Unit weight is the main indicator in the quality standards for wheat procurement and transportation, and also an important basis for measuring the quality of other grains. Although the size of the bulk density meter has been uniformly measured using the HGT iooo~bulk density meter according to the regulations of GB 5498-85, differences in the production years, usage time, and maintenance of each bulk density meter can lead to differences in the sensitivity of the instrument's components (especially the pivot knife and key knife). Therefore, for the same sample, although the inspection personnel are proficient in operating according to standard methods, But the data measured by each weighing device also varies. According to the usage of more than 40 volumetric weighing machines in various factories and institutes in our city in recent years, the error generated by each volumetric weighing machine is as low as 2-3 grams per liter, up to more than 10 grams per liter. This not only affects the price execution during grain procurement and transportation, but more importantly, it directly affects the grade index of wheat during the provincial allocation process, causing unnecessary transportation disputes and causing economic losses to grain enterprises. Therefore, the calibration of the bulk density device is an important task in grain and oil inspection. For this reason, our city is able to conduct an annual calibration of the bulk density device used in the backup factory before the summer summer storage each year. Every year, 20 million kilograms of wheat from other provinces are adjusted, without any quality disputes caused by inconsistent bulk density. The tolerance error of the wheat adjusted is within the range of 3 grams per liter, as follows:

Firstly, register and number the density controllers of each unit, requiring that each unit's instruments be dedicated and that all components not be mixed with each other to avoid errors. Before installation, clean all components with tools such as gauze and a brush, and ensure that they are free of dust and debris,. For key components such as fulcrum knives, key knives, agate fulcrum knife holders, and key knife holders, gently brush and rub them without damaging the knife edge. For knife edges that do not have rust marks for a long time, first use cotton paste toothpaste to gently wipe them off, and then apply a layer of sewing machine oil. After all instruments are installed, perform zero calibration, and then perform calibration in two parts.

One is the calibration of the instrument measurement system. The method is to add a certain quality fourth level standard weight to the capacity of the measuring device, move the size of the slide hammer on the scale accordingly, and compare it with the data on the scale. The new instrument has been calibrated accurately before leaving the factory, so it is only necessary to check the H port according to this. However, there are also instruments that may deviate due to long service life or poor storage. This is mainly due to the leakage of lead blocks in the large and small slide hammers during disassembly or manual addition of lead blocks, At this point, perform calibration by adding or subtracting lead blocks into the large and small hammers until the mass of the standard weight placed in the volumetric cylinder is equivalent to the number reflected on the scale.

The second is to correct the measurement error (capacity part) of the instrument. At this point, wheat samples should be directly used for determination. The method is to select the same sample (with a unit weight range of 759-760 grams/liter), and use a standard unit weight device (or a calibrated unit weight device) to alternately measure each sample for 10 times. The data from the 10 measurements are averaged and the average value is calculated. The difference between the two averages is printed as the unit weight error between the calibrated instrument and the standard instrument during the measurement process