The SO-120 has a standard response time of 60 seconds and is designed for use in soil applications. It comes with a thermocouple wire to correct for temperature changes and a restive heater to raise the temperature of the membrane approximately two degrees above ambient temperature to keep condensation from occurring on the Teflon membrane and blocking the diffusion path of the sensor. 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 sailings, monitoring redox potential in soils, and determination of respiration rates through measurement of O2 consumption in sealed chambers or measurement of O2 gradients in soil/porous media.
Measurement Range 0 to 100 % O₂
Sensitivity (at sea level, 101.3 kPa) 52-58 mV in 21 % O₂, 2.6 mV per % O₂, 26 µV per 0.01 % O₂
Response Time (time required to read 90 % of saturated response) 60 seconds
Output at 0 % O2 5 % of output at 20.95 % O₂ or 2.5 ± 1 mV
Measurement Repeatability Less than 0.1 % of mV output at 20.95 % O₂
Non-linearity Less than 1 %S
ignal Decrease per Year 1.8 % per year (1 mV per year)
Oxygen Consumption Rate 2.2 µmol O₂ per day at 20.95 % O₂ and 23 C
Operating Environment -20 to 60 C, 0 to 100 % relative humidity (non-condensing), 60 to 140 kPa
Input Voltage Requirement 12 V DC continuous (for heater), 2.5 V DC excitation (for thermistor)
Heater Current Drain 6.2 mA (74 mW power requirement when powered with 12 V DC source)
Thermistor Current Drain 0.1 mA DC at 70 C (maximum, assuming input excitation of 2.5 V DC)
Dimensions 32 mm diameter, 68 mm length
Mass 175 g (with 5 m of lead wire)
Cable 5 m of six conductor, shielded, twisted-pair wire
Warranty 4 years against defects in materials and workmanship
