Abstract: A portable air tool for applying torque to a workpiece includes a built in strain gauge transducer for measuring applied torque and a built in potentiometer adjustment mechanism for balancing or calibrating the transducer in unloaded condition. The transducer and potentiometer adjustment mechanism are electrically connected by leads passing from the tool to an electrical circuit containing the power supply and a millivolt meter or computer. To balance the transducer in unloaded condition, the end of a screwdriver or other tool may be inserted through a housing aperture and into the air tool to turn an adjustment screw on the enclosed potentiometer until the millivolt meter reads zero indicating balance in the transducer circuit. Alternatively, the potentiometer could be mounted in a threaded sleeve forming the handle of the tool, with adjustment access to the potentiometer being provided when the handle is unthreaded and axially moved relative to the tool to expose the potentiometer.