Key advantages of Magnetic wire tensioners:

These magnetic tensioners use a device containing a permanent magnet as a non-contact method of generating a variable resistance to rotation of the main wheel of the tensioner, thus maintaining wire tension at the set value for longer periods than their mechanical counterparts with greatly reduced requirement for adjustment.
Type MTC100
Used for fine wire (no larger than 0.07mm at normal recommended wire tension)
Arm position gives feedback to the system, adjusting the main friction wheel to regulate and maintain constant wire tension during the coil winding cycle.
The tension setting is controlled by adjusting the lower knob, to ensure that the arm operates within its working limits.
Polished ceramic parts at each point of contact protect insulation and guide the wire.
Captive roller on tension arm is easy to thread, eliminates chance of losing wire.
Tension can be set using scale in grams 12gr - 120gr (~0.04mm-0.14mm)