Upgraded planetary gearbox , comprising: - at least one input support provided with at least one input transmission element axially rotatable and connectable to an external appliance; - at least one output support provided with an output transmission element axially rotatable and connectable to an external appliance or to an external tool; - at least a first planetary wheelwork and at least a second planetary wheelwork both operationally placed between said input transmission element and said output transmission element ; - at least the first planetary wheelwork operationally connected to said input transmission element , comprising a first axially rotatable sun pinion , a first external static gearwheel having internal toothing, a first rotatable satellite holder provided with a plurality of first axially rotatable satellite gears engaged between the first sun pinion and the internal toothing of the first external static gearwheel ; - at least the second planetary wheelwork operationally connected to said output transmission element , comprising a second axially rotatable sun pinion , a second external static gearwheel having internal toothing, a second rotatable satellite holder provided with a plurality of second axially rotatable satellite gears engaged between the second sun pinion and the internal toothing of the second external static gearwheel , characterized by the fact that it comprises - a static coupling member fixed to said input support by interposition of said first planetary wheelwork and fixed to said output support by interposition of said second planetary wheelwork , wherein said static coupling member is locked together with said first external static gearwheel of said first planetary wheelwork and with said second external static gearwheel of said second planetary wheelwork ; and by the fact that said static coupling member comprises at least one measuring sensor for measuring the drive torque transmitted by said output transmission element . - at least one input support provided with at least one input transmission element axially rotatable and connectable to an external appliance; - at least one output support provided with an output transmission element axially rotatable and connectable to an external appliance or to an external tool; - at least a first planetary wheelwork and at least a second planetary wheelwork both operationally placed between said input transmission element and said output transmission element ; - at least the first planetary wheelwork operationally connected to said input transmission element , comprising a first axially rotatable sun pinion , a first external static gearwheel having internal toothing, a first rotatable satellite holder provided with a plurality of first axially rotatable satellite gears engaged between the first sun pinion and the internal toothing of the first external static gearwheel ; - at least the second planetary wheelwork operationally connected to said output transmission element , comprising a second axially rotatable sun pinion , a second external static gearwheel having internal toothing, a second rotatable satellite holder provided with a plurality of second axially rotatable satellite gears engaged between the second sun pinion and the internal toothing of the second external static gearwheel , characterized by the fact that it comprises - a static coupling member fixed to said input support by interposition of said first planetary wheelwork and fixed to said output support by interposition of said second planetary wheelwork , wherein said static coupling member is locked together with said first external static gearwheel of said first planetary wheelwork and with said second external static gearwheel of said second planetary wheelwork ; <EOS>