The ratio of torque to the weight of the moving part of an instrument is known as a torque/weight ratio. This ratio affects the instrument’s sensitivity, and higher ratio instruments have more sensitivity.
If the deflecting torque acts as a force on the instrument and shows full-scale deflection, the torque/weight ratio of the moving part of the instruments should not be less than 0.1.
If a pointer has less weight, it will produce more deflecting torque. This means that even a slight deflection will cause the pointer to move and indicate the measured value.
Consider an indicating instrument to understand the concept of this ratio.
- When the weight of the instrument pointer is low, it means that the instrument possesses a high torque/weight ratio., which indicates that the pointer will deflect and display the measured value even with a small amount of deflecting torque.
- An instrument’s frictional torque is directly proportional to the weight of its moving part. The rotational force that causes friction between two objects is frictional torque. The weight of the moving part influences the magnitude of the frictional torque.
- The frictional torque is a crucial factor in determining the performance of instruments. The deflection of an instrument’s pointer is influenced by the fractional component of the frictional torque, and the direction in which the torque is applied also plays a role in determining the deflection.
- If the frictional torque is much smaller than the deflecting torque, the frictional torque can be neglected.
- The high torque-to-weight ratio of an analog instrument indicates low friction loss.