The total indicator reading (TIR) is defined as what?

The total indicator reading (TIR) is correctly defined as the difference between the minimum and maximum readings obtained during a runout check. This measurement is significant because it provides a comprehensive view of the variance in a shaft or component's surface during rotation, indicating the extent of any imperfections or misalignments.

When conducting a runout test, the TIR value helps to assess how much the surface deviates from the ideal circular path, allowing technicians to identify whether the equipment is functioning within acceptable tolerances. A lower TIR value indicates better alignment and less runout, while a higher value suggests potential issues that might require corrective action.

The other options describe different concepts or calculations that do not accurately represent TIR. For example, the minimum reading on its own does not provide the range of variation, and an average reading may not accurately depict the maximum deviation present. Therefore, understanding TIR as the difference between the maximum and minimum readings is essential for effective equipment maintenance and assessment.