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Enabling better global research outcomes in soil, plant & environmental monitoring.

Apogee MO-200: Portable Oxygen Sensor with Handheld Meter

The MO-200 is designed to measure 5 – 100% oxygen while the handheld meter displays and stores measurements. The wide measurement range allows it to be used for applications either in the soil or in the lab with the available diffusion or flow-through heads. The sensor is calibrated to ambient air making it very easy to calibrate. An aluminium housing that is filled with epoxy allows the sensor to withstand harsh conditions.

  • Designed to measure 0 – 100% Oxygen in soil, growth media, air, or in-line tubing (flow-through applications)
  • Includes temperature sensor to compensate for temperature changes
  • Integrated heater prevents condensation for use in conditions where relative humidity can reach 100%
  • Available in sensor-only version with pigtail leads (for dataloggers) or with handheld meter

All Apogee oxygen meters can be purchased with attachments to facilitate measurements in soil/porous media or inline tubing.

Model AO-001:
Diffusion head designed for measurements in soil/porous media. The diffusion head maintains an air pocket and provides protection to the permeable Teflon membrane where gas diffusion occurs.

Model AO-002:
Flow through head designed for inline measurements. The flow through head allows connection of tubing via ¼ inch barbed nylon connectors.

In applications with high humidity, condensation can occur on the Teflon membrane, blocking the diffusion path of the sensor. To prevent this, a resistive heater is included to raise the temperature of the membrane approximately two degrees above ambient temperature.
*Measurement of oxygen below 1% requires special calibration. Contact Technical Support for more details.

Apogee Instruments MO-200 oxygen meters consists of a handheld meter and a dedicated oxygen sensor connected by cable. The separate sensor consists of a galvanic cell sensing element (electrochemical cell), Teflon membrane, and signal processing circuitry mounted in a stainless steel housing (or ABS plastic housing for use in acidic environments). The MO-200 oxygen meter includes manual or automatic data logging features for making spot-check measurements or monitoring oxygen concentration over time.

The sensors on Apogee MO-200 oxygen meters are built with an anodised aluminium housing (or ABS plastic housing for use in acidic environments) and are designed to be installed in soil/porous media or sealed chambers, in addition to air. To facilitate the most stable readings, sensors should be mounted vertically, with the opening pointed down and the cable pointed up. This orientation allows better contact between the electrolyte and signal processing circuitry.

Apogee oxygen sensors can be used in conjunction with carbon dioxide sensors to help improve the characterisation of soil respiration. Typically, soil oxygen sensors use a galvanic cell to produce a current flow that is proportional to the oxygen concentration being measured. These oxygen sensors are buried at various depths to monitor oxygen depletion over time, which is then used to predict soil respiration rates. Apogee oxygen sensors are equipped with a built-in heater to prevent condensation from forming on the permeable membrane, as relative humidity can reach 100 percent in soil.

Measurement Range 0 to 100 % O₂
Measurement Repeatability ± 0.1 % at 20.9 % O₂ Non-linearity Less than 1 %
Oxygen Consumption Rate 2.2 µmol O₂ per day at 20.9 % O₂ and 23 C
Response Time 14 s (time required to read 90 % of saturated response)
Operating Environment 0 to 50 C, less than 90 % non-condensing relative humidity up to 30 C, less than 70 % non-condensing relative humidity from 30 to 50 C, 60 to 140 kPa Meter
Dimensions 12.6 cm length, 7.0 cm width, 2.4 cm height Sensor
Dimensions 3.2 cm diameter, 6.8 cm length
Mass 210 g
Cable 2 m of two conductor, shielded, twisted-pair wire with santoprene rubber jacket (high water resistance, high UV stability, flexibility in cold conditions), additional cable available
Warranty 4 years against defects in materials and workmanship


The MO-200 is designed to measure 0 to 100 % oxygen and is connected to a hand-held meter via cable that displays and stores measurements. The wide measurement range allows it to be used for applications either in the soil or in the lab with the diffusion or flow-through head accessories. The sensor is housed in a polypropylene body and electronics are fully potted. Typical applications include measurement of O2 in laboratory experiments, monitoring gaseous O2, in indoor environments for climate control, monitoring of O2 levels in compost piles and mine tailings, monitoring redox potential in soils, and determination of respiration rates through measurement of O2 consumption in sealed chambers, or measurement of O2 gradient in soil/porous media.

The meter has a sample and log mode, and will record an average daily value. Sample mode will record up to 99 manual measurements. Log mode will power the meter on/off to make a measurement every 30 seconds. Every 30 minutes the meter will average the sixty 30 second measurements and record the averaged value to memory. The meter can store up to 99 averages, once full it will start to overwrite the oldest measurement with new ones. An average daily value will be recorded from the 48 averaged measurements (making a 24 hr period). Sample and log measurements can be reviewed on the LCD display or by downloading the data to a computer, however, the average daily value can only be viewed by downloading the data to a computer. Downloading data to a computer requires the AC-100 communication cable (a standard USB cable will not work) and ApogeeAMS software.