On 2018-08-08 14:48:54
How to choose a suitable pressure transmitter
The pressure transmitter has the advantages of reliable operation, stable performance, convenient installation and use, small volume, light weight, high performance price ratio, and can be widely used in various positive and negative pressure measurement. There are many kinds of pressure transmitters. You can choose a suitable pressure transmitter according to pressure medium, transmitter accuracy, what pressure to measure, output signal, excitation voltage, and other factors.
1. Type of pressure medium: viscous liquid and mud will block the pressure interface, and solvent or corrosive substances will not damage the materials in direct contact with these mediums in the transmitter. The above factors will determine whether to choose the isolation membrane and the material directly in contact with the medium.
2. Selection of transmitter accuracy: the accuracy is determined by nonlinearity, hysteresis, non repeatability, temperature, zero offset scale and temperature influence. But mainly by the non-linear, hysteresis, non repeatability, the higher the accuracy, the higher the price.
3. Selection of the pressure to be measured by the transmitter: first determine the Zui value of the pressure to be measured in the system. Generally speaking, it is necessary to select a transmitter with a pressure range about 1.5 times larger than the Zui value. This is mainly because in many systems, especially in water pressure measurement and processing, there are peaks and continuous irregular fluctuations, which can destroy the pressure sensor. Continuous high pressure value or a little more than the calibrated Zui value of the transmitter will shorten the life of the sensor, which will also reduce the accuracy. So a buffer can be used to reduce the pressure burr, but this will reduce the response speed of the sensor. Therefore, the pressure range, accuracy and stability should be fully considered when selecting the transmitter.
4. Selection of transmitter output signal: MV, V, Ma and frequency output digital output. The selection of output depends on a variety of factors, including the distance between the transmitter and system controller or display, the presence of "noise" or other electronic interference signals, the need for amplifiers, the position of amplifiers, etc. For many OEM equipment with short distance between transmitter and controller, using the transmitter Zui with Ma output is an economic and effective solution.
5. Selection of temperature range of transmitter: generally, one transmitter will calibrate two temperature ranges, one of which is the normal working temperature, the other is the temperature compensation range. The normal working temperature range refers to the temperature range when the transmitter is not damaged in the working state, and may not reach the performance index of its application when exceeding the temperature compensation range. The temperature compensation range is a typical range smaller than the working temperature range. Working in this range, the transmitter will certainly achieve its due performance. Temperature change affects its output from two aspects, one is zero drift, the other is full scale output. For example, + / - x% / ℃ of full scale, + / - x% / ℃ of reading, + / - x% of full scale when exceeding the temperature range, + / - x% of reading when within the temperature compensation range. Without these parameters, it will lead to uncertainty in use. The change of transmitter output to degree is caused by pressure change or temperature change. Temperature effects are a complex part of Zui when it comes to understanding how to use a transmitter. If the output signal needs to be amplified, Zui is better to use a transmitter with built-in amplification. For long-distance transmission or strong electronic interference signal Zui, Ma level output or frequency output is preferred. In the environment with high RFI or EMI index, special protection or filter should be considered in addition to Ma or frequency output.
6. Selection of excitation voltage: the type of output signal determines the selection of excitation voltage. Many transmitters have built-in voltage regulators, so their power supply voltage range is large. Some transmitters are quantitative configuration and need a stable working voltage. Therefore, the working voltage determines whether to use the sensor with regulator. When selecting the transmitter, the working voltage and system cost should be considered comprehensively.
7. Choice of interchangeability: determine whether the required transmitter can adapt to multiple use systems. Generally speaking, this is very important, especially for OEM products. Once the product is delivered to the customer, the cost of calibration by the customer is considerable. If the product has good interchangeability, the effect of the whole system will not be affected even if the transmitter used is changed.
8. Selection of transmitter package: it is easy to ignore the rack of transmitter package. However, this point will gradually expose its disadvantages in later use. When purchasing the transmitter, it is necessary to consider the working environment, humidity and installation of the transmitter in the future, and whether there will be strong impact or vibration.
9. The pressure transmitter needs to maintain stability after overtime operation: most transmitters will produce "drift" after overwork, so it is necessary to understand the stability of the transmitter before purchase, and this pre work can reduce all kinds of troubles in future use.