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# What Types in Pressure Sensor Measurement Method

There are 10 types of measurement methods for pressure sensors under most application conditions. The method used for the pressure sensor in measurement is very important to the entire inspection system, which will directly affect whether the measurement task can be completed successfully. In this regard, it is necessary to analyze the different measurement purposes and specific conditions to find a practical way.
According to measuring means, measurement methods of pressure sensors are classified into direct measurement, indirect measurement, and combined measurement. According to measuring ways, it can be divided into minor- difference measurement, deviation measurement and zero position measurement. According to measuring accuracy, there are equal accuracy measurement and non-equal accuracy measurement. According to pressure change, there are dynamic measurement and static measurement. According to whether the sensitive component is in contact with the measured medium, there are contact measurement and non-contact measurement.

I.
According to measuring means
• Direct measurement
Direct measurement means that when using the pressure sensor for measurement, the meter's readings can directly represent the results required for the measurement without any calculations. For example, measuring the pressure of a high-temperature liquid with a high temperature pressure sensor, and measuring the pressure of water and viscous liquid with a diaphragm pressure sensor are direct measurements. The advantage of direct measurement is that the measurement process is simple and rapid, and its disadvantage is that the measurement accuracy is not easy to reach very high. This method is widely used in engineering.
• Indirect measurement
Some measured quality are impossible or inconvenient be measured directly. This requires that when using a pressure sensor for measurement, first measure several quantities that have a determined functional relationship with the measured physical quantity. Then substitute the measured value into the functional relationship, and the desired result is obtained through calculation. This method is called indirect measurement. For example, to measure the density ρ of a cuboid in units of kg / m3, it is obviously not possible to obtain the magnitude in this unit directly. We can first measure the length, width and height of the cuboid, that are a, b, c (in m) and its mass m (in kg), then calculate the density according to the density formula.
Compared with direct measurement, indirect measurement requires much measured quality, and the calculation process is complicated so the factors causing errors are more. However, if we analyze the error as well as select and determine the optimized measurement method, then perform the indirect measurement under ideal conditions. The accuracy of the measurement result is not necessarily low, and sometimes a high measurement accuracy will also be obtained. Indirect measurement is generally used in situations where it is inconvenient to measure directly or lack direct measuring means.
• Combined measurement
When using a pressure sensor for measurement, if the measured physical quantity must be solved by the simultaneous equations to obtain the final result, then the measurement is called combined measurement. When performing combined measurement, it is generally necessary to change the measurement conditions in order to obtain the data required for a set of simultaneous equations. For combining a special precision measurement method, the operation procedure is complicated and takes a long time so it is generally suitable for scientific experiments or special occasions.

II. According to measuring ways

• Minor-difference measurement
Minor-difference measurement is a measurement method that combines the advantages of the deviation measurement and zero-position measurement. This method compares the measured quantity with a known standard quantity, and after taking the difference, the difference is 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 specification measurement in online control.
• Deviation measurement
The displacement of the meter pointer (the deviation) is used to determine the measured value. This measurement method is called the deviation measurement. When using the deviation measurement method, the scale of the pressure sensor needs to be calibrated in advance using a standard instrument. In measurement, input the measured quality and determine the measured value according to the indication on the scale marked by the pointer of the sensor. This method makes the measurement process simpler and faster, but the measurement results are less accurate.
• Zero-position measurement
Zero-position measurement is a measurement method that determines the measured value with a known standard amount when measuring the system balance. Detecting the balance state of the measurement system with the zero indication of the zero gauge. When measuring with this method, the known standard amount is directly compared with the measured quality. The known amount should be a continuous quantity. When the zero gauge refers to zero, the measured value is equal to the known standard amount. The advantage of zero-position measurement is that we can get higher measurement accuracy. However, the measurement process is complicated, and requires a balanced operation as well as takes a long time. It is not suitable for measuring signals that change rapidly.

III. According to measuring accuracy

• Equal accuracy measurement
During the measurement process, if all factors (conditions) that affect and determine measurement accuracy remain constant. Use the same pressure sensor to repeat the measurement for the same measured quality under the same environmental conditions in the same way. This measurement method is called equal accuracy measurement. In practice, it is very difficult to remain these factors (conditions) all be the same. Therefore, in general, it is only approximately considered to be an equal accuracy measurement.
• Non-equal accuracy measurement
Non-equal accuracy measurement means that use pressure sensors with different accuracy or different measurement methods to repeat the measurement for the same measured value. Perhaps do a repeated measurement when the environmental condition are very different.

IV. According to pressure change

• Static measurement
During the measurement, the measured quality is considered as consistent. This measurement is called static measurement. Static measurement do not need to consider the influence of time factors on the measurement results.
• Dynamic measurement
If the measured quality is constantly changing over time during the measurement, this measurement is called dynamic measurement.

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