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CO₂ sensor

User22572
New Contributor

Dear CO2 team,

 

During the testing of the CO2 sensor I noticed an increased noise figure of the sensor.

Below approximately 620 ppm the noise figure increases. I have no idea why.

All sensors are placed in an temperature controlled chamber.

211110_PASCO2_1.png

In the picture you can see 4 lines:

 

Red = PASCO2 sensor A, interfaced via I2C with our own electronics (interval 5 [s])

Blue = PASCO2 sensor B, interfaced via USB with the evaluation board (interval 10 [s] ?)

Green = SCD41 sensor (Sensirion), interfaced via I2C (interval 5 [s])

Cyan = 415 [ppm] (outside air)

 

In the bottom graph you can see the difference between successive measurements which we use as a noise figure.

Why is this sensor displaying this behaviour? and how can I resolve this issue?

 

Kind regards,

Martin

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5 Replies
adib
Employee

Hallo sir, can you please share some more details on your setting. For reading out, which mode are you using? Single shot mode or continuous mode of operation?

Best regards,
XENSIV PAS CO2 support team

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User22572
New Contributor

Dear Adib,

 

We are using the continuous mode with a measurement rate of 5 seconds.

This behaviour disappears with a measurement rate of 10 seconds or more.

211112_PAS_CO2_CO2_vs_measurement_rate.png

Kind regards,

Martin

 

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mht
Employee

Hi Martin,

One of the sensor documents states the sampling rate should be greater than or at least 10s to insure the IR emitter is "cooled down" completely. Otherwise I would assume the measurement includes some "residue" from the previous one. Your charts are showing nice readings when the sampling (measurement) rate is >= 10s. 

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User22572
New Contributor

Hello mht,

 

Personally I think this should me made more clearly in the datasheet.

Why would this be an issue below 620 ppm and not above?

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adib
Employee

Dear Martin,

This topic has been addressed as a Bug. We are on this topic and will give you a reply as soon as we have an update.

Best regards

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