... which suggests, the variations that we see are probably down to variations in lighting, procedure, alignment and so on, rather than some inherent failure of the chrono to deliver a correct result.
When you think about it, the gap between the two sensors is unlikely to move by much; after all, the sensors are fixed in position. The quarz clock is unlikely to vary; quarz is used as a reference material. The Skan does need more than 12 volts as the internal reg cuts the incoming voltage to what the hardware needs. Other than that, it's alignment and lighting and pellet weight variation etc.