Chemtrol Product - In-Line PTSA Fluorometer Probe
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In-Line PTSA Fluorometer Probe

Pyxis ST-500 In-Line Fluorometer Probe

The Pyxis ST-500 inline fluorometer probe measures the concentration of fluorescence tracer PTSA (pyrenetetrasulfonic acid) in water. It can be simply inserted to the compression fitting port of a custom-made tee. The companion tee has two 3/4″ female NPT ports and can be placed to an existing 3/4″ sample water line. The 4-20mA current output of the ST-500 probe can be connected to any controller that accepts an isolated or non-isolated 4-20mA input.

The ST-500 probe is a smart device. In addition to measuring fluorescence, the ST-500 probe has extra photo-electric components that monitor the color and turbidity of the sample water. This extra feature allows automatic color and turbidity compensation to eliminate interferences common in real-world samples.


  • Eliminates Color & Turbidity Interference!
  • ST500 = PTSA (0-300ppb)
  • 4-20mA & Modbus RS485 Connection
  • Wireless Calibration, Smart Phone or Pyxis SP Units
  • Probe fouling diagnostics through PC


Features of the Pyxis ST-500

The ST-500 includes the following features:

  • Easy calibration with using uPyxis mobile or desktop app.
  • Automatic compensation for turbidity up to 150 NTU and color created by up to 10 ppm iron or equivalent to 10 ppm humic acid.
  • Diagnostic information (probe fouling, color or turbidity over range, failure modes) are available in uPyxis app or via CHEMTROL web server.
  • The ST-500 probe can be easily removed from the system without the need of any tools for being cleaned.

Product Features

Pyxis ST-500 Specifications

The Pyxis ST-500 probe uses a narrow wavelength band gallium phosphide photodiode and high temperature-tolerant and humidity-resistant optical filters. This combination greatly enhances the robustness of the probe. It can be operated under a wide range of ambient conditions without the need of humidity and temperature regulation. The performance of the ST-500 probe can be stable and consistent for a long period time.

  • PTSA Range 0 to 300 ppb, precision 0.2 ppb (3 sigma)
  • Power Supply 24 (±2) VDC, 65 mA
  • Signal Output 4-20 mA and RS-485 Modbus RTU
  • Storage Temperature -7 °C – 60 °C
  • Operational Temperature 4 °C – 40 °C
  • Sample Pressure 100 PSI
  • Protection Grade IP67, Fully Dustproof & Waterproof
  • Regulation CE
  • Dimension: Length 172.7 mm, body diameter 36.6 mm
  • Weight 170 g
  • Cable Length 5 feet, terminated with IP67 connectors

Cleaning & Calibration of the Pyxis ST-500 probe

The Pyxis ST-500 probe has a short fluidic channel. It can be easily cleaned. The fluidic and optical arrangement of the ST-500 probe is designed to overcome shortcomings associated with other fluorometers that have a distal sensor surface or a long, narrow fluidic cell. These fluorometers are susceptible to color and turbidity interference and fouling, and difficult to be cleaned.

Cleaning & Calibration