Field device
A field device , FG for short . Field Device (FD) is a technical device in the field of automation technology that is directly related to a production process. In automation technology, " field " refers to the area outside of control cabinets or control rooms. Field devices can therefore be both actuators ( actuators , valves, etc.) and sensors ( measuring transducers ) in factory and process automation .
The field devices are then connected to a control and management system , usually via a fieldbus , or increasingly also via real-time Ethernet . The data is evaluated here and is then used for regulation, control and further processing. This includes B. also the visualization and display of the result (e.g. valve open / closed, pressure , flow rate , temperature ) for the staff.
Requirements and environmental conditions
In the case of field devices, high demands are placed on quality, robustness and availability. The use of field devices at ambient temperatures of −20 ° C to +85 ° C is not uncommon. The devices must also be designed for use in potentially explosive areas ( chemical , gas and oil industries ) ( explosion-proof ). Zone 0 is the highest safety level. Ex-safe means that even in the event of a short circuit, no ignitable spark may arise that could ignite an explosive gas mixture in the ambient air. This is achieved in particular by severely limiting the available power.
A failure or a malfunction of a field device in a process can result in extremely high costs, in particular in the case of a production standstill caused by it. Increased technical effort is made here for field devices in order to significantly reduce the risk of malfunctions or to be able to identify and report a defect independently. Functions are integrated into the field device with multiple redundancies, and measurement results are permanently monitored and verified internally. The safety requirements (SIL level) for the field device increase with its area of application. In nuclear power plants , for example, the highest safety level (SIL 4) applies. The probability of a failure here is ≥10 −9 to <10 −8 per hour.
The first attempts to operate the field devices wirelessly are already underway. The device then draws its energy from a battery . An energy-saving system is particularly important here, as a battery life of 5 years is assumed. Shorter maintenance intervals are uneconomical. Since the same extreme environmental conditions apply to the wireless field devices , the batteries are also subject to high requirements, some of which involve very complex chemical and technical processes in development and manufacture.