First, the principle of the spring balance
Using the spring under the action of the gravity of the measured object A weighing instrument that deforms to measure the amount of a substance. The spring has the characteristic of deforming corresponding to the external force after being stressed. According to Hooke’s law, the amount of deformation of the spring within the elastic limit is proportional to the magnitude of the applied force. When weighing, the elastic force generated by the deformation of the spring is in balance with the weight (gravity) of the measured object, so the weight of the measured object can be measured from the amount of deformation, and then its mass can be determined. Spring scales can weigh from 1 mg to tens of tons. Among them, if the load is below 2mg, use quartz wire spring; if the load is below 5g, use flat coil spring; if the load is larger, use coil spring and disc spring. A common spring scale is a spring case scale made with a coil spring. After the measured object is put into the weighing pan, the coil spring is stretched under the action of the measured object’s gravity, and the lever device makes the rack move in a straight line to drive the gear pointer shaft to rotate. When the elastic force generated by the tension of the spring is balanced with the gravity of the measured object, the pointer will indicate the weight value of the measured object on the dial. The spring balance has the advantages of simple structure and intuitive reading. However, because the spring has the characteristics of elastic hysteresis and is easily affected by changes in external conditions such as temperature, its accuracy and sensitivity are low. In addition, its weighing results are also different due to the different acceleration of gravity.
Second, the use of spring scales
Before using a spring dynamometer, you must recognize its structure, mainly including springs, pointers, iron rods and hooks, etc. Wait.
(1) First of all, the measuring range must be clear, and the force to be measured cannot exceed its measuring range. Because the spring has a certain elastic limit, the measurement beyond this limit is inaccurate, and the measuring force may be damaged. count.
(2) The division value of the spring dynamometer should be clearly seen before measurement, so that it can be read during measurement.
(3) Before measuring, check whether the pointer points to the zero-scale line. If it does not point to the zero-scale line, adjust it so that the pointer points to the zero-scale line.
(4) Before use, gently pull the hook of the spring dynamometer back and forth to prevent the pointer from being stuck, which will bring greater error to the measurement.
(5) When measuring, the force of pulling the hook of the spring dynamometer should be parallel to the shell of the dynamometer, to avoid twisting and friction, and minimize the measurement error caused by friction.
(6) Wait until the reading is stable before reading, and the line of sight should be perpendicular to the surface of the scale panel during reading.
