H2O Lab-News

Save yourself time and effort.  Get accurate O2 measurements!

Dissolved oxygen is a critical control parameter in many applications: in wastewater treatment influencing plant efficiency, in surface water monitoring and fish farming indicating water quality, and in multiple production processes affecting e.g. product shelf-life.

Measuring dissolved oxygen with a Clark electrode has been a standard method for decades and it has its challenges: polarisation time, frequent re-calibration, drift, interferences and a lot of maintenance effort.

In 2003 HACH LANGE was the first to introduce a solution to these issues, which has since revolutionised the market: Optical oxygen measurement with the LDO sensor!

LDO stands for Luminescent Dissolved Oxygen. The amount of O2 is determined using a layer sensitive to oxygen that is excited by blue light. It emits red light back, an effect that is termed luminescence. The time between excitation and the red light emission is determined by the oxygen concentration in the sample.

1 LED, 2 Reference LED, 3 Photodiode

The more dissolved oxygen there is in the sample, the shorter the time it takes for the red light to be emitted.

Read on to find out how LDO can make your daily work easier!

How to measure dissolved oxygen efficiently and easily

LDO is definitively the best technology to measure DO, whether in the field, lab or online. It combines quality of results and ease of use with low maintenance.
  • A typical wastewater treatment plant with 12 oxygen sensors may save approx. 200 hours of maintenance and calibration per year!
  • No replacement of electrolyte, no interference by deposits or H2S
  • Flow-free sensor without oxygen consumption ensures precise and accurate measurements at over the whole measuring range
  • Intelligent INTELLICAL technology features an automatic reminder to change the sensor cap each year ensuring error-free results with minimum effort.
  • With LDO technology there is no more waiting time for the electrode to polarise. The INTELLICAL sensor is plugged into the instrument and ready to go! The robust HQD meters are available in single or dual channel versions ready to also measure pH, ORP and conductivity.

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Literature to support you in your daily work.

  • With LDO and HQD meters it is now possible to monitor the oxygen content at various measurement locations with the same instrument, e.g. in barrels, tanks and bottles.
  • Click here to download the PDF file

HACH LANGE solutions deliver a perfectly coordinated system for lab and process analysis.

To request more information please fill out the form at the top of the page.
INTELLICAL LDO sensors for portable and lab use

Sensors available in standard laboratory and rugged outdoor versions with cable lengths from 1 to 30 metres.
  • Precise and accurate measurements over the whole measuring range
  • Can be connected to any HQ30D / HQ40D portable meter and HQ430D / HQ440D benchtop meter.

Request more information now!

HQD portable and benchtop meters with digital INTELLICAL electrodes

  • Easy to use, no matter where you use it.
  • HQD’s user friendly meters allow even new operators to produce accurate measurements while reducing possible errors, saving you time and hassle. Additionally, the durable design is built to handle the toughest conditions, in both the field and the lab.
  • Automatically detect the testing parameter and calibration history
  • Large graphic display makes the results easy to read, even in difficult light conditions
  • Mix and match of electrodes and meters ensures reliability and flexibility


Request more information now!

Classic polarographic oxygen electrodes

Classic Clark electrodes with replaceable oxygen permeable membrane, refillable reference electrolyte, and built-in temperature sensor.
  • Dedicated for use with Portable Dissolved Oxygen meters.
  • Available also as Multi-Sensor for pH, conductivity and O2 in an all-in-one system.
  • Excellent handling for field testing
  • Clark electrodes are available for SENSION+ DO6 and SENSION+ MM156 portable meters.


Request more information now!
LDO sc sensor for online measurements

Immersion or flow-through probe with optical luminescence measuring method. Years of practical experience have shown that this method completely overcomes the disadvantages of traditional electrochemical O2 measurement methods.
  • Calibration-free & drift-free
  • Extremely reliable - 3 year warranty on probe
  • Remote functions for simple and convenient data transfer via Internet and SMS
  • Can be connected to any SC Controller.


Request more information now!

Special Offers for portable, laboratory and online measurements
Buy a HQD meter with LDO sensor and receive a pH electrode for free!

  • Choose from a portable meter or benchtop meter
  • Choose from a rugged or laboratory LDO sensor
  • Choose from cable length: 1m, 3m, 5m, 10m, 15m, 30m
  • Receive a free pH electrode (PHC20101) and a free pack of SINGLET buffer solutions!

Request a quote now by filling out the form at the top of the page. Please use the drop-down field to select the special offer code.


Buy an LDO sc online sensor and take advantage of the buy one, get one free LDO sc cap offer. Eg, If you buy 4 LDO caps, you will also receive 4 LDO caps for free.


The latest generation of LDO sc online sensors constantly provides information on the current sensor status via PROGNOSYS early warning system.
  • Can be connected to any SC Controller.
  • Extremely reliable: 3 years warranty on probe

Request a quote now by filling out the form at the top of the page. Please use the drop-down field to select the special offer code.

Orders must be placed by June 30th 2014. Offer Code H1419L must be mentioned at time of purchase. Not to be combined with any other discount or offers.