Benchtop Dissolved Oxygen Meter

What is the Benchtop Dissolved Oxygen Meter?

A benchtop dissolved oxygen meter is a mains-powered instrument for laboratory measurement of oxygen in water and culture media, with temperature, salinity and pressure corrections built in. It is used for BOD determinations, fermentation development, validation rinses and research where documented accuracy matters.

Overview

The benchtop meter combines a polarographic or optical probe with a stirrer and a temperature sensor to give stable readings in beakers and BOD bottles. Typical ranges are 0 to 20 mg/L with resolution of 0.01 mg/L and accuracy of plus or minus 0.1 to 0.2 mg/L, and percent saturation is displayed alongside concentration. Built-in salinity and barometric pressure corrections, plus automatic temperature compensation, allow readings in brackish water and at altitude to be reported correctly. GLP functions record calibration data, probe type, operator and sample identification, and results are exported to a computer or LIMS. Many units also measure pH, conductivity or ORP with additional probes, so one instrument covers common water testing. Accessories include a self-stirring BOD probe, membrane kits, electrolyte and a calibration chamber for water-saturated air.

How does it work?

Electrochemical sensors are either galvanic or polarographic. Oxygen diffuses through a gas-permeable membrane into an electrolyte, where it is reduced at a cathode; the resulting current is proportional to the oxygen partial pressure. Polarographic cells need an applied voltage of about 0.7 V and a warm-up period, while galvanic cells generate their own current. Optical sensors use a luminescent dye immobilized in a film: blue light excites the dye, the emitted red light is quenched by oxygen, and the phase shift of the signal gives the oxygen concentration. Optical sensors need no electrolyte, flow, or polishing and hold calibration for months. Both types measure partial pressure, so salinity and barometric pressure corrections are applied to report concentration in mg/L, and a temperature sensor compensates the membrane permeability or dye response. Stirring or flow across the membrane is required for electrochemical sensors to avoid oxygen depletion at the surface.

What are the key features?

• Measuring range 0 to 20 mg/L with 0.01 mg/L resolution
• Automatic temperature, salinity and barometric pressure correction
• Self-stirring BOD probe for five-day depletion measurement
• GLP memory for calibration, probe type and sample identification
• Optional pH, conductivity or ORP channels on one instrument
• USB or RS-232 output to computer or LIMS

What are the technical specifications?

A typical benchtop dissolved oxygen meter configuration offers measuring range of 0–20 mg/L (0–200% saturation), resolution of 0.01 mg/L, 0.1% saturation, accuracy of ±0.1–0.2 mg/L, response time of ≤30 s to 90%, temperature range of 0–50 °C and temperature compensation of Automatic, 0–50 °C. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Benchtop Dissolved Oxygen Meter is used in BOD5 determination in wastewater, fermentation and cell culture development, water and wastewater laboratory QC, aquaculture research and drinking water validation rinses. Across the wider Dissolved Oxygen Meters class, laboratories also deploy it for municipal wastewater aeration control, fermentation and bioprocess monitoring and aquaculture pond and tank control.

Which standards and certifications apply?

Relevant standards and methods include ISO 5814, ASTM D888, APHA 4500-O Standard Methods, EN 25814, GB/T 11913 and USP <1231>. Certification candidates for this model are CE, RoHS and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Calibrate electrochemical sensors in water-saturated air or against a reference method such as Winkler titration, and replace the membrane, electrolyte and O-ring at the interval the manufacturer specifies, commonly every one to three months. Keep the membrane free of deposits: biological growth in wastewater reduces response and must be cleaned without scratching the surface. Optical sensors need only periodic recalibration, but the sensing cap has a finite life of roughly one to two years and must be replaced. Zero-point checks with sodium sulfite solution confirm that the instrument reads low oxygen correctly. Record temperature, salinity and barometric pressure corrections with the data, and verify performance with a check standard or comparison measurement. For compliance work, follow the method required by the permit or pharmacopoeia and retain calibration and maintenance records.

How do I select the right Benchtop Dissolved Oxygen Meter?

Choose a benchtop meter for laboratory dissolved oxygen work with documented accuracy, including BOD5 and fermentation studies. It is not suitable for continuous process control. In an RFQ, specify range, resolution, probe technology, whether a self-stirring BOD probe is included, correction features, data output and any additional parameters required.

How does it compare with other Dissolved Oxygen Meters variants?

Choose between electrochemical and optical sensing first. Optical sensors suit long-term unattended monitoring and low-maintenance field work, while electrochemical sensors have lower initial cost and are well established in wastewater aeration control. Then match the format: benchtop meters for laboratory BOD, fermentation and validation work, portable meters with long cables for rivers, lakes and tanks, online analyzers with 4-20 mA outputs for aeration control, and BOD systems that measure depletion over five days. Check the measuring range, accuracy, temperature and salinity compensation, response time, minimum flow or stirring requirement, calibration method and logging capacity. Specify whether readings must be in mg/L, percent saturation or both, and which standards the laboratory follows.