Avoid the pitfalls when choosing pressure transmitters

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Pressure transmitters are used to measure the level, density, and pressure of liquids, gases, or vapors, and they convert pressure signals into 4–20mA DC signals for output. They have the following advantages: 1. Pressure transmitters feature reliable operation and stable performance; 2. They utilize dedicated V/I integrated circuits, which result in few peripheral components, high reliability, easy maintenance, small size, light weight, and great convenience for installation and calibration. 　　3. Aluminum alloy die-cast casing with three-terminal isolation and an electrostatic spray paint coating for durability. 　　4.4-2mA DC two-wire signal transmission, with strong anti-interference capability and long transmission distance. 　　5. Three types of indicator heads – LED, LCD, and pointer – make on-site reading very convenient. It can be used to measure viscous, crystalline, and corrosive media. 　　6. High accuracy, high stability. Apart from the imported original sensors, which have been corrected using lasers, comprehensive compensation is provided for the temperature drift and non-linearity of the entire device within its operating temperature range. With the development of society, many industries are increasingly adopting electronic pressure gauges, also known as pressure transmitters. However, due to factors such as the working environment, the type of medium, and the temperature of the medium, these factors must be taken into consideration when selecting a pressure transmitter. Now I will discuss the considerations for choosing a pressure transmitter. First, the material in contact with the medium: We need to consider the medium that the pressure transmitter will measure. Generally, the material used for the parts of the pressure transmitter that come into contact with the medium is 316 stainless steel. If the medium does not corrode 316 stainless steel, then basically any pressure transmitter will be suitable for measuring the pressure of that medium. If the medium does corrode 316 stainless steel, then chemical sealing is necessary; this not only allows for the measurement of the medium’s pressure but also prevents the medium from coming into contact with the parts of the pressure transmitter that are in contact with it, thereby protecting the transmitter and extending its lifespan. Second, accuracy level: Every electronic measuring device has some degree of accuracy error. However, the accuracy levels specified by different standards vary. For example, in countries like China and the United States, the accuracy is defined as the range where the sensor exhibits the best linearity, that is, between 10% and 90% of the measurement range. In Europe, however, the accuracy is defined as the range where linearity is poorest, that is, between 0% and 10% as well as between 90% and 100% of the measurement range. If the accuracy specified in Europe is 1%, then in China it would be 0.5%. Third, measurement range: It is generally best for a sensor to have a maximum measurement range of 70% of its full scale. For instance, if we want to measure a pressure of 70 bar, we should choose a pressure transmitter with a range of 100 bar. Fourth, output signal: Due to various data acquisition requirements, there are many different output signals available for pressure transmitters on the market, including 4…20mA, 0…20mA, 0…10V, 0…5V, etc. The most commonly used signals are 4…20mA and 0…10V. Among these output signals, only 4…20mA is a two-wire system (the number of wires referred to here does not include ground or shield wires); all others are three-wire systems. Fifth, medium temperature: Since the signal from a pressure transmitter is converted through electronic circuits, the typical operating temperature range for such transmitters is from -30 to +100 degrees Celsius. If the temperature is too high, a condensation coil is usually used to cool the medium, which reduces the cost of having the manufacturer produce a pressure transmitter that can withstand high temperatures. Sixth, the medium being measured: If we are measuring relatively clean fluids, a standard pressure transmitter will suffice. If the medium is prone to crystallization or is viscous, an external diaphragm or chemical sealing is required to prevent the medium from blocking the pressure measurement ports. Seventh, other factors: After determining the above five parameters, we also need to consider the process connection interfaces of the pressure transmitter as well as its supply voltage. In special applications, explosion protection and protection ratings also need to be taken into account.