Go Direct® O2 Gas Sensor (GDX-O2)
Specifications and User Guide

NOTE: This is referring to Go Direct® O2 Gas Sensor (GDX-O2) for information about O2 Gas Sensor (O2-BTA) see O2 Gas Sensor Troubleshooting and FAQs.

Primary Test: Blow on the sensor. Do you see a decrease in the Oxygen Gas reading? This tells you that the sensor is responding.

Things to Consider:
1. Has the sensor been stored upright? The O2 Gas Sensor must be stored upright when not being used. This is necessary to maintain the sensor. Failure to store upright will reduce the life of the sensor.

2. Is your data-collection period too short? Diffusion of gases is a fairly slow process; there can be some delay in readings.

3. Are you collecting data in a controlled environment? To collect data in a controlled environment, use the 250 mL Nalgene collection bottle that is included with the sensor.

Please see extended troubleshooting tips in the user manual.


How do I calibrate the Go Direct O2 Gas?
Can my Go Direct O2 Gas Sensor be repaired?
Do any of your sensors require special storage?
Can I use a dishwasher to wash the Nalgene bottle that shipped with my O2 or CO2 Gas Sensor?
How can I insert a CO2 Gas Sensor or O2 Gas Sensor into my own container?
Can O2 gas concentration be expressed in units of mg/m³?
What is the volume of gas displaced by the shaft of the CO2 and O2 Gas Sensor? What is the total volume of the Large and Small BioChambers?


O2 Gas Sensor Specifications

Type: Electrochemical cell
Range: 0-100% (0-1000 ppt) O2
Accuracy: (at standard pressure 760 mm Hg) ±1% volume O2
Typical resolution: 0.01% O2
Response time: ~12 seconds to 90% of final value
Warm-up time: Less than 5 seconds to 90% of final value
Pressure effect: Directly proportional
Pressure range: 0.5 atm to 1.5 atm
Gas sampling mode: Diffusion
Normal operating temperature range: 10 to 40°C
Operating humidity range: 0 to 95% RH

Temperature Sensor Specifications

Type: Thermistor
Range: -25 to 125°C
Accuracy: ±0.5°C
Resolution: 0.1°C
Response time: Less than 5 seconds to 90% of final value
Storage temperature range: -5 to +50°C
Dimensions: Sensor tube: 38 mm length, 28 mm OD; total length: 155 mm
Wireless specification Bluetooth 4.2
USB specification 2.0
Maximum wireless range 30 m
Battery 600 mA
Battery life (single full charge)~24 hours
Battery life (long term)~500 full charge cycles (several years depending on usage)


O2 Gas

The sensor is factory calibrated. For many experiments, it will not be necessary to calibrate. However, for more accurate measurements, the sensor can be calibrated using a one-point calibration using a known concentration of atmospheric oxygen. Enter a value of 20.9% oxygen or a corrected value from the table in the Effect of Humidity section of the user manual for air. Once finished, the sensor should read 20.9% (or the value entered in the table).

O2 Gas – w TC

This channel does not allow calibration since it provides temperature compensated readings. To calibrate the sensor, see the instructions above.


The sensor is factory calibrated and cannot be calibrated by the user.

If the sensor can be turned on when connected by USB but not when disconnected from USB, the battery either needs charging or has reached its end of life and can no longer hold a charge. First, try charging the sensor for several hours. If the sensor still won’t turn on when disconnected from USB, the battery has likely reached its end of life. If you intend to use this sensor wirelessly, the battery will need to be replaced. The rechargeable battery in this sensor is covered by a one year warranty but should last two to five years in typical use.
How do I replace the battery in a Go Direct Wand-Type Sensor?

250 mL Nalgene Bottle w/Lid (CO2-BTL)
BioChamber 250 (BC-250)
BioChamber 2000 (BC-2000)
O2 Gas Sensor to Spirometer Adapter (O2-SPR)