I am not sure you can get Type A Differential Transmitters adding to the fact that they are generally SMART and/or a complex instruments. Simple components like relays, switches, valves, etc. are normally Type A. What is important in a Safety System is the SIL level you are trying to achieve. Both Type A and B can achieve SIL 4 in theory but I would be surprised a differential transmitter is specified within a SIL 4 Safety System. I have never known of one. Yokogawa offer Differential Transmitters that can achieve SIL 2 or 3 and it is the type we have used in our safety systems that have required SIL 2. The Yokogawa.web page has a number of reports explaining this and they are very useful. It is also covered in IEC61508 part 2 section 7.4. It also defines what Type A and Type B components (elements) are. There are tables for Type a and Type B components and the properties required to achieve the SIL levels. The properties being hardware failure tolerance and Safe failure fraction.

Hope this helps.

I am not sure you can get Type A Differential Transmitters adding to the fact that they are generally SMART and/or a complex instruments. Simple components like relays, switches, valves, etc. are normally Type A. What is important in a Safety System is the SIL level you are trying to achieve. Both Type A and B can achieve SIL 4 in theory but I would be surprised a differential transmitter is specified within a SIL 4 Safety System. I have never known of one. Yokogawa offer Differential Transmitters that can achieve SIL 2 or 3 and it is the type we have used in our safety systems that have required SIL 2. The Yokogawa.web page has a number of reports explaining this and they are very useful. It is also covered in IEC61508 part 2 section 7.4. It also defines what Type A and Type B components (elements) are. There are tables for Type a and Type B components and the properties required to achieve the SIL levels. The properties being hardware failure tolerance and Safe failure fraction.

Hope this helps.