Pyxis Fluorometers and Inline Refractometers

Pyxis fluorometers measure the concentration of a fluorescent tracer (PTSA, fluorescein or fluorescent polymer) added to treatment chemicals, and the RT-100 Prism inline refractometer measures refractive index to give glycol or BRIX concentration. Both approaches serve the same purpose: confirming that chemical dosing in cooling tower and boiler systems is correct. The range runs from continuous inline probes to handheld field instruments. Mikron Proses (Üsküdar, Istanbul) provides application consulting on matching the instrument to the tracer in your chemical and to the type of measurement point.

Fluorescent tracers · PTSA · Fluorescein · Glycol concentration → Send us your requirement

For the wider picture, see the guides on cooling tower automation and handheld water analyzers.

Continuous inline monitoring: Little Dipper 2

The Little Dipper 2 is a single-channel fluorometer that installs directly in the process line and samples 24 hours a day. It uses solid-state LED and photodiode technology with no moving parts, measures 1-200 ppb PTSA or 1-100 ppb fluorescein, and connects to a controller (for example a WebMasterONE) through a 4-20 mA analog output. It runs on 8-30 VDC and is offered in a PVC (1-inch NPTF) or polypropylene (3/4-inch NPTF) body for pressures up to 6.9 bar and temperatures up to 50 °C. The Handheld Little Dipper in the same brochure is a portable version with AA batteries, IP67 protection and single-point (100 ppb) calibration for field verification.

Inline tee-type probe sensors: ST-500, ST-525, ST-540, ST-565T and ST-588 series

Unlike the Little Dipper 2, the Pyxis ST-5xx family are removable probe sensors that insert into a tee fitting. They share the same electronics platform with an isolated 4-20 mA analog output and an isolated RS-485 Modbus digital output (22-26 VDC supply; 12-36 VDC for the ST-540), and wireless calibration and diagnostics through the MA-WB or MA-CR Bluetooth adapter and the uPyxis app. They differ in the tracer chemical they measure and in housing material (CPVC/UPVC or 304 stainless steel).

ST-500 series: PTSA

The ST-500 series measures PTSA (pyrenetetrasulfonic acid) directly with a UV LED (365 nm excitation / 410 nm emission) in industrial cooling and process water. The basic ST-500 has a CPVC body, measures 0-200 ppb (extendable to 0-300 ppb through uPyxis) with ±1 ppb precision, and connects through the supplied ST-001 tee (3/4-inch FNPT). The ST-500RO works in a narrower, more sensitive range for reverse osmosis systems: 0-40 ppb, ±0.2 ppb. The ST-500SS offers the same measuring performance in a 304 stainless steel body with direct 3/4-inch FNPT threads and works up to 20 bar. The ST-500W is a 304 stainless steel sensor designed to drop into Walchem and alternative fluorometer tees (about 0.9-30 L/min flow range, 6.9 bar). The ST-500SS-T plugs into the Pyxis ST-009 stainless steel tee and can be removed without tools; it measures 0-500 ppb with ±1.0 ppb resolution and works up to 20 bar. The ST-500 series compensates automatically for color (up to 10 ppm iron) and turbidity (up to 150 NTU) with internal algorithms.

ST-525 series: fluorescein

The ST-525 series measures fluorescein (sodium salt, also called uranine) directly with LED light sources in boiler and process water. The ST-525 (CPVC, 0-60 ppb, ±0.2 ppb) and the ST-525SS (304 stainless steel, same range, 3/4-inch FNPT direct threads, 20 bar) are the basic models. The ST-525SS-T is a removable stainless steel sensor that fits the ST-007 (stainless steel) or ST-001 (CPVC) tee and works in the 0-60 ppb range (±0.2 ppb) for standard boiler feedwater applications. For higher concentrations such as boiler blowdown, the ST-525SS-HR-T version of the same body measures 0-500 ppb with ±1.0 ppb resolution. The manufacturer states that the sample should be pre-cooled to 49 °C or below.

ST-540 series: NDSA (research use)

Pyxis offers the ST-540 series for research and development of boiler water programs traced with the NDSA tracer. The ST-540A (UPVC, 0-500 ppb, ±1.0 ppb, 3/4-inch connection with an ST-001 tee) and the ST-540SS (304 stainless steel, same 0-500 ppb range, direct 3/4-inch FNPT threads, 20 bar) are the basic models. For applications that need a narrower, more sensitive range, the ST-540SS-N measures 0-20 ppb with ±0.1 ppb resolution. Boiler water or boiler feedwater samples must be cooled below 49 °C and supplied pressurized.

ST-565T series: tolyltriazole (TTA)

The ST-565T measures the concentration of tolyltriazole (TTA), a copper corrosion inhibitor used in cooling water systems, by UV fluorescence at 0.0-10.0 ppm (factory-set), with ±0.2 ppm precision. It has a CPVC body, runs on 22-26 VDC and fits the ST-001 tee (3/4-inch FNPT). The sister model ST-565 on the same platform measures HST (halogen stable triazole) at 0.0-7.5 ppm.

The manufacturer’s datasheet states clearly that this technology is not a wet chemistry test and that results can vary with water quality: other organic matter in the water can give a false high reading through UV fluorescence or absorbance, the device does not distinguish azole species or reacted from unreacted azole, and it does not work in nitrite-treated water because nitrite absorbs UV light and gives a false high result. With these limits understood, the manufacturer states that the ST-565 and ST-565T are commonly used for quick azole verification, but that systems with surface-water makeup or a high organic load may not be suitable because of the interference risk.

ST-588: PTSA + tagged polymer (dual-channel combined sensor)

The ST-588 measures PTSA and a fluorescent tagged polymer independently in one body: the PTSA channel works at 365/410 nm and the polymer channel at 410/450 nm. PTSA is measured at 0.0-200.0 ppb (expandable to 500 ppb through uPyxis) and the fluorescent tagged polymer at 0.0-20.0 ppm, with a stated polymer precision of ±0.1 ppm (3 sigma). The sensor provides 2 isolated 4-20 mA outputs, one per parameter, plus an isolated RS-485 Modbus output on one 8-pin cable, and uses 2 W on 22-26 VDC. The ST-588 has a CPVC body (with quartz optical windows) rated for 6.9 bar and 40 °C; the ST-588SS gives the same measuring performance in a 304 stainless steel and quartz body at up to 20 bar. The manufacturer states that the polymer scale is calibrated for a polymer containing 0.25 mole % fluorescent monomer, and that typical polymer properties may vary between producers.

Handheld field instruments: Pyxis SP series

• SP-350P and SP-380P are handheld fluorometers with a built-in sample cell, so no cuvette is needed. The SP-350P is single-channel (fluorescent polymer, 0.1-20 ppm); the SP-380P is dual-channel and measures PTSA (0-300 ppb) and fluorescent polymer (0.1-20 ppm) at the same time. Both compensate for sample color and turbidity.
• SP-380 is a dual-channel handheld fluorometer that measures PTSA (0-300 ppb) and fluorescein (0-600 ppb).
• SP-910 is a combined photometer and fluorometer: colorimetric measurement at 7 LED wavelengths (for analytes such as chlorine, phosphate, iron and copper), PTSA fluorescence (0-300 ppb) and nephelometric turbidity (0-200 NTU), with a wide list of supported colorimetric methods.
• SP-710B measures PTSA (0-300 ppb), conductivity, pH and temperature in one handheld instrument, and connects to the uPyxis app over Bluetooth.
• SP-200 OXIPOCKET is a pocket colorimeter and fluorometer for oxidizing disinfectants; its direct-reading bleach methods cover sodium hypochlorite from 0.015 to 16 percent.
• A handheld LPR corrosion tester also belongs to the Pyxis range for on-site measurement of corrosion rate and the localized (pitting) corrosion index on steel, copper and brass.

Inline refractometer: RT-100 Prism

The RT-100 Prism measures refractive index instead of using a fluorescent tracer: it measures 1.31700-1.5100 with ±0.0002 accuracy and, through built-in temperature-dependent equations, converts the value directly to %BRIX, %MEG (mono-ethylene glycol), %MPG (mono-propylene glycol) or %ALV (Advanced Low Viscosity heat transfer fluid) concentration. With its 316L stainless steel body and sapphire measuring surface it can also work in dirty or turbid streams. It is installed in a Tri-Clamp flow cell and works at up to 0.98 MPa sample pressure and 70 °C sample temperature, and a 2 × 4-20 mA and RS-485 Modbus output connects it to any controller, PLC or DCS network. With the uPyxis app and the MA-CR Bluetooth adapter, air calibration, offset calibration and transfer of up to 56 days of history (1 reading per minute) are possible. For other Pyxis refractometers see the RT-110 series, the RT-200 and the RT-50.

Which instrument for which tracer

The choice depends on which fluorescent tracer (PTSA, fluorescein or fluorescent polymer) the chemical carries and on the type of measurement point, continuous inline or periodic field verification; for glycol or BRIX-based concentration monitoring, the refractive index principle of the RT-100 Prism applies. Send us your requirement and we will select the right instrument and tracer combination together.