Calibration
You should not have to perform a new calibration very often when using the
CO
2
Gas Sensor. A calibration is stored on the sensor before it is shipped. If you
do find that you need to calibrate your CO
2
Gas Sensor, it can be done using one
known CO
2
level. The calibration will be based on a sample of outside air having
a carbon dioxide concentration of about 400 ppm. Levels in your area may be
slightly higher due to localized influences such as automobile or industrial
emissions of carbon dioxide.
Note:
This calibration method is different from the
usual two-point calibration performed with other Vernier sensors. To calibrate the
CO
2
Gas Sensor:
1. Fill the gas sampling bottle (included with the sensor) to the brim with water,
take it outside, and dump the water to ensure it is filled with fresh air. While
still outdoors, insert the sensor into the gas sampling bottle containing fresh
outside air. You can now take the bottle and sensor to the location where the
calibration is to be done.
2. Connect the CO
2
Gas Sensor to the data-collection interface. Start the
data-collection software and identify your interface, if necessary. Let the sensor
warm up for at least 90 seconds.
3. When the CO
2
Gas Sensor has warmed up (readings should have stabilized),
use a paper clip to press down the calibration button. Release the button as
soon as the red light starts to blink. After about 30 seconds, the reading should
stabilize at a value of approximately 400 ppm (±100 ppm). If the reading is
significantly lower or higher than 400 ppm, simply press the button again to
repeat the process.
Note:
If the red light stays on solid, you have held the
button too long. In this case, wait for it to go off and press it again, releasing
as soon as it begins to flash.
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Specifications
Measurement range of CO
2
Gas Sensor Low range: 0 to 10,000 ppm CO
2
High range: 0 to 100,000 ppm CO
2
Low range typical accuracy
(at standard pressure, 1 atm)
0 to 1,000 ppm ±100 ppm
1,000 to 10,000 ppm ±10% of reading
High range typical accuracy
0 to 1,000 ppm ±100 ppm
1,000 to 100,000 ppm ±20% of reading
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
Output signal range
0 to 4.0 V
Input potential
5 V (±0.25 V)
Gas sampling mode
diffusion
Normal operating temperature range
25°C (±5°C)
Operating humidity range
5 to 95% (non-condensing)
Storage temperature range
–40 to 65°C
13-bit resolution
0 to 10,000 ppm CO
2
: 1.5 ppm
0 to 100,000 ppm CO
2
: 15 ppm
12-bit resolution
0 to 10,000 ppm CO
2
: 3 ppm
0 to 100,000 ppm CO
2
: 30 ppm
10-bit resolution
0 to 10,000 ppm CO
2
: 12 ppm
0 to 100,000 ppm CO
2
: 120 ppm
Care and Maintenance
Very important:
Do not allow any liquids to come in contact with the CO
2
Gas
Sensor. The sensor is intended only for measuring gaseous, not aqueous, CO
2
concentration.
Temperatures greater than 65°C will damage the sensor.
It is recommended that you wash the gas sampling bottles by hand. Most
dishwashers will melt the plastic.
How the Sensor Works
The Vernier CO
2
Gas Sensor measures gaseous carbon dioxide levels in the range
of 0 to 10,000 ppm (Low range setting) or 0 to 100,000 ppm (High range setting)
by monitoring the amount of infrared radiation absorbed by carbon dioxide
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