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ST-525 Series Inline Fluorescein Sensors
- Product Details
- Specifications
- Boilers & Process Water
ST-525 Series Inline Fluorescein Sensors
The Pyxis ST-525 Series measures fluorescein directly in the water line. Fluorescein (also known as uranine) is a fluorescent tracer used in water treatment, so a continuous reading shows how much treatment is actually in the system.
The sensor uses LED light sources and Pyxis’s own algorithms to measure the tracer, while extra optical channels check the colour and turbidity of the sample and correct the reading for them. Isolated 4–20 mA and RS-485 Modbus outputs connect it to any controller, PLC or DCS, and with the MA-WB Bluetooth adapter it can be checked and calibrated from the uPyxis app.
Three Models
- ST-525: CPVC body fitted in the ST-001 inline tee, 0–60 ppb, up to 6.9 bar (100 psi)
- ST-525SS: stainless steel body with ¾” FNPT ports, 0–60 ppb, up to 20 bar (290 psi)
- ST-525SS High Range: stainless steel, 0–500 ppb, for higher tracer levels such as boiler blowdown
Built-in Cleanliness Check
The sensor measures how much light is lost through its optical channel, so it knows when it is getting dirty. A cleanliness check in the uPyxis app shows whether the sensor needs cleaning before calibration, and confirms afterwards that the clean has worked.
ST-525 Series Specifications
| Item | ST-525 | ST-525SS | ST-525SS-HR |
|---|---|---|---|
| Part Number | 50665 | 50666 | 50915 |
| Measures | Fluorescein (sodium fluorescein / uranine, CAS 508-47-8) | ||
| Range | 0 – 60 ppb | 0 – 60 ppb | 0 – 500 ppb |
| Resolution | ±0.2 ppb | ±0.2 ppb | ±1.0 ppb |
| 4–20 mA Output Scale | 0 – 60 ppb | 0 – 60 ppb | 0 – 500 ppb |
| 4–20 mA Span | 20 mA point can be set lower in the uPyxis app | ||
| Interference Compensation | Automatic colour and turbidity compensation | ||
| Diagnostics | Optical cleanliness check, via uPyxis app or Modbus | ||
| Calibration | Two-point (zero and slope) against DI water and a fluorescein standard, or online against a measured sample | ||
| Calibration Standard | 10 – 60 ppb | 10 – 60 ppb | 250 – 500 ppb |
| Outputs | Isolated 4–20 mA and isolated RS-485 Modbus RTU, 7-pin connector | ||
| Wireless Access | Bluetooth with MA-WB adapter or PowerPACK, uPyxis mobile and desktop app | ||
| Power Supply | 22 – 26 V DC, 1 W | ||
| Installation | ST-001 inline tee, ¾" FNPT thread and socket (supplied) | ¾" FNPT ports in the sensor body | ¾" FNPT ports in the sensor body |
| Body Material | CPVC | 304 stainless steel | 304 stainless steel |
| Maximum Pressure | 6.9 bar (100 psi) | 20 bar (290 psi) | 20 bar (290 psi) |
| Operating Temperature | 4 – 49 °C (40 – 120 °F) | ||
| Storage Temperature | -20 °C to 60 °C (-4 °F to 140 °F) | ||
| Dimensions | 172.7 mm long × 36.6 mm diameter (6.8 × 1.44 in) | ||
| Weight | 170 g (0.37 lb) | 1,148 g (2.5 lb) | 1,148 g (2.5 lb) |
| Cable | 1.5 m (5 ft) bulkhead cable with IP67 adapter, plus 0.45 m (1.5 ft) flying lead | ||
| Enclosure Rating | IP67 | ||
| Approvals | CE, RoHS | ||
Ideal for Boilers & Process Water
The ST-525 Series is designed for industrial boiler and process water treatment. The standard 0–60 ppb models suit boiler feedwater, and the 0–500 ppb high range model suits boiler blowdown. The stainless steel models take the higher pressures of boiler lines; the sample must first be cooled to below 49 °C.
Key Features
- Direct fluorescein (uranine) measurement with LED light sources
- 0–60 ppb, or 0–500 ppb in the high range model
- Automatic colour and turbidity compensation
- Cleanliness diagnostics show when the optics need cleaning
- Isolated 4–20 mA and RS-485 Modbus outputs
- Bluetooth calibration and diagnostics in the uPyxis app (with MA-WB adapter)
- Two-point calibration, or online against a sample measured with a handheld fluorometer
- CPVC body to 6.9 bar, or stainless steel to 20 bar
- Low power: 24 V DC, 1 W
- IP67; CE and RoHS
