Any socket spanner can be converted into a digital torque wrench,, by bonding a pair of shear gages such as the Micro Measurements type EA-06-062TV-350 on the stem of the spanner, and connecting them as a full bridge to a Model P3 strain Indicator and recorder made by Micro Measurements.
A simple calibration needs to be done, by locking the socket spanner in a vice so that the stem' and handle are both horizontal, balancing out the reading to zero on the Model P3, then hanging a weight on one end of the handle. The distance from the axis of the stem to the point where the weight is hung, is multiplied by the weight to get the applied torque on the spanner. The sensitivity on the model P3 can be changed to set the reading to the applied torque. This calibrates the entire system to indicate the torque when the spanner is used to tighten a bolt.
Model P3 can record the torque readings and send them to a computer through its USB port for storage of the data.
For details of the straingage and model P3, please see:
www.vishaypg.com/micro-measurements.