Dissolved Oxygen Meter Advanced Optical probe



Item no. HI-6421-02

More details

1 450 €

HI6421 are streamlined benchtop meters with a large touch screen display, comprised of a housing and an integrated module designed for fresh and saltwater measurements of dissolved oxygen.

Advanced Dissolved Oxygen Meter with Optical DO Probe (opdo®)

HI6421 includes Hanna's HI7641133 optical dissolved oxygen probe (opdo®) that is based on the principle of fluorescence quenching. An immobilized Pt-based luminophore is excited by the light of a blue LED and emits a red light. As oxygen interacts with the luminophore it reduces the intensity and lifetime of the luminescence. The lifetime of the luminescence is measured by a photodetector and is used to calculate the dissolved oxygen concentration.

The probe is fitted with easy to use Smart Caps (HI764113-1) which lock in place and contain pre-loaded calibration coefficients that are automatically transmitted to the probe. The Smart Cap features an immobilized O₂ sensitive luminophore with rugged insoluble black oxygen permeable protective layer.

Over time, the sensor’s optical components can age but are compensated for by using the reference signal to compensate the measuring path. As a result, the sensor provides accurate DO measurements over long periods of time without the need for frequent calibration.


  • Data log collection of up to 1,000,000 data points (with time and date stamp)
  • Logging types: manual, automatic, autohold
  • Sample ID for manual and autohold data

Connectivity Features & Services

  • Transfer logged data to a USB thumb drive
  • Log files that include measurements and calibration data (as .csv file)
  • FTP and email for log export via Ethernet and Wi-Fi connection
  • USB type A for USB stick, keyboard, and printer
  • USB type C for USB stick and PC connection

Smart Cap Technology

Automatic Cap Recognition Hanna's Smart Caps feature a built-in RFID reader that is able to store important data, including manufacture date and first-use date for increased traceabilty.

Longer Life Smart Caps last one year from the date of first use. Your meter will automatically count down from initialization and will have your meter remind you when it has expired with an on-screen message.

Aligned Right Every Time An alignment key ensures that your Smart Cap is on correctly every time.

Specification Detail
DO Range HI6421 - HI7641133 Optical probe: 0.00 to 50.00 mg/L (ppm) concentration; 0.0 to 500.0% saturation.
DO Accuracy (@25˚C) HI6421 - HI7641133 Optical probe: from 0.00 to 20.00 mg/L (ppm) 1.5 % of reading or ± 0.01 mg/L (ppm), whichever is greater
from 20.00 to 50.00 mg/L (ppm) ±5% of reading
from 0.0 to 200.0% saturation ± 1.5% of reading or ± 0.1%, whichever is greater
from 200.0 to 500.0% saturation ±5% of reading
DO Resolution HI6421 - HI7641133 Optical probe: 0.01 mg/L (ppm); 0.1% saturation
DO Calibration DO optical: One or two points automatic calibration at 100% (8.26 mg/L) and 0% (0 mg/L).
Single point manual using a value entered by the user in % saturation or mg/L.
Barometric Pressure Range 450 to 850 mmHg; 600 to 1133 mBar; 60 to 133 kPa; 17 to 33 inHg; 8.7 to 16.4 psi; 0.592 to 1.118 atm
Barometric Pressure Resolution 1 mmHg; 1 mBar; 1 kPa; 1 inHg; 0.1 psi; 0.001 atm
Barometric Pressure Accuracy ±3 mmHg within ±15 % from the calibration point; ±3 mmHg ±1 least significant digit
Temp. Range −20.0 to 120.0 °C
Temp. Resolution 0.1 °C
Temp. Accuracy ±0.2 °C
DO Probe HI7641133 Optical probe
Power Supply DC adapter 100-240AC to 24VDC 2.5A
Environment 0 - 50 °C / maximum 95% RH non-condensing
Dimensions 205 x 160 x 77 mm
Weight Approximately 1.2 kg 
Ordering Information HI6421 is supplied with HI7641133 optical dissolved oxygen probe (opdo®); HI764060 electrode holder; capillary pipette; 24 VDC power adapter; USB-C to USB-A cable; probe quality certificate; quick reference guide with instrument quality certificate.

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