Hello guys! How are you doing? This is my first question here, so I hope it's not too obvious for you! =)

I've got a micro servo hxt900 and want to monitor the torque required to sustain its position when actuating on a small biped robot. Well, I plan on using the torque equation of the motor (Torque = kt * I), which would reduce the problem to a simple current measuring circuit. The problem is I can't find the value of 'kt'. The servo datasheet doesn't display any constant for this.

All I could do is calculate 'kt' by using the unloaded velocity of the motor and the velocity equation (because kt = 1/kv):

- From the datasheet:

(60/.12)º/s = 500º/s = 1.389 rps = 83.333 rpm @4.8V

- Considering:

Velocity = kv(rpm/volt)*V(volt)

- Then:

83.333 = kv(rpm/volt)*4.8 kv(rpm/volt) = 17.361 rpm/volt

- Now, if:

kt = 1/kv

- We would have:

kt = 0.0576

Is that result correct? If so, what would the units of it be? Also, why does the datasheet also relates voltage with torque (by telling the stall torque value @4.8V) if what realy influences torque is the current and not the tension?