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1, the transmitter to measure what kind of pressure to determine the maximum value of the measured pressure in the system, in general, need to select a transmitter with a pressure range of about 1.5 times greater than the maximum. This is mainly because in many systems, especially in water pressure measurement and processing, there are peaks and continuous irregular up and down fluctuations. This instantaneous peak can destroy the pressure sensor. Constantly high pressure values ​​or slightly beyond the transmitter's calibration maximum shorten the life of the sensor, which also degrades accuracy. Then a buffer can be used to reduce the pressure burr, 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 media viscous liquids and mud will plug the pressure interface? Solvent or corrosive substances will not damage the materials in the transmitter that are in direct contact with these media. These factors will determine whether to select the direct isolation membrane and the material directly in contact with the medium.
3. How much precision the transmitter needs to determine 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.
4, the transmitter temperature range Usually a transmitter will be calibrated two temperature segments, one of the temperature range is the normal operating temperature, the other is the temperature compensation range, the normal operating temperature range refers to the transmitter in working condition The temperature range when it is not destroyed may not reach its application performance index when it exceeds the temperature compensation range.
The temperature compensation range is a typical range that is smaller than the operating temperature range. In this range, the working transmitter will surely reach its proper performance. Temperature changes affect its output in two ways. One is zero drift, and the other is 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, need to get what kind of output signal
mV, V, mA, and frequency output digital outputs. Selecting the output depends on a variety of factors, including the distance between the transmitter and the system controller or monitor, whether there is "noise" or other electronic interference, and whether an amplifier is required. Position of the amplifier and so on. The most economical and effective solution for transmitters with mA output for many OEMs with short distances between transmitters and controllers.
If you need to amplify the output signal, it is best to use a transmitter with built-in amplification. It is better to use mA output or frequency output for long-distance transmission or strong electronic interference signals.
If you want to select mA or frequency output in an environment with high RFI or EMI specifications, consider special protection or filters.
6. Select the type of excitation voltage output signal to determine how to select the excitation voltage. Many 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, the operating voltage determines whether a sensor with a regulator is used. When selecting the transmitter, the operating voltage and system cost must be comprehensively considered.
7. Is it necessary to have interchangeable transmitters to determine if the required transmitter can accommodate multiple use systems? This is generally important, especially for OEM products. Once the product is delivered to the customer, the cost of the customer's calibration is quite large. If the product has good interchangeability, then even changing the transmitter used will not affect the overall system performance.
8, the transmitter needs to maintain stability after overtime work Most of the transmitter will produce a "drift" after overwork, so it is necessary to understand the stability of the transmitter before purchase, this advance work can be reduced There will be troubles in the future.
9, the transmitter's package encapsulation of the transmitter, it is often easy to ignore it is the rack, but this will be exposed in the use of its shortcomings. When selecting the transmitter, it is necessary to consider 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 between the transmitter and other electronic devices needs short-distance connections? If you use long-distance connections, do you need to use a connector?
Selection of pressure transmitters
Pressure transmitter should be selected, the following points for reference