The measurement standard is a measuring instrument that reproduces and preserves the unit of measurement and has the characteristics of a specified unit of measurement. In the field of geometric measurement, the cartoning production line can be divided into two types: length reference and angle reference. Angle reference: Angle and length are different. Since the common angle unit (degrees) is defined by the circumferential angle, that is, the circumferential angle is equal to 360°, and the radian has a conversion relationship with degrees, minutes, and seconds, so a natural benchmark for the angle is established.
According to different ways of obtaining measurement results, it can be divided into: direct measurement and indirect measurement. Obtain the measured value or the deviation from the standard value directly from the reading device of the measuring instrument is called direct measurement. Such as the use of vernier calipers, outer diameter micrometer to measure the shaft diameter, etc. By measuring the quantity that has a functional relationship with the measured one, the measured measurement obtained according to the known functional relationship is called indirect measurement. For example, the actual value of the arc radius can be obtained by measuring the corresponding arc height and chord length of an arc.