CO2 Readings - Too Low - Smart Gases Pro

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woody_747
Posts: 14
Joined: Wed Feb 07, 2018 3:12 pm
Company: InTechnology WiFi

CO2 Readings - Too Low - Smart Gases Pro

Post by woody_747 » Tue Jul 30, 2019 1:48 pm

Hi,

I am hoping you can help, we are currently in the process of removing 5 smart gases pro sensors that we have installed due to non-viable readings from the CO2 sensors. The expected values for outside fresh air range between 250 and 400 ppm from what I have read but we are seeing ~60ppm from 4 of 5 devices. Could you let me know the first steps I should take to debug this once the units are returned?

Current setup:
A: CO
B: NO2
C: CO2
D: Particle Matter
E: Temp, Hum, Pres
F: O3

Code for the p&s was generated with your online programming cloud service. All P&S devices have the same code apart from the LORA communication settings, yet 4 out of 5 are reading ~60 ppm for CO2 which isn't feasible.

Kind Regards

Kris

libelium-dev
Posts: 27967
Joined: Mon Sep 28, 2009 1:06 pm

Re: CO2 Readings - Too Low - Smart Gases Pro

Post by libelium-dev » Wed Jul 31, 2019 10:23 am

Hi woody_747,

Please test the sensors individually using the example code for the CO2, just attach the sensor in the socket declared in the code and the T/H/P sensor attached to socket E.

http://www.libelium.com/development/was ... s-sensors/

It will be useful if you can enable the debug mode modifying the WaspSensorGas_Pro.h file line 77 from 0 to 2 to get more info. Then share with us the output of the code through the serial monitor.

Regards

woody_747
Posts: 14
Joined: Wed Feb 07, 2018 3:12 pm
Company: InTechnology WiFi

Re: CO2 Readings - Too Low - Smart Gases Pro

Post by woody_747 » Wed Jul 31, 2019 11:26 am

Hi,

The output of the debug code is below,

Faulty reading versus 1 of the probes we have reading correctly. These are INDOOR figures. You can see the first reading is too low and the second is acceptable for indoor reading of CO2. The other 3 faulty probes are all also reading too low on the debug code.

Please advise next steps ASAP. These are in the middle of a pilot so we need these working as soon as possible.

NDIR CO2 example
***************************************
Gas concentration: 480.9463500976 ppm
Temperature: 23.8199996948 Celsius degrees
RH: 61.0458984375 %
Pressure: 98678.3750000000 Pa
J#
NDIR CO2 example
***************************************
Gas concentration: 1034.7388916015 ppm
Temperature: 23.8199996948 Celsius degrees
RH: 60.7080078125 %
Pressure: 98677.4375000000 Pa

Kind Regards

Kris

woody_747
Posts: 14
Joined: Wed Feb 07, 2018 3:12 pm
Company: InTechnology WiFi

Re: CO2 Readings - Too Low - Smart Gases Pro

Post by woody_747 » Wed Jul 31, 2019 1:03 pm

Hi,

Further to the previous post. Please see below issues with a further 4 probes. 2 O3 and 2 NO2. These are values taken with the Electrochemical sample code. The readings are again too low. The ozone readings should never be zero and the NO2 are too low. We tested the NO2 with a generator, reading 0.2 with a "good" probe and 0 from the "faulty" probes. You would at least expect the same reading from different probes due to exactly the same circumstances. I have marked all the good values below as "GOOD READING" the rest of the zero's are the faulty probes.

NO2

J#
Electrochemical gas sensor example
***************************************
Gas concentration: 0.0000000000 ppm
Temperature: 23.8799991607 Celsius degrees
RH: 56.0468750000 %
Pressure: 98773.7343750000 Pa
***************************************
Gas concentration: 0.0000000000 ppm
Temperature: 23.2000007629 Celsius degrees
RH: 61.4160156250 %
Pressure: 98778.6093750000 Pa
***************************************
Gas concentration: 0.0023691389 ppm
Temperature: 21.6000003814 Celsius degrees
RH: 67.7949218750 %
Pressure: 98783.0781250000 Pa
***************************************
Gas concentration: 0.0000000000 ppm
Temperature: 20.6000003814 Celsius degrees
RH: 70.8496093750 %
Pressure: 98788.0390625000 Pa
J#
Electrochemical gas sensor example
***************************************
Gas concentration: 0.0000000000 ppm
Temperature: 20.1700000762 Celsius degrees
RH: 73.5488281250 %
Pressure: 98785.3437500000 Pa
***************************************
Gas concentration: 0.0000000000 ppm
Temperature: 19.9599990844 Celsius degrees
RH: 76.0644531250 %
Pressure: 98783.0546875000 Pa
***************************************
Gas concentration: 0.0000000000 ppm
Temperature: 19.8299999237 Celsius degrees
RH: 76.5429687500 %
Pressure: 98792.1718750000 Pa
J#
Electrochemical gas sensor example
***************************************
Gas concentration: 0.2091375112 ppm - GOOD READING
Temperature: 19.7800006866 Celsius degrees
RH: 76.6601562500 %
Pressure: 98791.3593750000 Pa
***************************************
Gas concentration: 0.2069130420 ppm - GOOD READING
Temperature: 19.7099990844 Celsius degrees
RH: 77.6347656250 %
Pressure: 98796.8125000000 Pa
J#
Electrochemical gas sensor example
***************************************
Gas concentration: 0.0000000000 ppm
Temperature: 19.7299995422 Celsius degrees
RH: 77.6484375000 %
Pressure: 98801.1875000000 Pa

Ozone

Electrochemical gas sensor example
***************************************
Gas concentration: 0.1558337783 ppm . - GOOD READING
Temperature: 19.3899993896 Celsius degrees
RH: 79.2285156250 %
Pressure: 98794.7031250000 Pa
J#
Electrochemical gas sensor example
***************************************
Gas concentration: 0.0000000000 ppm
Temperature: 19.2999992370 Celsius degrees
RH: 80.0888671875 %
Pressure: 98797.5000000000 Pa
***************************************
Gas concentration: 0.0000000000 ppm
Temperature: 19.2700004577 Celsius degrees
RH: 79.5742187500 %
Pressure: 98805.5000000000 Pa
J#
Electrochemical gas sensor example
***************************************
Gas concentration: 0.0000000000 ppm
Temperature: 19.2800006866 Celsius degrees
RH: 79.3066406250 %
Pressure: 98803.7343750000 Pa
***************************************
Gas concentration: 0.0000000000 ppm
Temperature: 19.2199993133 Celsius degrees
RH: 79.7011718750 %
Pressure: 98812.6562500000 Pa

Kind Regards

Kris

libelium-dev
Posts: 27967
Joined: Mon Sep 28, 2009 1:06 pm

Re: CO2 Readings - Too Low - Smart Gases Pro

Post by libelium-dev » Wed Jul 31, 2019 2:19 pm

Hi,

We have contacted you through mail to solve the issue with CO2 sensors.

Regarding O3 and NO2 sensors you are getting normal values, notice the concentration of the gases in a not polluted area is very low, the difference between sensors could be caused by the accuracy of the sensor, +-0.2 in O3 and +-0.1 in NO2.

Also, notice the node should be working for a while (some loops) until the sensor output is stabilized.

Regards

woody_747
Posts: 14
Joined: Wed Feb 07, 2018 3:12 pm
Company: InTechnology WiFi

Re: CO2 Readings - Too Low - Smart Environment Pro

Post by woody_747 » Wed Jul 31, 2019 3:02 pm

Hi,

Thanks for coming back to me.

In the case of the tolerances then, are these sensors suitable for reading the NO2 pollution from a busy road? Some of the material I have read are in PPB not PPM which would make me concerned about the sensitivity.

We have the Smart Environment Pro board, is this also the correct board?

Kind Regards

Kris

libelium-dev
Posts: 27967
Joined: Mon Sep 28, 2009 1:06 pm

Re: CO2 Readings - Too Low - Smart Gases Pro

Post by libelium-dev » Thu Aug 01, 2019 7:27 am

Hi,

The sensitivity of these sensors is measured in ppm and not ppb. You can consult the accuracy of each sensor in the Gases sensor boar PRO guide. Yes you're using the correct board.

Using NO2 sensor in a busy board will report values if there is enough concentration of the gas.

Regards.

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