1. Analog input / output card: AI card: usually refers to the card that receives 4-20mA signal, Ao card: the card that outputs 4-20mA signal, RTD card: the thermal resistance signal, TC card: the thermocouple signal. Now many factories do not use RTD and TC cards. Generally, integrated temperature transmitter or temperature change safety barrier is used to convert the temperature signal into 4-20mA signal into AI card.
2. Digital input / output card: Di card: digital input card, do card: digital output card, which receives and outputs digital signals (or switching signals) respectively. In short, it is the on-off signal of 0 or 1.
3. PI pulse card, which receives pulse signals, is rarely used
4. Communication card: Modbus RTU communication card is often used, and the corresponding interface form is usually RS485 / 422. There are also RS232 interfaces, but they are not used much. Of course, there are Modbus TCP / IP card and RJ45 interface (the same as the network cable port on our computer). There is also PROFIBUS-DP card, which is used more and more in the past two years.
The above cards are commonly used in DCS. In fact, there are many cards in DCS, but they are not commonly used. For example, there were analog cards that received voltage signals (generally 1-5V) long ago, but now almost no one uses them.
As for smart cards, there is another saying that AI / AO cards can not only receive and send conventional 4-20mA signals, but also receive Hart signals. For example, AI cards can not only receive 4-20mA signals, but also read other parameters of field intelligent instruments.