BME280 Humidity Noise

[aparr001]

We have been testing out the BME280 in our design and have noticed the humidity reading has a large periodic noise.  Temperature and Pressure do not.  I don't believe it is our design as we have tried running the BME280 off a low noise 3.0V LDO for VDD and the 3.3V for VDDIO.  We have also filtered it quite heavily with ferrite beads and small series resistance.  I've also hacked in an Adafruit PCB and it still has the same noise.  Our software engineer works remote and his unit does the same thing as well.  I've attached a picture.  X-axis is a sample count.  We sample at 10hz.  OSR is 1 for all channels and we have the filter set to 16.

[BSTRobin]

Hi aparr001,

Could we know the background from you:
What is the layout of the sensor on the PCB?
How is the ventilation in structure?
What is the surrounding environment?

As you used 10 Hz sample rate and x-axis is sample count, the total recording time is 500 seconds?

[aparr001]

It is just in an office environment.  Even with capton tape over the port it does it.  So it is not an environmental effect.  In the software there is this delay we are told to calculate between consectutive measurements.  Our calculations came out to be 9ms (Oversamping is set to 1 for all measurements) we set req_delay_us to 9ms for m_bmeDev.delay_us(req_delay_us, m_bmeDev.inf_prt) fuction call.  When we changed this to 18ms the problem has gone away.  So it must be some timing related issue. 

[BSTRobin]

Hi aparr001,

The unit of this function delay_us() is microseconds.
If you need, we could upload example code on STM32 for your reference.