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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 “E”
Automatic Calculation of Theoretical 100% Dissolved Oxygen Saturation
at any Temperature & Pressure for Accurate Calibration & Measurement
The HiQDT-DO sensor has preprogrammed the correct 100% dissolved oxygen saturation levels valid at any
temperature and pressure. This is important for two main purposes: 1) to ensure accurate calibration of the
sensor which is performed dry in air and 2) when the percent (%) saturation is displayed and output for
purposes of monitoring and control. The graph below demonstrate the impact of both temperature and
pressure on the dissolved oxygen (DO) ppm levels that constitute 100% saturation condition.
For the calibration function, either the field condition should be 100% relative humidity for best accuracy or
else the sensor should be suspended dry in air but over a water source to simulate locally the 100% relative
humidity condition. The water molecule in air (humidity) is then saturated with oxygen in manner that can be
fully described by the ambient temperature and pressure as shown above. When placed into service, the
galvanic DO sensor will measure the ppm levels at the installation depth. To convert this measured ppm
value into percent (%) saturation the HiQDT-DO sensor uses the internally stored curve visualization above.