How to choose the correct sensor?

How to choose the correct sensor?

1, the transmitter to measure what kind of pressure: first determine the system to confirm the maximum measured pressure, in general, you need to select a transmitter with a pressure range of about 1.5 times greater than the maximum. This is mainly in many systems, especially in water pressure measurement and processing, high temperature disinfection, there are peaks and continuous irregular fluctuations, this momentary peak can damage the pressure sensor, continuous high pressure value or slightly beyond change The maximum value of the sender's calibration will shorten the life of the sensor, however, this will reduce the accuracy. Thus, a buffer can be used to reduce pressure burrs, but this will reduce the sensor's response speed. Therefore, when selecting the transmitter, it is necessary to fully consider the pressure range, accuracy and stability.
2. What kind of pressure medium: We have to consider the medium measured by the pressure transmitter. The viscous liquid and mud will plug the pressure interface. The solvent or corrosive substances will not be corroded. Material directly in contact with the media. These factors will determine whether to select the direct isolation membrane and the material directly in contact with the medium. The material of the contact pressure medium part of the general pressure transmitter is made of 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 you The medium is corrosive to 316 stainless steel. Then we must use a chemical seal. This not only can measure the pressure of the medium, but also can effectively prevent the medium from contacting the wetted part of the pressure transmitter, thus protecting the pressure from changing. The transmitter extends the life of the pressure transmitter.
3. How much precision the transmitter needs: decisive accuracy, nonlinearity, hysteresis, non-repeatability, temperature, zero-offset calibration, and temperature effects. But mainly by non-linear, hysteresis, non-repeating, the higher the precision, the higher the price. Each type of electronic meter will have an accuracy error, but because of the different levels of accuracy in each country, for example, the accuracy of national standards such as China and the United States is the best part of the sensor's linearity, which is what we usually do. The accuracy of the measurement range is between 10% and 90%; while the accuracy of the European standard is the worst part of the linearity, which is what we commonly refer to as 0 to 10% and 90% to 100% of the inverse of the measurement. Between the accuracy. If the European standard accuracy is 1%, the accuracy of the Chinese standard is 0.5%.
4, the transmitter temperature range: Usually a transmitter will calibrate two temperature ranges, the normal operating temperature range and temperature compensation range. The normal operation temperature range refers to the temperature range when the transmitter is not destroyed in the working state. When the temperature compensation range is exceeded, the application performance index may not be achieved. The temperature compensation range is a typical range that is smaller than the operating temperature range. Working within this range, the transmitter will definitely reach its proper performance. Temperature changes affect its output in two ways. One is zero drift; the other is affecting full-scale output. Eg +/-X%/°C of full scale, +/-X%/°C of reading, +/-X% of full scale when out of temperature range, +/-X% of reading when within temperature compensation range , without these parameters leads to uncertainty in use. The degree of change in the output of the transmitter is caused by a pressure change or a change in temperature. Temperature effects are the most complicated part of understanding how to use the transmitter.
5, what kind of output signal needs to be obtained: mV, V, mA and frequency output digital output, what kind 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. Do you need amplifiers, amplifier locations, etc. For many OEM devices that have a short distance between the transmitter and the controller, the most economical and effective solution is to use the mA output transmitter. If you need to amplify the output signal, it is best to use a transmitter with built-in amplification. For long-distance transmission or presence of strong electronic interference signals, it is best to use mA-level output or frequency output. In environments with high RFI or EMI specifications, special protection or filters must be considered in addition to the need to select mA or frequency output. (At present, due to the needs of various kinds of acquisition, 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 common ones are 4...20mA and 0...10V. Among the output signals I mentioned above, only 4...20mA is two-wire system. What we call output is a few-wire system. Does not include grounding or shielded wire, all other three-wire system)
6, choose what kind of excitation voltage: the type of output signal determines how to choose the excitation voltage. Many amplification transmitters have built-in voltage regulators, so their supply voltage range is large. Some transmitters are quantitatively configured and require a stable operating voltage. Therefore, a working voltage that can be obtained determines whether a sensor with a regulator is used. When selecting a transmitter, the operating voltage and the system cost must be comprehensively considered.
7. Do you need an interchangeable transmitter: Determine if the required transmitter can accommodate multiple systems. In general, this is important. Especially for OEM products. Once the product is delivered to the customer, the cost of the customer's calibration is considerable. If the product has good interchangeability, then even changing the transmitter used will not affect the overall system.
8, the transmitter needs to maintain stability after overtime work: Most of the transmitter will produce a "drift" after overtime work, it is necessary to understand the stability of the transmitter before purchase, this kind of pre-work can Reduce the troubles that will arise in future use.
9, the transmitter's package: The transmitter's package, especially it is often easy to ignore it is the rack, but this point in the future will gradually expose its shortcomings. The transmission of the optional transmitter must take into consideration the working environment, humidity, and how to install the transmitter in the future. Will there be strong impact or vibration.
10. What kind of connection is used between the transmitter and other electronic devices: Is it necessary to use a short-distance connection? If you use long-distance connections, do you need to use a connector?
11. Other: After confirming some of the above parameters, we must also confirm the process connection interface of your pressure transmitter and the supply voltage of the pressure transmitter; if you use it in special occasions, you must also consider the explosion protection and the protection class.

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