Use the pictures below to determine which version of the O₂ Gas Sensor (O2-BTA) you have.

• Sensors sold from June of 2021 are black with a rounded top. The label is bright green with white lettering. The calibration button is recessed and is located on the side of the sensor.
• Sensors sold from May 2007 to May of 2021 have a round top, and are black with a black label with white lettering. Two green o-rings frame the label. The calibration button is recessed and is located on the side of the sensor.
• Sensors sold before April 2007 have a calibration button on the top of the sensor. The top of the sensor is also flat. The label is light green with black lettering. The caliper logo is prominent and is located above the lettering for Vernier. Four small holes are also located around the port / opening of the sensor at its base.

The oldest version of Oxygen Gas Sensor does not have a sensing element that can be replaced. The current version of the Oxygen Gas Sensor and versions sold between May 2007 to May of 2021 have a sensing element (cell) that can be replaced. Please see Can my O2 Gas Sensor (O2-BTA) be repaired?.

Please note that there is also the Go Direct^® O₂ Gas Sensor (GDX-O2).

If you need to measure dissolved oxygen, consider the Vernier Optical DO Probe (ODO-BTA) or the Go Direct^® Optical Dissolved Oxygen Probe (GDX-ODO)

The sensor manual for the Oxygen Gas Sensor sold from 2007-2021 can be found below.