Sea-Bird Scientific HydroCycle-PO4 Phosphate Sensor

High accuracy in-situ phosphate measurement

Sea-Bird Scientific’s HydroCycle-PO4 is a wet chemical sensor engineered for environmental monitoring.  Advanced fluidics enable the sensor to stabilize rapidly and give accurate results once deployed without excessive priming. Real-time QC flags and post-processing enable fast, valid, scientifically defensible results that lead to better management recommendations.

  • Unattended
  • Phosphate
  • 5-month reagent life, 2.3- μgP/L detection limit, click-in reagent cartridges, on-board NIST standard, >1500 samples/service, factory-calibrated
  • SDI-12


Data Reliability:
The HydroCycle filters were engineered to improve efficiency and limit clogging during sediment events.

  • Data Quality:
    Advanced fluidics, that are resistant to bubbles that plague wet chemical sensors, enable the HydroCycle to make measurements at high oxygen and greatly improves sensor uptime in these environments. Now users can expect greater than 90% uptime!
  • Data Quality Control:
    Spend less time analyzing data quality and more time analyzing what the data means. The HydroCycle includes real-time data control flags that can be output via SDI-12. Additional quality control analytics and statistics are available through the post-processing features in the software.”


Sea-Bird Scientific HydroCycle PO4 Manual
Sea-Bird Scientific HydroCycle PO4 Brochure
Water Quality Solutions Overview Video
Nutrient Monitoring Infographic
Chester River Nutrient Monitoring Article
In-Situ Nutrient Monitoring Article
Nutrient Monitoring App Note

Technical Data

Height (w/handle) 56 cm
Width 18 cm
Weight in air 6.8 kg (w/ reagents)
Weight in water 0.37 kg
Depth 200 m
Temperature *1 0 … 35 °C
Input 10.5 … 18 VDC
Current draw 3.0 A max; 115 mA avg
Data output RS-232 / SDI-12
Host Connector MCBH-6-MP
SDI Connector MCBH-8-MP
Sample rate 2 per hour
Data memory 1 GB
LED wavelength 870 nm
Pathlength 5 cm
Linearity equal or greater than 95% R2
Detection limit, three standard deviations of 18 MOhm water equal to or less than 0.0023 mg/L PO4-P
Quantification limit, ten standard deviations of 18 MOhm water equal to or less than 0.0077 mg/L PO4-P
Standard deviation of standard solution of 2.6 µM equal to or less than 0.0015 mg/L PO4-P
Range, nominal *2 0-0.3 mg/L PO4-P
Note: *1 Both storage and operating temperature for sensor and reagent cartridges.
*2 Higher range is possible (0 … 40 µM, 0 … 1.2 mg/L PO4-P) but is outside specifications
mg/L PO4-P refers to mg of atoms phosphorus per liter measured in the form of reactive phosphate.
ppm ~ mg/L, ppb ~µg/LSpecifications are subject to change without notice.