In the field of industrial automation, the unification of signal standards is crucial. It is directly related to whether the entire industrial production system can operate efficiently and stably. In the early development of industrial automation, the issue of instrument signal standards was like a thorny problem, which seriously restricted the further development of the industry.
In the early days, there was no unified signal standard for instruments in the field of industrial automation. This is like being in a city without traffic rules, where vehicles drive randomly and in chaos. The signal standards of instruments and meters produced by different manufacturers vary widely.
This directly causes the design of many downstream equipment to become extremely complex. Take the design of displays as an example. Since they have to adapt to various signal standards, engineers need to spend a lot of time and energy adjusting circuits and optimizing programs. Not only that, the installation and maintenance costs of the equipment have also increased significantly. Imagine that maintenance personnel need to master the signal standards and debugging methods of many different devices. This is undoubtedly a huge challenge. Moreover, compatibility issues between different signal standards often lead to inability to communicate properly between devices, thus affecting the smooth progress of the entire production process.
Faced with this problem, many manufacturers have proposed their own solutions. Among the many suggestions, the main focus is on electrical signals. Various electrical signal standards have been proposed, and competition is fierce. Some manufacturers believe that a specific electrical signal range is more suitable for the needs of industrial automation, while other manufacturers insist that their own solutions have more advantages. Although this situation of a hundred flowers blooming has promoted technological innovation to a certain extent, it has also brought more chaos to the industry. Everyone is waiting for a widely recognized standard to emerge.
After a long period of precipitation and market testing, two widely accepted signal standards finally emerged. One is the pneumatic signal standard, selected as 20 - 100kPa.
Pneumatic signal standards: In some situations with extremely high explosion-proof requirements and harsh environments, pneumatic signals are still used. The common pneumatic signal standard range is 20100kPa. For example, in certain hazardous areas in petrochemical and other industries, pneumatic instruments use compressed air as the signal transmission medium to transmit measured values or control instructions in the form of changes in air pressure. The advantage of this signal standard is that it is intrinsically safe and does not produce dangerous factors such as electric sparks. However, the disadvantage is that the response speed is relatively slow and the signal transmission distance is limited, generally within tens of meters.
Pneumatic signals have unique advantages in some specific industrial scenarios. For example, in flammable and explosive environments, pneumatic signals are safer and more reliable. The other is the electric signal standard, 4-20mA has become the well-deserved gold standard.
4-20mA current signal: This is one of the most widely used analog signal standards in industrial fields. 4mA represents the lower limit of the signal, which usually corresponds to the zero point of the measured variable; 20mA represents the upper limit of the signal, which corresponds to the full range of the measured variable. For example, in temperature measurement, if the measurement range is 0°C100°C, 4mA may correspond to 0°C, and 20mA may correspond to 100°C. This signal standard has the advantages of strong anti-interference ability and long transmission distance. The general transmission distance can reach hundreds of meters or even thousands of meters, and can meet the signal transmission needs between different devices in most industrial sites.
The 4-20mA standard stands out mainly because it has many advantages. First, it has good anti-interference ability. In industrial production sites, there are various electromagnetic interferences. If the signal is easily interfered, it will lead to increased measurement and control errors and affect production quality. The 4-20mA signal can remain relatively stable in a complex electromagnetic environment, ensuring accurate data transmission.
Secondly, its transmission distance is relatively long. In large industrial enterprises, the distance between devices may be relatively long, and signals are easily attenuated during transmission. The strength and characteristics of the 4 - 20mA signal enable it to maintain good performance over long distances. In addition, this standard also enables fault diagnosis of signals. When the signal current is 0mA, it most likely indicates that there is a fault in the line, making it easier for maintenance personnel to find and solve the problem in time.
Although with the continuous development of science and technology, industrial automation is gradually transitioning to digitalization, and digital signals have shown great advantages in many aspects, analog signal transmitters are still widely used. This also fully reflects the strong vitality of the 4-20mA standard. Analog signal transmitters have the advantages of low cost, high reliability, and mature technology. In some industrial scenarios that are cost-sensitive and do not require particularly high signal accuracy, analog signal transmitters are still the first choice. Moreover, many existing industrial equipment are designed based on the 4-20mA standard. If all are to be replaced with digital equipment, not only will the cost be huge, but there will also be many problems such as technical transformation and personnel training.
The unification of instrument signal systems in industrial automation is an inevitable requirement for industry development. As an electric signal standard, 4-20mA stands out in the fierce competition and still plays an important role in current industrial production. As technology continues to advance, it may complement digital signals and jointly promote the development of industrial automation to a higher level.