conductivity (EC), temperature & depth


The HYDROS-21 sensor is a low cost, accurate tool for monitoring of water level, electrical conductivity, and temperature in both ground water and surface water.  The sensor utilizes a vented pressure transducer to obtain accurate water level measurements from 0 to 10 m while removing the effects of barometric pressure.  With a range of 0 to 120 dS/m, the CTD sensor has the ability to make accurate electrical conductivity measurements in a broad range of applications.

The HYDROS-21 sensor is a robust, marine grade sensor, 3.4 cm in diameter. It connects by cable to an external data logger. Much of the complex circuitry is in the data logger, lowering the cost of individual sensors without impacting their accuracy or resolution.  This makes it so that instead having to rely on a single measurement, you can measure in several different locations without exceeding your budget.

The CTD sensor is compatible with our range data loggers. The ES-SYS range of data logging systems offers a remote transmission option to deliver data wirelessly to your desktop. With this option, water depth, temperature, and electrical conductivity can be monitored from any internet-connected computer in near-real time.

  • Aquifer recharge and recovery.
  • Saltwater intrusion, desalination, and wastewater.
  • Wetland monitoring.
  • Groundwater contamination monitoring.
  • Surface water monitoring.


  • Robust marine-grade epoxy overmold to resist corrosion in tough environments.
  • Compact 3.4 cm diameter sensor body to fit into tight spaces.
  • External logger with remote transmission option to deliver data to your desktop.
  • Permanent connection allows you to collect data continuously without pulling up the sensor.
  • Low per-sensor cost.


whole system monitoring solutions

Sap Flow MeterEdaphic Scientific is a one-stop shop for a whole system monitoring solution. We provide plant and soil monitoring systems for researchers and growers.

Our systems not only support HYDROS-21 CTD sensors, but related sensors such as dissolved oxygen, dissolved CO2, dissolved CH4, dissolved H2S, pH, drainage, soil moisture, weather parameters, and more.

At Edaphic Scientific we want to work with you from the start of your project through to its completion. We can provide:

  • Assistance with project and experimental design
  • Procurement of all monitoring equipment, including sensors, data loggers and data management software. Edaphic Scientific is a one-stop shop where we can source and find any necessary equipment for your project from our preferred suppliers or third party suppliers
  • Installation and training
  • On-going assistance with data interpretation and equipment maintenance
  • Data correction and analysis, including statistical analysis with the R-package
  • Report and publication preparation including tables, figures, graphs, and manuscript writing


advanced data collection and management solutions

Edaphic Scientific recognises the need for flexible and adaptable sensor and data logging solutions for experimental or environmental monitoring projects.

Data can be downloaded directly in the field from data loggers. A direct connection between the data loggers and your computer, via a USB cable, can be used for manual downloading of data.

Alternatively, data can be downloaded over the internet on your iPhone, iPad or desktop computer with the Eagle.io cloud-based, data management software solutions. Through this remote based downloading capabilities, you can download, view and manage your data, and system, anywhere in the world and at anytime.


feature specification
measurement specifications
Water Depth Range: 0 - 10,000 mm Resolution: I mm Accuracy: ±0.25% of full scale at 20 °C NOTE: Depth measurement accuracy assumes no abrupt temperature variations
Temperature Range: -40 to +60 °C Resolution: 0.1 °C Accuracy: ±1.0 °C NOTE: The pressure transducer may be damaged or destroyed if frozen in ice. Remove the sensor if the water temperature could drop below 0°C (32 °F).
Bulk Electrical Conductivity (EC) Range: 0 - 120 dS/m Resolution: 0.001 dS/m Accuracy: ±0.01 dS/m or ±10%, whichever is greater NOTE: The EC measurement is corrected to a standard temperature of 25°C.
communication specifications
Output DOI serial or SDl-12 communications protocol
Data Logger Compatibility METER ZL6 data loggers and any data acquisition system capable of 4.0- to 15.0-VDC power and serial or SDl-12 communications
physical specifications
Dimensions Diameter: 3.4 cm (1.3 in) Length: 9.0 cm (3.5 in)
Operating Temperature Range Minimum: 0 °C Maximum: 60 °C NOTE: Sensors may be used at higher temperatures under certain conditions; contact Customer Support for assistance.
Cable Length 10 m (standard) 20 m 40 m (maximum cable length)
Cable Diameter 6.00 ±0.25 mm (0.240 ±0.010 in) with minimum jacket of 0.80 mm (0.031 in)
Connector Types Stereo plug connector or stripped and tinned wires
Stereo Plug Connector Diameter 3.5 mm
Conductor Gauge 20-AWG signal and power/ 21-AWG ground wire
Supply Voltage (Power to Ground) Minimum: 4.0 V Typical: NA Maximum: 15.0 V
Measurement Time 450 ms (milliseconds) typical

manual & docs

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