Spectrum 1734, Руководство пользователя

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4-12 Chapter 4: OE2CIH and HART
User’s Manual Pub. 0300272-03 Rev. B
The module is capable of reaching 21 mA for both ranges.
•
For 4 to 20 mA range, the low limit is 3 mA.
•
For 0 to 20 mA range, the low limit is 0 mA.
To determine what the user-defined High and Low Engineering values are, the
above formula is used to reverse scale the current to the user values. Use 21.0 as
the high end point; 0.0 or 3.0 as the low end point (depending on the range).
Then scale 20.0 to the High value and 0.0 or 3.0 to the low user value.
To allow the highest resolution for full end-to-end output limits use the following
values:
•
4 to 20 mA Range:
-
High Value = 29126
-
Low Value = -29127
The result is:
-
32767 = 21.0 mA
-
29126 = 20.0 mA
-
-29127 = 4.0 mA
-
-32768 = 3.0 mA
•
0 to 20 mA Range:
-
High Range = 29646
-
Low Range = -32768
High/Low Clamp Values
High/Low Clamp Values are signed 16-bit integers. Values may range from
32767 to -32768 and are based on user scaling (see above):
•
The outputs may not exceed these values.
•
The Low Clamp must be less than the High Clamp value.
•
If both values are equal (and one is non-zero), it is considered invalid.
Clamping values are clipped to each range limit as follows:
•
0 to 20 mA range: 0.0 mA–21.0 mA
•
4 to 20 mA range: 3.0 mA–21.0 mA
NOTE
It is expected that the AOP will check this limitation before sending the
configuration to the module.
When the output is set equal to or exceeding one of these values, the
corresponding High/Low Clamp Alarm bit is set.
Configuration Errors
The OE2CIH module ignores invalid configurations and retains its current
settings. The Module Status LED is set accordingly until a correct configuration
is given (see LED settings). The Module Status word will be set to 3.
Status Instance (100)
The Status Assembly consists of 4 bytes (two for Channel Status, two for Module