The device for detecting the spring hammer in the pressure calibration table becomes a calibration device. Since there is no corresponding verification procedure at present, a calibration certificate should be issued, and the calibration certificate stipulates that there should be a description of the uncertainty of the measurement result. The "Measurement Standards for Measurement Standards" requires "N-repeated measurement times, N should be as large as possible, generally not less than 10 times. If the uncertainty introduced by the repetitiveness is not the main factor in the measurement uncertainty of the verification or calibration results. The component allows the appropriate number of repeated measurements to be reduced, but at least N>=6". The use of the pressure checker calibration device emphasizes that “the impact element should be turned to a different position after each operation. The average of the three readings on the calibration device can be used as the actual value of the impact energy of the measured spring hammer.” Therefore, the number of repeated measurements is insufficient.
The measured value of the impact kinetic energy of the pressure checker spring hammer calibration device produced at home and abroad adopts the dial pointer type reading, and the reading error is too large due to the limitation of the dial size and the pointer diameter. There are two reasons for this.
(1) The division value is large. Since the impact kinetic energy of the spring hammer of the pressure checker is small, the small-scale division of 2J on the disc by the principle of potential energy is difficult to achieve. At present, the German version of the German PTL company's pressure calibration table spring hammer calibration device has a graduation value of 0.02J, the scale line spacing is about 1MM, and the scale value of the spring calibration device of the pressure calibration table produced by a few domestic enterprises. For 0.01J, the tick spacing is less than 1MM. Taking the 0.14J spring impactor as an example, the accuracy of the calibration device is calculated as 3%, and the division value should be 0.004J, which is difficult to achieve in the subdivision tick line within the 1MM pitch on the dial.
(2) The large diameter of the pointer affects the reading. In the calibration device produced at home and abroad, 0.7MM piano wire is used as the pointer, and the 0.7MM pointer occupies 2/3 space with only 1MM spacing between the two tick marks, which results in a large estimation error. Even if the scale is subdivided between the scale lines with a spacing of only 1MM, the index value is increased. However, due to the influence of the 0.7MM pointer, the index value is smaller and the error is still large.
Through the above analysis, the spring hammer calibration device in the pressure calibration table can not meet the calibration of all spring hammers. At the same time, the calibration methods and calibration devices are different because there is no uniform calibration specification for metrology institutions all over the country. Therefore, in order to improve product quality, strengthen measurement management, and make the appliance have a unified calibration specification nationwide, it is very important to develop a scientific and effective pressure calibration table calibration device.
