>The switch will cut the power if you draw less than 10mA (480 mW), so regardless of PHY efficiency [...] you are REQUIRED by the spec to generate heat that will mess up your sensor measurements.
Out of genuine curiosity, could you elaborate on this further, or share some sources I could read more on? I knew that was once the case, but my understanding was that significant improvements were made for the Maintain Power Signature (MPS) requirements with dual signature and PD standards in the 802.3bt update. According to [0], in the section on 145.3.9 PD MPS:
>"To further reduce minimum standby power consumption for PoE systems, Type 3 and Type 4 dual-signature PDs can make use of optimized MPS timings when connected to a Type 3 or Type 4 PSE, as shown in Figure 19. PDs assigned to Class 1 through 5 must draw a current of 10 mA for at least 7 ms with no more than 310 ms between pulses. This translates to an average power consumption of 12 mW per pairset, or about 1/10th (12 mW/ 124.6 mW ) of the Type 1 / Type 2 minimum pulse average power consumption."
So my assumption was that the spec had significantly improved on this front starting around 7 years ago? I mean, I'm aware that there can be a very, very great deal of lag time between specs and sufficiently cheap and developed new chipsets taking advantage, but I don't think that's the spec's fault either. In principle if the market was there (and yes, it isn't) the tech could meet it right? My extremely limited experience too is that typical wireless battery powered setups can be sensitive to heat as well in the few applications I've dealt with where it's significant, which makes me wonder if in practice in some cases it might be better to use an IR sensor aimed at a semi-closed or closed but air separated material with known (presumably as close to 1.00 as feasible?) thermal emissivity.
Still, there's lots of sensor use cases where it just doesn't matter, but it'd be nice to be able to hard wire+network on the cheap stuff that's very isolated from wireless signal and physically awkward to get at. I'm fully cognizant though that it's a dream unlikely to be realized, just a personal wish there was more PoE IOT stuff (and while we're at it with magical dream lands that it all had open fully local APIs and everyone worked on first class Home Assistant support and...).
Good luck finding reasonably priced switches and low power PD ICs that support type 3 or type 4 PoE.
Also, supporting those tiny pulses requires large capacitors to hold a charge in between pulses. That plus the required magnetics make PoE sensors way more bulky and expensive to manufacture than old fashioned RS-485 sensors.
Out of genuine curiosity, could you elaborate on this further, or share some sources I could read more on? I knew that was once the case, but my understanding was that significant improvements were made for the Maintain Power Signature (MPS) requirements with dual signature and PD standards in the 802.3bt update. According to [0], in the section on 145.3.9 PD MPS:
>"To further reduce minimum standby power consumption for PoE systems, Type 3 and Type 4 dual-signature PDs can make use of optimized MPS timings when connected to a Type 3 or Type 4 PSE, as shown in Figure 19. PDs assigned to Class 1 through 5 must draw a current of 10 mA for at least 7 ms with no more than 310 ms between pulses. This translates to an average power consumption of 12 mW per pairset, or about 1/10th (12 mW/ 124.6 mW ) of the Type 1 / Type 2 minimum pulse average power consumption."
So my assumption was that the spec had significantly improved on this front starting around 7 years ago? I mean, I'm aware that there can be a very, very great deal of lag time between specs and sufficiently cheap and developed new chipsets taking advantage, but I don't think that's the spec's fault either. In principle if the market was there (and yes, it isn't) the tech could meet it right? My extremely limited experience too is that typical wireless battery powered setups can be sensitive to heat as well in the few applications I've dealt with where it's significant, which makes me wonder if in practice in some cases it might be better to use an IR sensor aimed at a semi-closed or closed but air separated material with known (presumably as close to 1.00 as feasible?) thermal emissivity.
Still, there's lots of sensor use cases where it just doesn't matter, but it'd be nice to be able to hard wire+network on the cheap stuff that's very isolated from wireless signal and physically awkward to get at. I'm fully cognizant though that it's a dream unlikely to be realized, just a personal wish there was more PoE IOT stuff (and while we're at it with magical dream lands that it all had open fully local APIs and everyone worked on first class Home Assistant support and...).
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0: https://ethernetalliance.org/wp-content/uploads/2019/08/EA_P...