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Dear Sir,

I have following two sensors.

1) NAP-21A CO2 Sensor
Data Sheet >> http://www.eleparts.co.kr/front/download.php?file_name=NAP-21A.pdf
Image >> http://www.ebay.com/itm/1pcs-Gas-Sensor-NAP-21A-/321033768853?pt=LH_DefaultDomain_0&hash=item4abf1a8f95

2) MG811 CO2 Sensor
Data Sheet >> http://www.parallax.com/Portals/0/Downloads/docs/prod/sens/MG811Datasheet.pdf
image >> http://www.ebay.com/itm/MG811-CO2-Dioxide-Sensor-Module-/370650102200?pt=US_Amplifier_Parts_Components&hash=item564c77b9b8

According to the data sheets
NAP-21A sensor can detect CO2 0% to 100%
MG811 sensor can detect CO2 350ppm to 10000ppm

Actually I want to detect CO2 up to (0% - 15%)V/V. Then what is the suitable sensor for my purpose ? Which sensor has good detection range according to the data sheets ?

Thanks
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ppm - part per million, it looks like second sensor could measure up to 10 000/1000 000 = 1%, well below your expected 15%
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Hi I have bought few sensors form
H-Instruments, and they have all worked well, http://h-instruments.ecrater.com/c/135013040/arduino-wireless
John
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ppm - part per million, it looks like second sensor could measure up to 10 000/1000 000 = 1%, well below your expected 15%

Hello Magician,

Did you read 2 data sheets ? What do you think about two sensors ? Which one has good detection range ?

Waiting for your reply.

Thanks.
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Quote
Did you read 2 data sheets ?
No, just one .
What do you think about two sensors ?
N/A.
Which one has good detection range ?
"GOOD" is not technical term.
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Quote
Did you read 2 data sheets ?
No, just one .
What do you think about two sensors ?
N/A.
Which one has good detection range ?
"GOOD" is not technical term.

Hello Magician,

Which one has large detection range ?

NAP - 21A >> Linear output signals to CO2 gas concentration of 0 to 100%
MG811 >> 350—10000ppm CO2

plz tell me which sensor can detect large concentration of CO2 ?

Thanks
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Hope, you are not under drugs, probably "evil's force Z" distort may response:
Quote
ppm - part per million, it looks like second sensor could measure up to 10 000/1000 000 = 1%, well below your expected 15%
If you are asking what has lager range 1% or 100%? It's obvious, isn't it?
BTW, link to datasheet of first sensor navigate to ebay where there is no datasheet.
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BTW, link to datasheet of first sensor navigate to ebay where there is no datasheet.

This is the data sheet.

1) NAP-21A CO2 Sensor

Data Sheet >> http://www.eleparts.co.kr/front/download.php?file_name=NAP-21A.pdf
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Im going to assume the first sensor is more accurate within its smaller range and the second one just has a larger range for reading extremely high Co2 but less accuracy.

So it depends what you need it for.
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I have myself a MG-811 sensor with a sandbox electronics board for signal conditioning (http://sandboxelectronics.com/store/index.php?main_page=product_info&cPath=66&products_id=197) and I have mixed feelings about it.

- It is not too expensive ($54, I think) considering that CO2 gas sensors are not the cheapest gas sensors.
- It needs heating, so there is a DC input on the board. This heating circuit makes the sensor use too much power for batteries.
- Heating time. I am experiencing long heating times until readings are stable. Normally, as soon as you turn it on, measures are very high. Slowly they go down to the real level. But for me, this is taking up to 10 minutes. I don't know if it is a problem with my unit or it is the usual behaviour.
- Calibration. On the specs, you can read that every unit must be calibrated. You must calculate 2 voltages. One is for fresh air, which is ok, you can run the sensor for a period of time at your window and look for the voltage corresponding to smallest ppm concentration . BUT you need a second calibration point with 1000 ppm gas. This gas is quite expensive (a kit for 20 calibration costs $600).

So, by the moment I am running the device without knowing how accurate measures are.

I am seriously considering buyin a ndir CO2 sensor, which only needs fresh air calibration. Probably Cozir ambient.

Hope this helps

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@jcasmen: what are you measuring CO2 for? I have paid for the same sensor, but not received it yet... :-(

Interesting to read your experience. The fresh air calibration sounds fine. CO2 calibration not so much, I should have read the datasheet before purchase. Silly, silly.

For my purposes, a relative reading is probably going to be sufficient, however. If I get a baseline reading, over time I can track changes vs that baseline and that should be sufficient.

Can you leave these things running, assuming you have the power? Or do they er burn out after a while? Another datasheet read for MTBF, I guess?
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