Does anybody know how they actually do it without a fan and a defined volume around it? The marketing fluff says "It applies sophisticated algorithms to measure the PM2.5 concentration directly in free space, without requiring a fan", so I assume the main difference to traditional PM sensors is the software?

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dist-epoch 4 days ago | parent | next [-]

They have some tech specs: https://www.bosch-sensortec.com/media/boschsensortec/downloa...

> Laser light is emitted from the sensor and focused by the sensor lens at approximately 5 mm from the top of the sensor’s lens surface.

> Particles traveling in free space due to the natural ambient airflow are detected when passing through the laser focal (sensitive) region.

> Due to the interaction between particles and light, the light scatters in different directions; a fraction is back-scattered towards the sensor, where the integrated photo-detectors detect it.

> The back-scattered signal is processed by unique algorithms (based on particle counts, particle relative velocity, probed air volume during measurement) to derive the particulate matter mass concentration.

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trailbits 4 days ago | parent [-]

That's pretty much how all laser particle counters work... except the good ones use a fan and a chamber. Guess we'll have to wait and see how this compares to the reference sensors.

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ImaCake 4 days ago | parent [-]

Yep, I suspect this is all marketing fluff and no substance. I see a lot of superlatives but no substantial technical breakthrough here.

	▲	hakonjdjohnsen 4 days ago \| parent \| next [-]
		I think there is at least some plausible interpretation of this that points to more than marketing fluff. You want to count particles per volume of air, so conventional sensors use a fan to have a constant volumetric flow and then count particles per second to infer particles per volume. The way I interpret the above marketing language is that they use the optical sensor not only to count particles but also to measure the particle movement and infer airflow. So as long as there is some natural movement in the air, they can measure both particle count and volumetric flow, and thus infer particles per volume.
	▲	felixg3 2 days ago \| parent \| prev \| next [-]
		This is Bosch and not some random startup. It’s for sure a substantial technical breakthrough of integration, miniaturization, and if coming from Bosch, certainly enterprise and clinical-grade ready.
	▲	f1shy 4 days ago \| parent \| prev [-]
		I’m pretty pretty sure it is just marketing

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ethan_smith 4 days ago | parent | prev | next [-]

These fanless PM sensors typically use thermal convection to create natural airflow across the sensing area, combined with advanced signal processing to compensate for variable flow rates and environmental conditions.

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svilches 3 days ago | parent | prev | next [-]

Insider here: the technology inside is very cool and uses completely novel HW. I asked my PR colleagues for the release of more technical information.

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trailbits 4 days ago | parent | prev | next [-]

Also wonder how the sensor can stay clean without a fan. I suppose mounting upside down would help. Other fanless designs require periodic cleaning.

	▲	dist-epoch 4 days ago \| parent [-]
		The integration picture shows an "optical cover" transparent surface. I guess it's not meant to be used in highly contaminated areas.

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TimByte 4 days ago | parent | prev | next [-]

My guess is they're relying on natural air convection and using a more sensitive optical setup to compensate for the lack of forced airflow

	▲	f1shy 4 days ago \| parent [-]
		They don’t give lots of heat, so convection is negligible.

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f1shy 4 days ago | parent | prev [-]

Lying?

	▲	rurban 3 days ago \| parent [-]
		Marketing. Still a good sensor, just not as good as the ones with a fan. We didn't use this one