Views:170 Author:Site Editor Publish Time: 2020-12-24 Origin:Site
There are many types of scales，such as industrial scales and jewelry scales, but their essence is to weigh the mass of the measured object. Because of the different needs in different scenarios, scales have developed more types and functions to meet our weighing needs. Today, we will introduce some different types of scales.
The weighing balance, also including balance scale, beam balance, and laboratory balance, was the first mass measuring instrument invented. In its traditional form, it consists of a pivoted horizontal lever with arms of equal length – the beam – and a weighing pan suspended from each arm. Therefore, the plural name "scales" for a weighing instrument. Its weighing method is also the most traditional, but not extremely accurate. The unknown mass is placed in one pan and standard masses are added to the other pan until the beam is as close to equilibrium as possible. In precision balances, a more accurate determination of the mass is given by the position of a sliding mass moved along a graduated scale. Technically, a balance compares weight rather than mass, but in a given gravitational field, the weight of an object is proportional to its mass, so the standard masses used with balances are usually labeled in units of mass.
An analytical balance is a class of balance designed to measure small mass in the sub-milligram range, which is always used in the laboratory. The measuring pan of an analytical balance (0.1 mg or better) is inside a transparent enclosure with doors so that dust does not collect and so any air currents in the room do not affect the balance's operation. This enclosure is often called a draft shield. The use of a mechanically vented balance safety enclosure, which has uniquely designed acrylic airfoils, allows a smooth turbulence-free airflow that prevents balance fluctuation and the measure of mass down to 1 μg without fluctuations or loss of product. Also, the sample must be at room temperature to prevent natural convection from forming air currents inside the enclosure from causing an error in reading. Single-pan mechanical substitution balance maintains consistent response throughout the useful capacity is achieved by maintaining a constant load on the lab analytical balance beam, thus the fulcrum, by subtracting mass on the same side of the beam to which the sample is added.
A spring scale measures mass by reporting the distance that a spring deflects under a load. This contrasts with a balance, which compares the torque due to a sample weight to the torque on the arm due to a standard reference mass using a horizontal lever. Spring scales measure force, which is the tension force of constraint acting on an object, opposing the local force of gravity. They are usually calibrated so that measured force translates to mass at earth's gravity. The object to be weighed can be simply hung from the spring or set on a pivot and bearing platform.
In a spring scale, the spring either stretches or compresses. By Hooke's law, every spring has a proportionality constant that relates how hard it is pulled to how far it stretches. Weighing scales use a spring with a known spring constant and measure the displacement of the spring by any variety of mechanisms to produce an estimate of the gravitational force applied by the object. Rack and pinion mechanisms are often used to convert the linear spring motion to a dial reading.
Spring scales have two sources of error that balances do not: the measured mass varies with the strength of the local gravitational force (by as much as 0.5% at different locations on Earth), and the elasticity of the measurement spring can vary slightly with temperature. With proper manufacturing and setup, however, spring scales can be rated as legal for commerce. To remove the temperature error, a commerce-legal spring scale must either have temperature-compensated springs or be used at a fairly constant temperature. To eliminate the effect of gravity variations, a commerce-legal spring scale must be calibrated where it is used.
In order to meet private requirements, kitchen food scales and smart kitchen scales have been developed to be used in family kitchens. Scales bring measurement and value.