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Introduction
The ST-565 Series inline fluorometers are patented to Pyxis Lab Inc. These devices utilized UV light fluores-
cence to detect Halogenated Tolytriazole (HST with ST-565) and Tolytriazole (TTA with ST-565T) content in
water. The results are instantaneous and, with proper application understanding, results are highly reliable.
It is important to note that this technology is not wet chemistry testing for azole content and variations may
be observed depending on the quality of the water sample. In certain waters the background of other or-
ganic matter may cause a false positive reading of azole due to UV fluorescence or absorbance. Inconsistent
makeup water quality with little organic loading (ie. city water makeup) and systems with no known organic
contamination (ie. hydrocarbon) this technology is very accurate in comparison to wet chemistry methods.
The ST-565 Series probe does not differentiate between azole species or reacted versus unreacted azole.
The device measures the total UV fluorescence signature of the azole and offers the final value as ppm
Halogenated Tolytriazole (HST with ST-565) and Tolytriazole (TTA with ST-565T). It is incumbent for the user
to identify the correlation to exact wet chemistry values and potential background interference should be
accounted for by identifying untreated makeup for UV fluorescent signal and removing that from the final
value measured.
The ST-565 Series probe will not work in waters containing Nitrite treatment as Nitrite absorbs UV light
and will result in a false high value. With these application limitations clearly understood, the ST-565 Se-
ries probe is commonly used for rapid azole validation, dramatically reducing service time enabling water
treaters to adjust their programs accordingly. It is important to note however, that there are some applica-
tions (surface makeup water systems or high organic loading/contaminated systems) where this technology
is not ideal due to a high degree of interference. The user needs to understand the dynamics of their system
and evaluate its use accordingly.
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Main Features
The ST-565 Series measures Halogenated Tolytriazole (HST with ST-565)/Tolytriazole (TTA with ST-565T) in
a water sample and includes the following features:
• Easy calibration with using
uPyxis®
Mobile or Desktop App.
• Automatic compensation for turbidity and color.
• Water sample does not need to be acidified. Sample pH between 6.4 to 10.0 and the sample PTSA
concentration (<300 ppb) do not affect the azole measurement.
• Diagnostic information (probe fouling, color or turbidity over range, failure modes) are available in
uPyxis®
App or via Modbus RTU.
• Easy to remove from the system for cleaning and calibration without the need for any tools.
ST-565 Series User Manual
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