Mechanical quantity measuring instruments refer to industrial automation testing instruments that measure mechanical quantities such as size, displacement, force, weight, torque, speed, and vibration. They are generally composed of sensors, measuring circuits, indicators, and auxiliary power sources.

The selection of measuring instruments should be based on technical and economic considerations, so that their type and specifications are suitable for the shape, position, size, and measured parameter characteristics of the workpiece. The metrological characteristics (such as allowable error, stability, measurement range, sensitivity, resolution, etc.) should appropriately meet the predetermined requirements, be sufficient but not too high, and be considered simultaneously with the selection of measurement methods.

1. According to the processing batch of the workpiece: for small batches, ordinary measuring instruments should be used; Select gauges and inspection fixtures in large quantities to improve measurement efficiency.

2. According to the structure and weight of the workpiece: small and simple workpieces can be measured on a measuring instrument, while large and complex workpieces require an upper mounted measuring instrument, which means the measuring instrument is taken to the workpiece for measurement.

3. Determine the specifications of the measuring instrument based on the size and requirements of the workpiece. To ensure that the measuring range of the measuring instrument can accommodate the workpiece, the measuring head can extend into the measured part.

4. Select measuring instruments based on the required error (tolerance) of the workpiece. The allowable error of measuring instruments is usually 1/3 to 1/10 of the workpiece tolerance. If the measured workpiece belongs to the measuring equipment, its tolerance of 1/10 must be selected; If the tested workpiece is a general product, its tolerance should be selected from 1/3 to 1/5; If the conditions of the measuring instrument do not allow it, it can also be 1/2 of its tolerance, but at this point, the confidence level of the measurement results will correspondingly decrease.

5. When selecting sensitivity, it should be noted that if the sensitivity of the measuring instrument is too low, it will affect the measurement accuracy, and if it is too high, it will be difficult to achieve equilibrium in a timely manner.