Multiple BME680 Sensor Mounted On Same Location & While Comparing there is offset in the values?

[msalmankhan]

Hello Everyone , I am conducting some tests on the BME680 sensors  and their respose to the enviroment, So  for the test purpose I have placed two of the sensor exactly on the same location , and others are placed at some distance from them, I have let the sensors to run for 3 days,after three days , I have burnt some plastic material, in order to create smoky enviroment, the enviromentwas quite smoky, 
What I found some strange things , the two sensors placed next to each other  performs differently , Which I will  show  you on the graph , The two sensors placed almostly on the same location , then it should responeded to the enviroment in exactly the same way, but from the graph it behaves differently I just want to know the reason why this different behaviour is shown by the sensor that are placed exactly on the same location.

Note: I am using BSEC Library , and the sensors are operating in LP Mode, IAQ Configuration is : generic_33v_300s_4d, but because I am using LP mode of the sensor , the interval between readings is : 3 Seconds.

Two sensor placed next to each other , marked with white Color pencile, The shape of the graph are different

As you can see the sensor marked with white colour , are placed next to each other , but the graph shows different behaviour, This should be of same shape.

NOTE: This is the Static IAQ values reporting by the sensors.

Any help in regarding this will much be appreciated Thanks.

[BSTRobin]

Hi msalmankhan,

Need you confirm are they the IAQ output curves of sensors 1 and 2 respectively in the picture?

What are the accuracy values of the two sensors?

[msalmankhan]

Yes Static IAQ Curves of sensor 1 and sensor 2  in the respective images . They are started at the same time  and placed next to each other as you can varify from the timing  in the x-axis , Initially the IAQ Accuracy was 3 , and then changed to 2 and then goes back to 3 for both sensors during this "Time Slice".

[NickXML]

Just to add to this discussion: we are running four sensors in two pairs. Each pair has a sensor labeled 008 and one labeled 009. All sensors are running in LP mode, but one pair sends data every 20s, the other pair sends data every 60s.

However, both 008 sensors (one from each pair) are close to each other. Both 009 sensors are literally next to each other.

We are currently running an experiment where every 2 hours some VOCs are introduced into the area, hence the regular spike in IAQ values.

The attached graphs show some pretty big differences between the sensors that are in the same location. Please compare the 008 data from the graph labeled "cont" to to the 008 data on the graph labeled "1 min", and the similar graphs for the two 009 sensors.

[NickXML]

The IAQ Accuracy for the pair reporting every 20s is mostly 3 with occasional dips to 2.

The IAQ Accuracy for the pair reporting every minute is a solid 3.