Pyxis ST-500

Real-time PTSA monitoring of inhibitor dose with its extreme accuracy and proven robustness

The ST-500 Series inline sensor platform is a proprietary design for the direct measurement of PTSA (Pyrenetetrasulphonic Acid, CAS# 59572-10-0) ultilsing LED UV light sources (365nm ex/ 410nm em) for use in industrial cooling water and process treatment applications.


The ST-500 series offer Pyxis Lab® proprietary algorithms to determine the concentrations of PTSA while measuring sample turbidity and colour in highly contaminated waters (i.e. ≤150NTU and 10ppm Fe) for internal compensation. The ST-500 series offers a combination of 4–20mA as well as RS-485 Modbus output signals and is Bluetooth® enabled for wireless cleanliness diagnostics and calibration when used with the MA-WB or PowerPACK Series of Bluetooth® adapters and the uPyxis® mobile and desktop app.

The ST-500 Series is provided in CPVC with the standard Pyxis Lab® ST-001 inline 3/4in FNPT tee assembly, 5ft bulk-head cable with quick adapter and 1.5ft flying lead cable with quick adapter, enabling rapid wiring to any microprocessor controller, PLC or DCS system. The ST-500SS is offered in 304L Stainless Steel with 3/4in FNPT ports for high pressure applications.


The ST-500 is now available in a new model for compatibility with existing industry known tee assemblies.

The ST-500W fits perfectly into WALCHEM® and other industry-known tee assemblies.

Product information



Product Range

ProductOutput ScaleMax rangeAccuracyInstallation
0-200 ppb
0-300 ppb
±1 ppb
ST-001 tee inc
0-200 ppb
0–300 ppb
±1 ppb
3/4inch FNPT
ST-500 SS
0-200 ppb
0-300 ppb
±1 ppb
3/4" thread
ST-500: CPVC
Low cost CPCC contacting sensor
ST-500SS: Steel
Toroidal non-contacting PEEK sensor
ST-500W: Walchem compatible
Low cost CPCC contacting sensor
ST-100: Tee
Low cost CPCC contacting sensor

Typical applications

For use in industrial cooling water and process treatment applications.

Related products

  • Pyxis ST-500 Inline Sensor

    PTSA & tagged polymer
    Dual inline sensor for industrial cooling water applications

  • Pyxis ST-590 Inline Sensor

    Tagged polymer
    Inline sensor for industrial cooling water applications

  • Pyxis ST-590 Inline Sensor

    PTSA & turbidity
    Utilising both LED UV and warm white light sources

  • Pyxis HM-500

    Oil in water
    Measures for oil in water at a range of 0-10ppm

You may also need...

  • Intuition-9
    Powerful control with 24 inputs & 12 outputs

  • Intuition-6
    Remote communication with 4 inputs & 6 outputs

  • W100
    1 sensor input & 3 control outputs, wall mount design


  • PTSA Calibration Solutions

    PTSA Calibration Solutions
    Calibrate quickly. Ensure accuracy.

  • Dosing tanks and bunds

    Dosing tanks & bunds
    Round or rectangular in a range of capacities from 25 to 1,000 litres.

  • Pyxis MA Series

    MA Series
    Inline BlueTooth® 5.0 wireless adapters

  • Pyxis MA Series

    Pyxis PowerPACK series BlueTooth® auxiliary adapters



Custom build solutions

Redefine simplicity and flexibility in cooling tower solutions with our plug-and-play service that delivers rapid installation.

We offer standard layout that serves as a solid foundation but we can be customise to meet the unique needs of any client site. We tailor the build to achieve optimal performance.

Our custom builds are popular as a comprehensive solution that's wired and seamlessly integrated meeting any site requirements. Email us today to learn more about our bespoke custom built solutions to speed up your installation and reduce operation or project downtime.


We specialise in delivering tailored product training to empower your team and enhance operational efficiency. Whether you prefer on-site sessions, at your company's location or the convenience of video conferencing, we've got you covered.

Our focus revolves around installation best practices, ensuring seamless product connectivity, and optimising maintenance procedures. Take the first step towards maximising your team's potential. Email us today to learn more about our bespoke training offerings, check availability, and embark on a journey to enhance your team's expertise.

Request support

Follow us on LinkedIn

Sensys Ltd

Head Office
24 Vision Park
Preston Place
Upper Caldecote
SG18 9GQ

what3words: ///uptown.wisley.guests

01438 759 595

Join our mailing list

Sensys icon

Enquire Now