CO2 Gas Sensor (CO2-BTA)

*There are three versions of wired CO2 Gas Sensors. One model was sold up to about January 2007, then replaced with another model from 2007 until May of 2023.  The newest model was introduced in June 2023. Specifications for the different models are listed below.

Troubleshooting

  • Primary Test: Plug in the sensor, start the data-collection program, and allow the sensor to warm up for at least 90 seconds. Blow directly on the shaft of the sensor. You should see an increase in CO2 levels. The pre-2007 model will max out at 5000 ppm. The post-2007 models will max out at approximately 10,000 ppm if set to the Low Range and 100,000 ppm if set to the High Range (although your breath will probably not reach 100,000 ppm).
  • Secondary Test: If the CO2 Gas Sensor is not giving reasonable readings in the Primary Test, try calibrating it. Note: If you recently blew into the sensor for the Primary Test, fan it with fresh air to clear it first.

Additional Troubleshooting

Specifications

  • Response time: 95% of full-scale reading in 120 seconds
  • Warm-up time: 90 seconds
  • Pressure effect: 0.19% of reading/mm of Hg from standard pressure
  • Input potential: 5 V (±0.25V)
  • Gas sampling mode: diffusion
  • Normal operating temperature range: 25°C (±5°C)
  • Operating humidity range: 5–95% (non-condensing)
  • Storage temperature range: –40 to 65°C
  • Measurement Range:
  • ⚬ Low range: 0 to 10,000 ppm CO2
  • ⚬ High range: 0 to 100,000 ppm CO2
  • Typical Accuracy (at standard pressure, 1 atm):
    ⚬ Low range: 0 to 1,000 ppm: ±100 ppm
    ⚬ Low range: 1,000 to 10,000 ppm: ±10% of reading
    ⚬ High range: 0 to 100,000 ppm: ±20% of reading
  • Resolution:
    ⚬ 0 to 10,000 ppm CO2: 3ppm
    ⚬ 0 to 100,000 ppm CO2: 30ppm
Post-2023
  • Measurement ranges
    ⚬ 0-10,000 ppm
    ⚬ 0-100,000 ppm CO2
  • Accuracy
    ⚬ ±100 ppm or ±10% of reading (low range)
    ⚬ ±200 ppm or ±20% of reading (high range)
  • Response time: 95% of full scale reading in 120 seconds
  • Warm up time: 90 seconds
  • Pressure effect: 0.19% of reading/mm Hg from standard pressure
  • Output signal range: 0-4.0 V
  • Input potential: 5 V (±0.25 V)
  • Gas sampling mode: diffusion
  • Normal operating temperature range: 25 ºC (±5 ºC)
  • Operating humidity range: 5–95% (non-condensing)
  • Storage temperature: −40 to 65 ºC
  • Resolution:
    ⚬ 0 to 10,000 ppm CO2: 3ppm
    ⚬ 0 to 100,000 ppm CO2: 30ppm
2007 to 2023
  • Measurement range: 0-5000 ppm CO2
  • Accuracy (at standard pressure, 1 atm)
    ⚬ ±100 ppm in the range of 0–1000 ppm
    ⚬ ±10% of reading in the range of 1000–5000 ppm
  • Typical resolution: 20 ppm
  • Response time: 95% of full-scale reading in 120 seconds
  • Warm-up time (connected to powered interface): 90 seconds
  • Output signal range: 0–2.5 V
  • Output impedance: 1 kΩ
  • Input potential: 5 V (±0.25 V)
  • Gas sampling mode: diffusion
  • Normal operating temperature range: 25 ºC (±5 ºC)
  • Storage temperature range: −40 to 65 ºC
Pre-2007

Calibration

Calibration is usually not necessary, but if needed, it is best to calibrate outdoors in fresh air.

To calibrate, use a paper clip to press and release the “Cal” button on the sensor. The red LED should begin to flash. If you hold it so long that it is a solid red, you have reset the factory calibration. If this happens, simply press and release again. You may have to repeat this two or three times for the CO2 value to adjust to around 400 ppm. Remember that the accuracy is +/- 100 ppm at this range, so it may not read exactly 400 ppm. While calibration is best performed in outside air, which is around 400 ppm in unpolluted air, it can be done in inside air for a quick test of the sensor.  Note: If the button feels like it’s not depressing and the red light does not flash, the button may be stuck under the edge of the plastic. Use the paper clip to free the button and try calibrating again.

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Published: June 20, 2017. Updated: April 21, 2025.