Laser Counters

Dependable source of PMS5003 counters vs. hit or miss AliExpress adventures

Yes, you can buy a supply of these sensors directly from China, but PurpleAir tests the lots of sensors they ship out so you have a good chance of problem free counter replacement at maybe 10% of the original cost of the PA-II+ sensor per year. I only have one PA-II+ sensor, so I'm OK keeping spare counters ready to drop in when counts go wacky and cleaning doesn't help. On paper the newer dual laser based counters for the newer PurpleAir sensors should require 1/4 or fewer repairs, but annual repairs are OK. At first I thought the "flat shipping" was pricy, but 2nd day FedEX was a pleasant surprise.

laser counters work great but adapter kit hard to install

i needed to replace the sensors on an old PAII. purpleair support recommended the adapter kit. i found the kit hard to install. the YT video was difficult to follow because of constantly shifting point of view. also, i had to exert a lot of force to get everything to fit into the old PAII shell. the adapter kit is a good idea but it could have been made a lot more intuitive, as well as avoiding the fit issue. there were no text or printed instructions. i think if they had tried to create printed instructions, they would have seen the need to simplify the process.

Switch out sensors

It was easy to switch out the lasers in the sensor. I got tech support to wipe the data so I could use it at a different location. I was able to re-register it and the sensor is working.