Pyxis EM-500 Chlorophyll-a Sensor

The Pyxis EM-500 is an inline sensor that measures the fluorescence of chlorophyll-a, the primary photosynthetic pigment of living algae cells, to assess the living algae biomass of bulk water in real time. It is an LED fluorometer that works at 470 nm excitation and 675 nm emission. Mikron Proses (Üsküdar, Istanbul) provides application consulting on algae monitoring with the EM-500 and its higher-range sister model, the EM-510.

Algae monitoring · Cooling tower and process water → Send us your requirement

For the measurement background, see the guide on chlorophyll sensors and the overview of cooling tower automation.

Measuring principle and interference compensation

The fluidic and optical arrangement of the EM-500 is designed to overcome the typical weaknesses of other inline fluorometers: the sensor automatically compensates for color in the sample water (up to 10 ppm as iron) and for turbidity (up to 150 NTU). The EM-500 measures from 0.1 to 50 ppb (±0.2 ppb in the manufacturer’s table). The EM-510 (P/N 50502), offered on the same platform for more concentrated applications, works from 0 to 500 ppb (±1 ppb).

Outputs, installation and maintenance

The EM-500 can be connected to any controller that accepts an isolated or non-isolated 4-20 mA input, or to an RS-485 Modbus network. It is installed in the process line with the supplied ST-001 inline tee (3/4-inch NPT thread and socket union) and works at sample flows of about 0-30 L/min. Supply is 24 VDC and power consumption is about 1 W. Operating pressure is up to 0.7 MPa at 40 °C; operating temperature is 0-40 °C and storage temperature is -20 to 60 °C. The UPVC sensor is 172 mm long and 36.6 mm in diameter, weighs 170 g, and comes with an IP-67 waterproof connector and 1.5 m bulkhead and 1.5 m flying lead 7-pin cables. The manufacturer states a typical service life of 2-3 years.

The short fluidic channel of the EM-500 can be cleaned easily as described in the sensor cleaning and maintenance section of the manufacturer’s operation manual, and sensor cleanliness can be diagnosed in the uPyxis mobile or desktop app. When powered through an MA-WB (7-pin) or PowerPACK series Bluetooth adapter, the sensor can be reached wirelessly in the uPyxis app, which shows the chlorophyll-a value as a live graph and offers a sensor cleanliness check and calibration function. The manufacturer recommends cleaning and calibrating EM-500 series sensors at least once a month; in clean water this interval can be extended, while heavily contaminated applications may need more frequent diagnosis, cleaning and calibration. Calibration is done with the matching Pyxis calibration standard, for example CHLORO-20.

Send us your requirement for help choosing between the EM-500 and EM-510 for your water.