CO₂ Gas Sensor (CO2-BTA)
Specifications and User Guide

Troubleshooting

Note: There are two types of CO₂ Gas Sensors. One model was sold up to about January 2007. The new model was sold after January 2007 and replaces the old model. Specifications for both models are in this article.

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 older model will max out at 5000 ppm. The newer model will max out at 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, wave it around to clear it first.

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, which is not what you want to do. 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 will not read exactly 400 ppm. Ideally, this is done in outside air, which is around 400 ppm in unpolluted air, but for a quick test of the sensor, it can be done in inside air. Just don’t forget to re-calibrate it in outside air before getting the most accurate values. 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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Specifications

New order code: CO2-BTA (2007 to present)
Former order code: CO2-DIN/CO2-BTA (prior to 2007)

Measurement range: 0-5000 ppm CO₂ (old model); 1-10,000 ppm and 0-100,000 ppm (new model)

Former Model Specs

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, old model: 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 deg C (+/- 5 deg C)
Storage temperature range: −40 to 65 deg C

New Model Specs

Accuracy
+/- 100 ppm or +/- 10% of reading (low range)
+/- 200 ppm or +/- 20% of reading (high range)
Typical resolution:
13-bit resolution (SensorDAQ): 1.5 ppm (low range); 15 ppm (high range)
12-bit resolution (LabPro, LabQuest, Go! Link, ULI, or SBI): 3 ppm (low range); 30 ppm (high range)
10-bit resolution (CBL 2): 12 ppm (low range); 120 ppm (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 deg C (+/- 5 deg C)
Operating humidity range: 5–95% (non-condensing)
Storage temperature: −40 to 65 deg C

Calibration

Calibrate? Usually no.
If you do find that you need to calibrate your CO₂ Gas Sensor, it can be calibrated using one known CO₂ level. Note: This calibration method is different from the usual two-point calibration performed using other Vernier sensors. See the CO₂ Gas Sensor Specifications and User Guide for detailed instructions on how to calibrate.

If you wish to reset the CO₂ Gas Sensor to its factory default calibration values (new model only), press and hold the Calibration button for approximately 5 seconds. The red light will change from flashing to steady. When the light turns off, the sensor will be back to its factory settings for that range. This procedure is not the preferred method of calibration due to the fact that the sensor response may have drifted over time. A custom calibration as described above is preferred.

Sensor ‘CO2 Gas’ (pre-2007)
Calibration ‘CO2 ppm’:
Equation: Linear
y = bx + a
a: 0
b: 2000
Calibration ‘CO2 ppt’:
Equation: Linear
y = bx + a
a: 0
b: 2
Calibration ‘CO2 %’:
Equation: Linear
y = bx + a
a: 0
b: 0.2
Calibration ‘CO2 mg/m^3’:
Equation: Linear
y = bx + a
a: 0
b: 3551.6

Low Range

Sensor ‘CO2 Gas Sensor'(post-2007)
Calibration ‘CO2 Low ppm’:
Equation: Linear
y = bx + a
a: 20
b: 2500
Calibration ‘CO2 Low ppt’:
Equation: Linear
y = bx + a
a: 0.02
b: 2.5
Calibration ‘CO2 Low %’:
Equation: Linear
y = bx + a
a: 0.002
b: 0.25
Calibration ‘CO2 Low mg/m^3’:
Equation: Linear
y = bx + a
a: 35.516
b: 4439.5

High Range

Calibration ‘CO2 High ppm’:
Equation: Linear
y = bx + a
a: 20
b: 25000
Calibration ‘CO2 High ppt’:
Equation: Linear
y = bx + a
a: 0.02
b: 25
Calibration ‘CO2 High %’:
Equation: Linear
y = bx + a
a: 0.002
b: 2.5
Calibration ‘CO2 High mg/m^3’:
Equation: Linear
y = bx + a
a: 35.516
b: 44395

Related Vernier Products

250 mL Nalgene Bottle w/Lid (CO2-BTL)
BioChamber 250 (BC-250)
BioChamber 2000 (BC-2000)