It is important to manufacture cameras in a conditioned environment. If there is too much dust, the camera could get contaminated. If the humidity is too low, image sensors could get damaged due to electrostatic discharge (ESD). Nowadays the room conditions in the factory are mostly electronically measured however in the past analog devices where used for this. We found some cool photos from instrumentation used in the past which shows how far we have come - all leading to more consistent, and better performing cameras.
The photo below shows one of these analog devices that has been used in our factory, a thermohygrograph. It measured humidity and temperature and the measurement was logged on a paper sheet rolled around the round cylinder visible on the left part of the photo.
Left: the complete thermohygrograph, middle: the winding mechanism of the cylinder, right: the hair bundles and the bimetallic spiral.
To let the round cylinder rotate you actually had to wind it up! No batteries or what so ever was required. It was thus a very environmentally friendly device.
The humidity was measured with hair bundles that extend in high humidity and shrink in low humidity. Did you know this principle for measuring humidity was already known in 1783?
The temperature was measured with a bimetallic spiral. Due to the difference in expansion coefficient between the metals a temperature change is transformed into a mechanical movement.
The modern measurement equipment is much more compact as you can see on the image below.