According to the measurement method: 1) Direct measurement When measuring with a sensor meter, the meter readings can be directly represented by the calculations without any calculations, which is called direct measurement. For example, measuring the current of a circuit with a magneto-electric ammeter and measuring the pressure of the boiler with a spring-tube type pressure gauge is a direct measurement. The advantage of direct measurement is that the measurement process is simple and rapid. The disadvantage is that the measurement accuracy is not easy to achieve. This measurement method is widely used in engineering. 2) Indirect measurement Some measurements are impossible or inconvenient to measure directly. This requires that when using the meter for measurement, first measure several quantities that have a definite functional relationship with the measured physical quantity, and then substitute the measured value into the functional relationship. The desired result, this method is called indirect measurement. For example, to measure the density Ï of a cuboid in units of kg/m3, it is obviously impossible to directly obtain the magnitude of such a unit, but the length, width and height of the cuboid can be measured first, ie, a, b, c (unit It is m) and its mass m (in kg), and then the density is obtained according to the following formula: 3) Indirect measurement is more than the amount required for direct measurement, and the calculation process is complicated, and there are many factors causing errors. However, if the error is analyzed and the optimized measurement method is selected and determined, it is carried out under ideal conditions. Indirect measurement, the accuracy of the measurement results is not necessarily low, and sometimes high measurement accuracy can be obtained. Indirect measurements are generally used in situations where it is inconvenient to measure directly or lack direct measurement. 4) Combined measurement When measuring with a sensor meter, if the measured physical quantity must pass the solution of the simultaneous equations to obtain the final result, then the measurement is called a combined measurement. When performing combined measurements, it is generally necessary to change the test conditions in order to obtain the data needed for a set of simultaneous equations. Combined measurement is a special precision measurement method. The operation procedure is complicated and takes a long time. It is generally suitable for scientific experiments or special occasions. According to the measurement method: 5) Differential measurement The differential measurement is a measurement method that combines the advantages of the deviation measurement and the zero measurement. It will be measured and compared to the known standard amount, and the difference will be measured and then measured by the deviation method. Therefore, the advantage of this method is that the reaction is fast and the measurement accuracy is high, which is especially suitable for the measurement of online control parameters. 6) Deviation measurement The displacement of the meter pointer (ie, the deviation) determines the measured value. This measurement method is called the deviation measurement. When applying a deviation measurement, the meter scale is previously calibrated with a standard instrument. During the measurement, the input is measured and the value measured is determined according to the indication value on the scale indicated by the meter pointer. The measurement process of this method is relatively simple and rapid, but the measurement results are less accurate. 7) Zero measurement The zero position measurement uses the zero position indication of the zero meter to detect the balance state of the measurement system. When the measurement system is balanced, the measurement method of the measured quantity is determined by the known standard quantity. When using this measurement method for measurement, the known standard quantity is directly compared with the measured quantity, and the known quantity should be continuously adjustable. When the zero meter means, the measured quantity is equal to the known standard quantity. For example, a balance, a potentiometer, and the like. The advantage of zero-position measurement is that it can obtain relatively high measurement accuracy, but the measurement process is complicated, and it needs to be balanced when measuring. It takes a long time and is not suitable for measuring fast-changing signals. 8) According to measurement accuracy During the whole measurement process, if all the factors (conditions) that affect and determine the measurement accuracy are always the same, if the same instrument is used, the same method is used to perform repeated measurements on the same measurement under the same environmental conditions. , called equal precision measurement. In practice, it is difficult to achieve that all of these factors (conditions) remain constant, so in general they are only approximated as equal precision measurements. Repeated measurements on the same measurement with different precision gauges or different measurement methods, or where environmental conditions vary widely, are called non-equal precision measurements. 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Pressure sensor detection method
The measurement methods of pressure sensors are classified according to means: direct measurement, indirect measurement and combined measurement; according to the measurement methods: differential, deviation and zero measurement; according to measurement accuracy classification: equal precision and non-equal precision measurement According to the change situation, there are: dynamic and static measurement; according to whether the sensitive components are in contact with the measured medium: contact and non-contact measurement. Details are as follows: