Can be used to make measurements of the level of free-oxygen in air or dissolved oxygen in water. The free-oxygen in air mode is used to measure changes in oxygen levels during combustion. The dissolved oxygen mode is useful in the study of photosynthesis. The oxygen sensor is designed for use both in the laboratory and in the field. All Edu-Logger Sensors must be used in conjunction with the USB Module (X162672) or the Wi-Fi Module (X162773).