How to choose the right sensor?

1. What kind of pressure should the transmitter measure: First determine the maximum value of the measured pressure in the system. Generally speaking, it is necessary to select a transmitter with a pressure range that is about 1.5 times larger than the maximum value. This is mainly because in many systems, especially in water pressure measurement and processing, high-temperature disinfection, there are peaks and continuous irregular up and down fluctuations. This instantaneous peak can damage the pressure sensor. Continuous high pressure values ​​or slightly exceeding the calibrated maximum value of the transmitter will shorten the life of the sensor. However, this will reduce the accuracy. Therefore, a buffer can be used to reduce the pressure burr, but this will reduce the response speed of the sensor. Therefore, when selecting a transmitter, the pressure range, accuracy and stability should be fully considered.
2. What kind of pressure medium: We need to consider the medium measured by the pressure transmitter. Viscous liquids and mud will block the pressure interface. Will solvents or corrosive substances corrode the materials in direct contact with these media in the transmitter? The above factors will determine whether to choose a direct isolation membrane and materials that are in direct contact with the medium. The material of the medium contact part of the general pressure transmitter is 316 stainless steel. If your medium is not corrosive to 316 stainless steel, then basically all pressure transmitters are suitable for your measurement of medium pressure. If your medium is corrosive to 316 stainless steel, then we have to use chemical seals, which can not only measure the pressure of the medium, but also effectively prevent the medium from contacting the liquid contact part of the pressure transmitter, thereby protecting the pressure transmitter and extending the life of the pressure transmitter.
3. How much accuracy does the transmitter need: The factors that determine the accuracy are nonlinearity, hysteresis, non-repeatability, temperature, zero offset scale, and temperature. But mainly due to nonlinearity, hysteresis, and non-repeatability, the higher the accuracy, the higher the price. Each electronic measuring instrument will have accuracy errors, but because the accuracy levels marked by different countries are different, for example, the accuracy of countries such as China and the United States is the best part of the sensor in terms of linearity, which is what we usually call the accuracy between 10% and 90% of the measurement range; while the accuracy of the European standard is the worst part of the linearity, which is what we usually call the accuracy between 0 to 10% and 90% to 100% of the measurement range. If the accuracy of the European standard is 1%, the accuracy of the Chinese standard is 0.5%.
4. Temperature range of the transmitter: Usually a transmitter will be calibrated with two temperature ranges, namely the normal operating temperature range and the temperature compensable range. The normal operating temperature range refers to the temperature range when the transmitter is not damaged in the working state. When it exceeds the temperature compensation range, it may not meet the performance indicators of its application. The temperature compensation range is a typical range smaller than the operating temperature range. Working within this range, the transmitter will definitely achieve its performance indicators. Temperature changes affect its output in two ways: one is zero drift; the other is the impact on the full-scale output. Such as: +/-X%/℃ of full scale, +/-X%/℃ of reading, +/-X% of full scale when out of temperature range, +/-X% of reading within temperature compensation range. Without these parameters, it will lead to uncertainty in use. Is the change in transmitter output caused by pressure change or temperature change? Temperature influence is the most complicated part of understanding how to use the transmitter.
5. What kind of output signal is needed: mV, V, mA and frequency output digital output. The choice of output depends on many factors, including the distance between the transmitter and the system controller or display, whether there is "noise" or other electronic interference signals. Whether an amplifier is needed, the location of the amplifier, etc. For many OEM devices with a short distance between the transmitter and the controller, the use of mA output transmitters is the most economical and effective solution. If the output signal needs to be amplified, it is best to use a transmitter with built-in amplification. For long-distance transmission or strong electronic interference signals, it is best to use mA-level output or frequency output. If you are in an environment with high RFI or EMI indicators, in addition to paying attention to the selection of mA or frequency output, you must also consider special protection or filters. (Currently, due to various acquisition needs, there are many kinds of output signals of pressure transmitters on the market, mainly 4...20mA, 0...20mA, 0...10V, 0...5V, etc., but the more commonly used ones are 4...20mA and 0...10V. Among the output signals I mentioned above, only 4...20mA is a two-wire system. The output we say does not include grounding or shielding wires, and the others are three-wire systems)
6. What kind of excitation voltage to choose: The type of output signal determines what kind of excitation voltage to choose. Many amplifier transmitters have built-in voltage regulators, so their power supply voltage range is large. Some transmitters are quantitatively configured and require a stable working voltage. Therefore, the working voltage that can be obtained determines whether to use a sensor with a regulator. When selecting a transmitter, the working voltage and system cost should be considered comprehensively.
7. Whether an interchangeable transmitter is required: Determine whether the required transmitter can adapt to multiple usage systems. Generally speaking, this is very important. Especially for OEM products. Once the product is delivered to the customer, the cost of calibration is considerable. If the product has good interchangeability, even if the transmitter is changed, it will not affect the effect of the entire system.
8. The transmitter needs to maintain stability after overtime work: Most transmitters will produce "drift" after overtime work, so it is necessary to understand the stability of the transmitter before purchase. This advance work can reduce the various troubles that will appear in future use.
9. Transmitter packaging: The packaging of the transmitter, especially its rack, is often easily overlooked, but this will gradually expose its shortcomings in future use. When purchasing a transmitter, you must consider the future working environment of the transmitter, the humidity, how to install the transmitter, whether there will be strong impact or vibration, etc. 10. What kind of connection
is used between the transmitter and other electronic equipment: Is a short-distance connection required? If a long-distance connection is used, is a connector required?
11. Others: After we confirm the above parameters, we also need to confirm the process connection interface of your pressure transmitter and the power supply voltage of the pressure transmitter; if it is used in special occasions, we also need to consider the explosion-proof and protection level.