"Value used to substitute the data attribute instMag."
instMag is used to calculate the mag attribute (depending on the configuration attribute db). Suppose we have a vale range of 100. The last reported value is 50 and the deadband value is 10 per cent. The next report would be generated at 45 or 55. What happens when immediately after the value 50 has been reported the instMag value is set by substitution to a value of 80?
Will the new mag value 55 (+10 per cent) or 80? Is there a report with the new value 55 or 80?
Define that the calculation of the mag value depends either on the instMag and db value or on the substitution setting (of subMag).
Current text under mag:
The value of mag shall be updated to the current value of instMag when the value has changed according the configuration parameter db.
New text (proposal):
The value of mag shall be updated to the current value of instMag when the value has changed according the configuration parameter db or by setting the subMag greater than current value (1 + db/100) or less than current value (1-db/100).
I agree with Wolfgangs comment. However, I would not use a formula for the explanation. We had this discussion in the past, and we said, that the details of the deadband calculation are not standardised. I.e. you can use other calculations like e.g. an integral calculation.
I think the current text is clear in that sense: it says that an update will be to the CURRENT VALUE of InstMag (it does not say to the old value + deadband).
24 Apr 07
There is a misinterpretation when the deadband leads to an update of mag. It is not set to the old value + dead band, instead to the new value, if the value is bigger than the old value + dead band. Therefore in the example a substitution of the value 50 with 80 leads to a new value of 80. (80 > 55). By the way, due to changed quality normally always a report is sent....
Nevertheless, another text formulation might prohibit this kind of misunderstanding in the future, e.g. as follows:
The value of mag shall be updated to the current value of instMag when the instMag value is greater than current mag value*(1 + db/100) or less than current mag value*(1-db/100).