Hydrolab HL4 Multiparameter Sonde

New Hydrolab Platform: Reliability, Ease-of-use, Metadata

The Hydrolab HL4 is the next generation multiparameter water quality sonde from OTT Hydromet.  Know the instrument is working correctly and troubleshoot quickly. Streamline calibration tasks and produce valid, scientifically defensible conclusions.

Use with the Hydrolab Surveyor HL for attended monitoring, or for unattended continuous monitoring applications, the HL4 has on-board data logging and dedicated communications modules for easy integration with external loggers and telemetry.

 Hydrolab HL4 Intro Video 

  • Attended, Unattended
  • Temperature, Conductivity, Depth, pH, Dissolved Oxygen (LDO), Turbidity, ORP
  • The next generation multiparameter water quality instrument
  • SDI-12, RS-485, RS-232, TTY, USB


Self-monitoring system reports the status of the instrument, flags the data, and shows the user where the problem is with assistance on how to solve the issue

  • User-scheduled calibration and maintenance intervals indicate when they are due
  • Guided and semi-automated calibration routines lead the user through the calibration process
  • Calibration results are stored with date and time, calibration type, user identification, and user notes
  • Check Calibration process allows the user to verify calibration and store the results
  • Calibration reports contain information about previous calibrations and calibration checks
  • Sensor status is saved with every line of data and is contained in the log file
  • Dedicated communications modules allow easy integration with data loggers and telemetry systems
  • Compatible with the Surveyor HL – a fully IP67 handheld designed for field use with a full-color screen that is visible in direct sunlight

Examples of Use

For measurement of popular water quality parameters in:

  • Freshwater rivers and streams, lakes and reservoirs, and groundwater wells
  • Salt or brackish water bays, estuaries, and near-coastal areas
  • Attended monitoring, continuous unattended and real-time monitoring

Technical Data

Sensors Temperature sensor and up to four additional sensors plus depth and ORP
External 6 … 30 VDC (12 VDC nominal) applied to the communications module,
12 VDC: 250 mW average, 19 W peak
Internal (Optional) Internal alkaline D-cell battery, non-rechargeable.
Sleep mode at 12 V 20 mA
Communications Hydrolab communications modules: USB, SDI-12, RS232, RS485, or TTY
Memory 4 GB of internal memory; 1 second interval minimum
User Interface
PC Software Hydrolab Operating Software
Handheld (Optional) Hydrolab Surveyor HL
Sonde Depth Rating 200 m (656 ft)
Maximum Deployment Cable 200 m (656 ft)
Diameter w/o bumpers 4.4 cm (1.75 in.)
Diameter with bumpers 5.3 cm (2.1 in.)
Weight with internal battery pack (IBP) and storage/calibration cup 2.2 kg (5 lb)
Length – no IBP, standard sensor guard 51.4 cm (20.25 in.)
Length – no IBP, extended sensor guard 66.4 cm (26.125 in.)
Length – IBP and standard sensor guard 62.2cm (24.5 in.)
Length – IBP and extended sensor guard 77.8 cm (30.625 in.)
Environmental conditions
Operating temperature -5 … 50 °C (23 … 122 °F), non-freezing
Storage temperature 1 … 50 °C (34 … 122 °F)




Sensor Firmware

Click here to visit the download site for Hydrolab sensor firmware


Hydrolab Standard Methods Sheet
Leaflet – Multiparameter-Sonde Water Quality Hydrolab HL4
Water Quality Solutions Overview Video
Hydrolab Operating Software
Hydrolab Operating Software 32 bit install
Hydrolab Operating Software
Hydrolab Operating Software 64 bit install
Hydrolab HL4 Comm. Module Manual
Hydrolab HL4 Sensor Manual
Hydrolab HL4 Manual
QA QC White Paper
Hydrolab HL4 Reviews
Hydrolab HL4 Reviews
Turbidity White Paper
Turbidity White Paper
Leaflet Hydromet Cloud EN
Hydrolab HL4 Overview Video
Hydrolab HL4 Overview Video