Explanation of explosion protection type: Ex dia IIC
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Explosion protection rating: NEPSI Ex dia IIC. I’m not sure what “dia” means
It’s E*a IIC or Ex d IIC; I’ve never seen the notation Ex dia IIC!
The original poster indeed made a mistake; it should be E*a IICT N (where N can be 1–6, indicating an intrinsically safe instrument) or Ex dII CT N (where N can be 1–6, indicating an explosion-proof instrument).
Yes, it was a mistake; EX de has connected letters, while dia has not been seen like that
Actually, d and ia should be written separately for explosion-proof and intrinsically safe types; this is a rather special case
Ex dia IIC is a dual explosion protection mark: d indicates that the main chamber has explosion protection, while ia denotes that the device itself is of intrinsically safe class ia.
A common explosion-proof design used in instruments is that for devices such as electromagnetic flowmeters and weighing modules, which require a high amount of energy and cannot be designed to be intrinsically safe, the transmitter is made explosion-proof while the sensor is designed to be intrinsically safe, thereby creating a hybrid explosion-proof/intrinsically safe design.