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1 Introduction
The Pyxis ST-772/T dissolved oxygen (DO) sensor is based on the principle of fluorescence quenching to
determine the dissolved oxygen content in water. It incorporates Pyxis’ advanced technology in the field
of fluorescence detection. The ST-772/T sensor uses dual light source detection technology with excitation
and reference light sources, offering a wide detection range and low detection limit. The sensor integrates
temperature and pressure sensors, which can perform temperature and pressure compensation for the
measurement of dissolved oxygen based on ambient environmental conditions present in the application
of use.
The ST-772/T sensor offers an easily replaceable, front loading DO membrane cap that has been indepen-
dently developed by Pyxis Lab, with a typical service life of up to two years. This unique DO membrane cap
design incorporates a black microporous PTFE membrane material designed to provide extreme scratch
resistance, extended life span and simple replacement. The flat front-end design of the ST-772/T sensor
makes this platform less prone to contamination or fouling and is easy to clean.
The sensor body is composed of 304 stainless steel and is well suited for aggressive industrial application
use. The ST-772/T sensor may be utilized in a submersed floating or submersed fixed installation format
with the Pyxis installation assembly options. It may also be used in an inline pressurized Tee assembly for-
mat (ST-772T Sensor option). All options are discussed in the
Installation section. The ST-772/T offers both
4–20mA and RS-485 Modbus outputs and is Bluetooth enabled when used in conjunction with the MA-CR
Bluetooth Adapter.
The ST-772/T sensor measures the partial pressure of the dissolved oxygen (DO) in water. In most applica-
tions, the source of DO is oxygen in the air. In other application such as in aquaculture, the source of DO is
photosynthesis. The concentration of dissolved oxygen is a derived value from the measured oxygen par-
tial pressure. The relationship between the DO concentration and the oxygen partial pressure is governed
by the law of thermodynamics. The ST-772/T sensor uses the latest USGS equation to convert the oxygen
partial pressure to DO in units of ppm or mg/L. Through setup using the
uPyxis® Mobile of Desktop App,
the ST-772/T sensor can output the measured oxygen partial pressure in other units such as percentage of
oxygen saturation.
ST-772/T User Manual service@pyxis-lab.com | +1 (866) 203-8397 2