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Re: Device Malfunction Bit

Message posted by Romilly ( : 80.229.220.91) on 09 December 2011 at 11:13:47.

in reply to: Device Malfunction Bit posted by Stephan Bhl on 05 December 2011 at 13:33:18.

Well, I would regard these two statements as the same. In any such detected situation where the measurment is not reliable, both these indicators would be set. Status bit 7 would be read by any host using HART, while the analogue output 'device malfunction' value would be noticed, and responded to, by any controller using the analogue value (or by an alarm relay set to trip at this value).

Can you think of a case where this would not be desirable?

(NAMUR recommendation NE43 advises the use of out-of-range analogue current values, beyond the normal over-range margins, to indicate a fault. See also www.romilly.co.uk/hartvars.htm and /namur.htm )




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