Siemens S7-300 - Page 275

Analog modules
9.3 SM 336; F-AI 6 x 0/4 ... 20 mA HART
Fail-safe signal modules
Installation and Operating Manual, 01/2010, A5E00085586-10
275
"Tolerance window %, relative" parameter
The tolerance window is calculated as a percentage of the smoothed process value that
represents the MIN or MAX value (depending on the parameter assignment of the standard
value) in this instant.
You can calculate the relative tolerance window using the following formula:
7
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Calculate the maximum deviation of the current using the following formula:
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With
● I
EW
= Process standard value (min./max.)
● I
MA
= 0 mA for measuring range 0 ... 20 mA
● I
MA
= 4 mA for measuring range 4 ... 20 mA
● T = Tolerance, in %
● ΔI
rel
= Maximum deviation of current (+/-)
You can assign a value of 0.2 to 20% for the "Tolerance window %, relative" parameter for
each channel pair.
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Figure 9-42 Relative deviation in % of the nominal range for measuring range 0 to 20 mA or 4 to 20 mA