Originally posted by DeepThought
Although it's precision is only 1% which is a little disappointing.
I imagine that can be improved. I suspect the knife edge might add to the friction of the device and other processes like the precision of components in the current drivers come into play. If you used high precision op-amps and such, low bias amps, low noise and such, you could beat that number. They might be using electronics from the '60's, like the old 741 op amp or the 555 timer level. Cheap but noisy. You would need quiet and very linear devices.
The working end of the electronics side is like a loudspeaker transducer and would have it's own set of linearity problems to overcome to get to say 1/10th percent or so, like the windings of the coil would have to be very regular and clean and so forth.
I haven't looked at the exact specs but I bet it can be improved with a little help from modern op amps and feedback circuits.