Features of Direct Measurement Technology and Indirect Measurement Technology

Direct measurement is a measurement technique in which the measuring tool is directly compared with the measured data, so that the measured data can be directly obtained from the measurement process or from the measuring tool (instrument, meter, etc.) directly (not through calculation and other processes). That is, it is not necessary to measure other quantities that have a functional relationship with the measured value, but can directly obtain the measured value of the measurement method. Note: (1) In order to make the corresponding direct measurement, it is to use the 'measuring tool' to directly compare with the measured, so that it can be directly (not through the calculation process) from the measurement process or from the 'measuring tool' (instrument, meter, etc.) Measurement technology that directly obtains the measured data. That is, it is not necessary to measure other quantities that have a functional relationship with the measured value, but can directly obtain the measured value of the measurement method. Note: (1) In order to make corresponding corrections, supplementary measurements or calculations are required to determine the value of the influence quantity. This measurement method is still a direct measurement. (2) According to the displayed value of the measuring instrument, the measurement of the measured value must be confirmed by checking the chart, which is also a direct measurement. Example: (1) Measuring the liquid volume with a graduated cylinder; (2) Measuring the mass of an object with an equal arm balance. Its characteristic is: if the accuracy of the measuring tool is guaranteed, the accuracy of its measurement is very high. 2. Indirect measurement technology means that the measuring tool is not directly compared with the measured (measurement) during measurement, but the measuring tool is used to obtain other quantities that have a definite functional relationship with the measured in the process of comparison (measurement), and then use it. After these quantities are calculated by functional relations, the measurement technique to be measured is obtained. That is, the measurement method of the measured value can be obtained by measuring other quantities that have a functional relationship with the measured value. Example: a. Determine the rectangular area by measuring the length; b. Determine the resistivity by measuring the conductor resistance, length and cross-sectional area. Its characteristic is: the uncertainty of measurement is not only determined by the certainty of various measuring tools, instruments, etc., but also determined by the connection method of the line and the scientificity of the calculation formula. So try to use the direct measurement method as much as possible, and only consider using the indirect measurement method where there is no way to use direct measurement.