Method for expressing the accuracy level of belt weighers

According to current international recommendations (OIML R50:1996), national metrological verification regulations (JJG195-2002), and national standards (GB/T 7721-2007), electronic belt scales are set with three accuracy levels of 0.5, 1, and 2, which require that the dynamic cumulative error of their automatic weighing of materials during use inspection should not exceed 0.5%, 1%, and 2%, respectively. The allowable error during initial and subsequent verification should be half of the aforementioned indicators, that is, not more than 0.25%, 0.5%, and 0.5%, respectively 1%. That is to say, when referring to the accuracy of a scale, it should be equivalent to the long-term allowable error.

The significance of measuring the length of a belt scale

The physical meaning of the weighing length (L) is the length of the material that has an equivalent effect on the symmetry when passing through a belt scale. When the material is in the area of that length, its weight is fully transmitted to the weighing sensor (and support point); When the material is outside the area of that length, the weighing sensor (and support point) is not affected by the gravity of the material.

For conveyor type belt weighers, all the weight of the material on the positive belt is transmitted to the weighing sensor (and support point) through the force transmission mechanism, so the weighing length is equal to the center distance between the head and tail wheels.

For weighing desktop conveyor belt scales, during the process of material entering the rear scale end support roller and leaving the front scale end support roller,The weighing sensors are affected by the weight of the material; Even the belt runout and tension changes within 3-5 roller intervals before and after the two scale end rollers can have an impact on the sensor, so this section is called the weighing domain. However, the weight of the material is not completely transmitted to the sensor anywhere within the weighing range. Before the material reaches the first weighing roller or after it has driven away from the last weighing roller, the weight of the material is borne jointly by the weighing roller and the weighing end roller, and the force on the weighing end roller is not transmitted to the sensor (and support point). The concept of weighing length and weighing domain is not the same, but rather refers to the material transferring all weight to the sensor within the length of the belt scale, hence it is also called the equivalent weighing segment. The description of the weighing length of the OIML R50 for the weighing desktop carrier belt scale is:& Ldquo; For a multi roller belt scale, it is the distance L0 between the weighing rollers at both ends of the weighing platform, plus half of the distance La and Lb between the roller and the adjacent weighing rollers; For a single roller belt scale, the weighing length is half of the distance L1 between the front and rear roller ends of the scale& Amp; Rdquo;

In fact, it is not difficult to derive a more concise unified expression:& Ldquo; The half of the sum of the distance between the front and rear weighing rollers and the distance between the first and last weighing rollers (for a single roller belt scale L0=0) is 1/2 (L1+L0)& Amp; Rdquo;
Guangzhou Zhongxin Automation Technology Co., Ltd. provides customers with relevant solutions for belt scales. If you need further information, please contact our sales manager: Manager Chen, hotline: 18520271262, or visit our official website for relevant cases:& Ldquo;Belt scale - Zhongxin is a first-class company in the sales field of belt scale sensors”