BME688 Calibration Details

[sanath101]

Hello Team,

We are working on a requirement for detecting the CO2 gas and VOC  percentage in the room.

Also in addition we need ambient temperarture ,Humidity and Pressure of the room.

Below are my queries.

1. Does CO2 and VOC detection needs for training of BME688?Or by using the default configuration will it be able to detect these?

2. My understanding from the datsheet is in Parallel mode the Temeprarture ,Humidity and Pressure will be read in parallel when Heating profile starts, does this heating profile Impact on temperarture,humidity and pressure?

3.To teach the BME688 for detection of different gases ,does Bosch India has lab set up where we can approach or do you have any other reccomendation to test?Can we approach any other vendor ?

4.Any Calibrartion is required  for Tempearature,Humidity,Pressure and others?

Regards,

Sanath

[sanath101 · Accepted solution]

Hi Team,

Can anyone please guide us through this.Its an urgent requirement.

Regards

Sanath

[kmca · Accepted solution]

CO2 is a calculated/estimated value based on an algorithm designed by Bosch Sensortec.  Whilst there is no training required, the sensors need to be burned in and you will need to understand saving and loading state in order to shorten the time required for the sensor to achive stability (quality 3). 

The BME688 is a MOX sensor, with the ability to change the heater profile in order to better characterise  VOC (volatile organic compounds) being sampled. The IAQ (Indoor Air Quality) is derived from resistance readings using an algorithm designed by Bosch Sensortec.

If you wish to identify a specific compound - aka sniff - then you have to train on what it is you are trying to detect.  You really need a Bosch Sensortec Dev Kit  (8 sensors) to sample enough data for sucessful learning, and data on up to 4 seperate compounds can be used in a single model  . A single sensor can be used to deploy the generated module, in scanning mode sniffing for  a match. 

When you download the BESC2.X library from Bosch Sensortec  there is an Integration Guide which I suggest you read carefully. 

Bosch Sensortec say that the BME 688 compensates for the heater impact, but there are often other sources of heat, so in my experience this is an issue and you may need to calibrate, depending on your requirement/design. 

Regards

Keith

[BSTRobin · Accepted solution]

Hi sanath101,

Please refer to the following reply:
1. BSEC algorithm already provides CO2 equivalent estimate [ppm] and Breath VOC concentration estimate [ppm] outputs by default and does not require training. You can check if this is the output you need?
2. BSEC algorithm compensates for temperature, humidity, and pressure sensor, and when using a heater profile for heating, it does not affect temperature, humidity, or pressure;
3. We currently do not have gas lab or recommended third parties;
4. If you use the sensor API of BME68x and BSEC algorithm, there is no need for additional calibration for temperature, humidity, and pressure sensor.