Two devices - same model same firmware, different parameters missing in data

Hi all,

I’ve got two devices (MileSight AM300 environment sensors) in different locations connected to different gateways. The sensors have 11 parameters they report on:

Temp, Humidity, Pressure, tVOC, Movement, Light, CO2, PM2.5, PM10, HCOC and O3

Both are the same firmware and model - one reports all the above but always misses O3, the other reports all the above but misses HCOC.

I’m wondering if this is something related to any kind of “soft limit” on parameters given it’s 10/11 and it’s consistent. Or if this is something more related to the LoraWAN MAC version? The device reports compatability with 1.1.0 but doesn’t advise what revision. Currently Set to 1.0.3A.

Hoping someone has an answer on this one.

you could also check CODEC, in case there’s a bug in there.

That’s the strange thing, it’s the same codec for both devices. I’d look deeper if it was the same ten parameters on both with the same one missing, but it’s different on each. It’s weird. I’m checking the Spread Factor as well, but my experience is that would break things into much smaller chunks like two or three parameters at a time. I can’t work it out!

Section 4.6.2 of device manual describes a “backup” feature, if you want to excluded difference in configuration. Manual states that channels may be turned off, which removes from display, but does not state whether same are left out from LoRa transmissions… Maybe you have these configured not to send some data?


  • I see these for around 300 USD - is that roughly what you paid?
  • I found it curious that brochure states that both HCHO & O3 electrochemical sensors need to be replaced every 2 years, but aforementioned manual lacks this information. Does this mean that you need to track this externally or does device alert you somehow?
  • Default reporting interval is 10 minutes, but usually air quality has a far longer time constant unless you’re in a clean room with very energetic air circulation.

The toolbox app they use to configure the device gives you a list of parameters it can detect, and you can turn these on and off which will ignore them in the payload. This is distinct from displaying their values on the sceen, so in answer to you, if they aren’t on the screen they are still sent in the payload unless you have turned off their inclusion in measuring. All parameters are on in my settings.

I hadn’t noticed that in brochure, I don’t think these have been on the market for more than six months, and while connected to the Helium network all parameters were reporting. The weird link is that the sensor for HCHO/O3 is actually the one component it seems weird that for one device it is sending one parameter, and the other device is sending the other. I’ve reached out to manufacturer about this as well.

It would appear the deployment scenario is for workplaces/offices and the like, I wouldn’t think they were appropriate for industrial use, they have another unit without display that seems to be for that purpose. With that in mind, I’d guess the intent is that there is some kind of airconditioning pushing air around, and it isn’t simply subject to brownian motion :wink:

I’ve no idea what they are worth, I’m doing systems integration with a loaner test unit sorry! I think they’re a pretty nice unit from what I’ve experienced with them, they seem happy to talk to Helium, MileSIght’s implementation of a LoraWAN server on their hotspots, and simply forwarding packets to an external platform like Chirpstack.

Well! mystery solved! Despite everything appearing as though it’s an all-in-one device. There are actually two! one only measures HCHO, the other only measures O3. I’m surprised there’s no mention of this at all in their material, data sheet, even manuals talking about payload structure etc.

To the unaware person, they are the dame device, same model same everything, but when you get two together there’s a “part number” one is PN: O3, the other is PN: HCHO. Shame I’ve wasted a day+ trying to sort this out :man_facepalming: thanks for your input @fmgst ! I hope you find this as amusing as I did :slight_smile: