The first assembled PCBs were a beauty:

The sensors fitted the sockets perfectly. After spending a few hours trying to access sensor data, it became clear that unfortunately, the device didn't work. On each of the 4 electrochemical sensors, the voltage output was a constant value, no matter the fluctuations in test gases (SO2).

What happened was that I did a mistake when drawing the sensor footprint for the PCB design: the positions were mirrored, so the pins were all wrong. A stupid mistake that rendered the PCBs useless.

I had no choice but to start over again. The PCBs were redesigned with the proper sensor footprint, and some additional improvements I had in mind.

This time the performance was as expected. Putting everything together was fun - the PCB connectors and the aluminium enclosure holes fitted perfectly:

Looking good so far!