From: jeroen@nospam.please
On 12/27/25 01:35, Phil Hobbs wrote:
> Jeroen Belleman wrote:
>> On 12/26/25 11:37, Don Y wrote:
>>> On 12/26/2025 3:27 AM, Liz Tuddenham wrote:
>>>> Don Y wrote:
>>>>
>>>>> Any pointers regarding deployment of pressure sensors measuring
>>>>> air pressure?� I'm looking at nominally an inch of water
>>>>> (pressure/vacuum)...
>>>>
>>>> Washing machine/diswasher water-level switches?
>>>
>>> No, I'm looking at pressures in air handling systems.
>>>
>>> In systems that I've designed previously, someone
>>> else selected (very expensive!) transducers and
>>> I just had to interface with them.
>>>
>>> But, those were industrial systems with dedicated
>>> staff to keep them running, calibrated, etc.� You
>>> cared about the actual "numbers" from the sensors
>>> because you were controlling "regulated" processes
>>> and needed to document compliance/exceptions.
>>>
>>> I'm trying to leverage some of those algorithms but in a
>>> cheaper consumer market where stuff "just has to work".
>>> I don't care about numbers as much as *trends*, using
>>> adaptive algorithms to sort out what's "normal" from
>>> "indicating".
>>>
>>
>> I've had some fun with teeny tiny BME280 sensors. They
>> have a sub-1% absolute accuracy and enough resolution
>> to detect the pressure change between your head and your
>> feet. They measure temperature and humidity too. The
>> interface is I2C.
>>
>> Jeroen Belleman
>>
>
> Of course they might be detecting the difference in the mean molecular
> weight of the local atmosphere. ;)
>
> Cheers
>
> Phil Hobbs
>
>
Grmpf ;-)
While I was graphing the outputs, I was surprised by the efficiency
of humidity readings to detect human presence. The curve was quite
smooth with no one in the room, but got quite noisy with someone
present.
jeroen Belleman
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