Theory of Operation

The ethylene sensors in the F-900 are electrochemical. With this type of sensor, the gas sample travels across the surface of the electrode and diffuses into the electrochemical where ethylene is oxidized. The current created by the oxidation is measured and converted to parts per million (ppm) of ethylene.

Figure 6: Diagram of an electrochemical sensor. (A) working electrode (R) reference electrode (C) counter electrode (E) electrolyte. Image credit: doi:10.1093/aob/mcs259.

The F-900 flow rate is regulated by a pump and a flow meter. Additional optional sensors are enabled/disabled in the Setup Menu (see page 2), as well as “conditioning chambers” on the back of the instrument (see page 2).

The temperature and relative humidity sensors are located inside the instrument. Therefore, the temperature sensor is subject to heating by the F-900 internal electronics. The temperature reading is often 4-5°C above ambient and in turn, relative humidity readings are affected. The use of water in Chamber In (PolarCept, see page 8), will also affect relative humidity readings.

Figure 7: Flow path diagram of the F-900 ethylene analyzer. Dashed line indicates optional flow path capabilities.