Live Webinar: HL7 – A NEW Smart Platform for Better Data


Live Webinar Thursday, October 26, 2017 11:00 am Eastern Time / 17:00 pm Berlin Time

The HYDROLAB HL7 multiparameter sonde offers a versatile, durable and practical solution to the day to day needs of monitoring programs for both simple and complex deployments. With a large sensor suite, it is able to thrive in demanding environmental conditions for long term continuous and profile monitoring.  It helps our customers to correctly log data autonomously and easily integrate into real time telemetry systems.


HYDROLAB Operating Software

  • Simple and intuitive guided software
  • This powerful software tool helps to make better decisions, minimize errors, and increases efficiency in the lab and on the deployment site.

Webinar Agenda:

  • Improve efficiency with streamlined setup & calibrations: Log files, data collection and guided calibrations
  • Traceable data you can trust: Calibration logs, leveraging metadata for data quality, and HYDROLAB HL7 Operating Software
  • Experiences from the field: Long-term field deployments and extreme depth profilingFind out more during our live webinar. Includes LIVE Q&A SESSION


Hydromet Launches new HYDROLAB HL7 Water Quality Sonde

OTT Hydromet introduces the HYDROLAB HL7 multiparameter sonde for continuous monitoring of 9 key water quality parameters in open natural waters. This new multi-parameter probe maximizes deployment life, minimizes maintenance and provides traceable data you can trust.


The HYDROLAB HL7 includes intuitive software for unmatched usability, exceptional power performance and proven sensor options, all delivering high data quality and reliability.

Learn More about the new Hydrolab HL7 Sonde – click here
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Multiparameter Water Quality Instrument Selection Guide


HYDROLAB®, Sea-Bird and OTT offer a variety of multiparameter water quality instrumentation and nutrient sensors for long-term applications. Sea-Bird Scientific water quality multiparameter sondes are developed to provide accurate data in environments with salt water and biologically rich environments.Developed for longterm deployments. Learn more about our water quality instruments and which one works best for you.

What you will learn in the guide:

  • Water quality instruments available from OTT, HYDROLAB®, and Sea-Bird
  • Best application fit by technology
  • Available parameters
  • Use models
  • Monitoring examples

Click to get your Multiparameter Water Quality Instrument Selection Guide




Download the Quality Assurance and Quality Control Technical Note Now!

The primary activities taken to assure and control data quality are aptly called quality assurance and quality control. Determining the “true value” of a water quality measurement is an important fundamental of any QA/QC program. To determine the true value, many professionals apply a second means of measuring the parameter of interest, such as another instrument that is kept serviced and calibrated just for quality control purposes or a grab sample that is evaluated using a trusted laboratory technique. Instruments such as HYDROLAB‘s produce high quality data for many applications and by leveraging the HYDROLAB Operating System you can maximize uptime with streamlined calibration tasks

Good QA/QC programs require robust calibration procedures that ultimately provide valuable information about, and confidence in, the instrument’s performance. The QA/QC Tech note highlights key information made available during a HYDROLAB multi-parameter water quality sonde calibration.

Read the complete QA/QC Tech Note

The Hydrolab Sonde Survivor Contest is Back!

Our popular Hydrolab Sonde Survivor Contest has returned in 2015! The Hydrolab Sonde Survivor Contest is a celebration of the harsh and unique deployments that Hydrolab multiparameter instrumentation is put through around the world.

Enter your Hydrolab story by Friday, December 11th and you could win a new Hydrolab HL4 multiparameter sonde and SurveyorHL handheld!

The winners from the 2014 contest with their new Hydrolab HL4 and SurveyorHL.



pH Measurements in Environmental Water Quality Monitoring

pH measurement in natural aquatic environments is commonly done electrochemically by measuring the voltage between a pH-sensitive glass electrode and a reference electrode. Commercial pH meters convert voltage readings into pH units using calculations based on the Nernst equation and sometimes other assumptions about the environment and measurement system. Because of unavoidable differences between theoretical pH measurement systems and real-world pH measurements systems, pH is often said to be defined “operationally” based on an accepted electrochemical method such as Standard Method 4500-H+ or similar methods from other standards organizations. Despite pH sensor imperfections, most water resource professionals accept measurements derived from glass electrode measurement systems as the “operational definition” of pH and use them for meaningful and defensible scientific endeavors.

hydrolab ph sensor

A Hydrolab pH sensor for use on Hydrolab multiparameter sondes.

The millivolt reading from a theoretically perfect pH sensor in a pH 7 solution is zero. In nominal pH 4 and pH 10 buffers at 25 °C, millivolt readings are 177.48 and -177.48, respectively. In practice, millivolt readings will differ in an amount referred to as the asymmetry potential of the electrode. As the electrodes age and degrade with use, mV readings during calibration will change – decreasing in acidic solutions and increasing in basic solutions.

Changes in mV readings observed during calibration procedures over time can be used as an indicator of electrode condition and the quality of the calibration procedure. Small deviations from theoretical mV readings or historic readings are not a concern because they are corrected during the calibration process and are generally stable between calibration events. Additional confidence in the calibration can be built by performing a linearity check. This is done by placing the sensor in a third reference standard (different from the two used in calibration) and comparing the reading to the expected reading.

Reading mV directly could allow the user to derive a unique mathematical equation relating voltage to pH that is different from the one used in the pH meter. Deriving a unique equation has little purpose for most water monitoring plans.

To incorporate pH-mV output into a quality assurance program:

  • Follow best practices for pH calibration procedures, considering the goals and constraints of a water quality monitoring program
  • Record the mV reading during calibrations in a calibration log or laboratory notebook
  • Watch for sudden changes from prior calibrations to indicate there was an error or change in the calibration procedure, incomplete maintenance, or sensor damage
  • Use large deviations that develop with time along with slow response times or erratic readings as an indicator that measuring electrode or reference electrode needs to be regenerated or replaced.

Published guidelines on acceptable mV readings or slope percents vary. Rather than relying on absolute values of mV or slope to determine sensor quality, it is best to incorporate the data to a comprehensive QA/QC program where it can be used to assess overall sensor, calibration, and data quality.

For more information, please contact OTT Hydromet Technical Support.

What is pH and How is it Measured: A Technical Handbook for Industry by Frederick J. Kohlman. Hach Company 2003
The Sometimes Maddening Science of pH Measurement by Richard Presley. American Laboratory News June 1999.
Standard Methods for the Examination of Water and Wastewater

Turbidity Measurement: Why Does it Matter?

Turbidity is one of the most talked about parameters in environmental water quality monitoring, yet the details around turbidity measurement are not always known or fully understood. Use our guide below for a better understand of all things turbidity!

Turbidity Overview

The amount of dispersed suspended solids in natural water bodies is an important indicator of water quality. These solids (such as silt, clay, algae, and organic matter) obstruct the transmittance of light through water and create a qualitative characteristic known as turbidity. Turbidity is often closely correlated to climatological or surface water conditions, and therefore indicates changes in environmental conditions of lakes, rivers and streams. For example, high levels of suspended sediment can interfere with photosynthesis by blocking light from reaching aquatic plants. This not only damages vegetation but also results in reduced levels of dissolved oxygen because of the reduction in photosynthesis. Moreover, waters with high levels of suspended solids absorb more light, which can cause an increase in water temperature, creating even lower dissolved oxygen.  This stresses aerobic aquatic organisms and could ultimately lead to fish kills.

Turbidity as a Valuable Surrogate

The Clean Water Act requires States to establish total maximum daily loads (TMDLs) of various pollutants to meet water quality standards. The ability to continuously measure water parameters associated with impairments is often limited by technical and financial constraints. Turbidity, however, can be effective as a surrogate measurement because it can be measured in-stream on a continuous basis and it is strongly correlated with sediment, nutrients, and bacteria concentrations.  Below is a list of turbidity as a surrogate measurement for many environmental influencers:

  • Monitoring the impact of humans on natural water bodies.
  • Monitoring pathogens in water, such as E.coli in storm water runoff from cattle pastures.
  • Monitoring sediments to track erosion and landscape change.
  • Monitoring natural streams below mining and dredging operations
  • Measuring total phosphorous in water is very difficult, but an increase in phosphate or phosphorous typically correlates to an increase in turbidity levels.
Turbidity measurement with the Hydrolab HL4 multiparameter sonde.

Turbidity measurement with the Hydrolab HL4 multiparameter sonde.

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Phytoplankton Measurement with Fluorometers


Phytoplankton measurement is key for understanding the health of an aquatic ecosystem in both freshwater and saltwater environments.

Measuring phytoplankton can provide valuable insights regarding the biological status of any given aquatic system. Some common applications include:

Primary Productivity Quantification
As phytoplankton form the foundation of aquatic food webs, concentrations of phytoplankton can have a direct effect on all organisms higher up on the food chain. Quantifying primary production through phytoplankton biomass measurements is a common way to gather direct insights on the baseline energy available within any given aquatic food web.

Eutrophication / Nutrient Status Monitoring
Eutrophication is the process where nutrients such as nitrogen and phosphorous are loaded into an aquatic system, typically caused by watershed run-off inputs. Eutrophic systems are highly prone to phytoplankton blooms which can lead to dissolved oxygen depletion when phytoplankton cells die off. Phytoplankton monitoring can help water resource managers to control watershed inputs that can affect nutrient loading within aquatic systems.

Harmful Algal Bloom (HAB) Monitoring
Certain species of phytoplankton, mainly cyanobacteria, can release toxins that can cause adverse health effects to humans and animals. Continuous monitoring of phytoplankton levels as part of a broad management plan can help water quality managers to decrease the prevalence of health incidents due to harmful algae.

Drinking Water Management
Certain species of phytoplankton can produce compounds that create taste and odor issues in water, including the compounds 2-MIB and geosmin. Proactive phytoplankton monitoring can provide data that helps managers determine when and where to apply algaecide, as well as which source water intakes to pull from in order to minimize the biological load entering a treatment system.

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Choosing the Right Groundwater Level Logger

Identifying the best level logger for your groundwater monitoring application can be a complex task with many different technologies available that are best suited for a variety of different measurement goals.

The most critical information to gather as you start your selection search are the physical characteristics of your groundwater well and the approximate depth-to-water range.

While all groundwater loggers measure level, some have the capability to measure water quality parameters like  conductivity, salinity, and total dissolved solids (TDS) as well. These parameters are useful in saltwater intrusion studies in aquifers or also to monitor the impact of man-made activities on groundwater supplies.

A final and important item to consider is the remote data communication (telemetry) element. Remote data communication from a groundwater logger can send updates hourly, daily, or weekly and can limit the number of required field visits to service the well. A variety of transmission technologies are available, though some (like GSM / GPRS) can be limited by the signal strength in your well area.

Click here to read the full OTT Hydromet Groundwater Sensor Selection guide, or see the review the image below for a list of groundwater logger considerations.

GW Parameters