A new high-accuracy counter-type tachometer

THE EFFICIENCY of some present-day power equipment such as steam turbines, gas turbines, electric motors, and others has reached the point where further efficiency increases may be of the order of one per cent or less due to a particular design change. Since the output of a prime mover is obtained from torque and speed, these two quantities must be measured with high accuracy for accurate efficiency results. Present standard tachometers are simple in principle but reach a maximum useful accuracy of about one per cent. Often, however, the over-all probable inaccuracy is greater than the small change in efficiency expected due to a design change.