
fresh water will be present but also for brackish and salt water sources in variable amounts. The graph below
demonstrates the impact of salinity on the dissolved oxygen (DO) ppm levels that constitute 100% saturation
condition at the nominal 760mm pressure condition. For simplicity of visualization just one set of curves is
shown although the analyzer can perform this compensation any temperature, pressure or salinity.
This salinity correction is only required as a correction to the computation of the % saturation from the
measured DO ppm levels for the inline measurement. Since the calibration is done dry in air, salinity
correction is not required for this part of operation. Since the impact of salinity is considerable as shown in the
graph above, it must be corrected carefully at any level of salinity and temperature. The salinity value in
standard PSU (PPT) units can be entered into the HiQDT-DO sensor to perform this correction. The value of
the salinity can be determined by a handheld meter or else monitoring continuously using a conductivity
transmitter from which one can readily convert into common salinity units.