I note that the ZH03A sensor shown in the specs is no longer in production and what is being sold is the ZH03B. Can I safely assume this is a drop-in replacement? I while waiting a month to get one from RO, I just bought one from China through Amazon and have it in hand.
On this subject: my failed unit is showing 850/1000/1000 ug/m3. I believe a failed laser diode will cause the unit to read full-scale on all particle sizes. As far as I can tell from available spec sheets, the full scale value should be 1000 for all particle sizes. What is the reason the PM1.0 is reading 850 instead of 1000?
OK – answering my own question. The B unit has a bigger fan than the OEM “A” unit. The attached photo shows the old one on the left and the new one (already connected) on the right.
As it was, the OEM did not fit very well either. It was *very* difficult to get it out of the case.
To get the new one in I decided to cut off piece of the circuit board, remove two of the screws holding the fan on and file down one corner of the PM unit.
The result is shown in the last photo where some white space is left so you can see how it fits. It is quite impossible to mount the PM unit on top of the PCB, as both the -A and B versions are the same height as the enclosures. I have no idea how uRad was able to get the PM unit in there originally.
It has been running for a bit over ah hour now and looks like it will be OK.