Mapping Unit Types
Using signed or unsigned value types allows the user to generically map any input to any output. The signed and unsigned values read
the null and span parameters to create the linear translation between one scale and another. The output type is set to mA or V.
Output = (Fullscale/Span)(InputValue − Null) + Offset
Output Scale
Fullscale (range)
Offset
0 to 20 mA
20 mA
0 mA
4 to 20 mA
16 mA
4 mA
0 to 10V
10V
0V
Fullscale. Defined in the table; the output range.
Span. The total range of values mapped to the output.
Null. The starting point for the output scale.
Input Value. The value mapped to the output.
Offset. Defined in the table; the starting output value.
Example: Temperature Map
Map a temperature input from a Node to a 4–20 mA output. The starting temperature is −20°F and the last temperature will be 50°F (4
mA = −20°F, 20 mA = 50°F). This defines the null as −20°F and the span as 70.
With an input temperature value of −5°F, the output value will be:
Output = (Fullscale ÷ Span)(InValue − Null) + Offset
(Fullscale ÷ Span) = 16 ÷ 70 = 0.22857
(Value − Null ) = −5 − (−20) = 15
Offset = 4
Output = 0.22857 × 15 + 4 = 7.42 mA
Example: Distance Map
Map a distance input from a Node to a 0–10V output. The starting distance is 200mm and the last distance will be 2000mm (4 mA =
200mm, 20 mA = 2000mm). This defines the null as 200 and the span as 1800.
With an input distance reading of 1560mm, the output value will be:
Output = (Fullscale ÷ Span)(InValue − Null) + Offset
(Fullscale ÷ Span) = 10 ÷ 1800 = 0.00555
(Value − Null ) = 1560 − 200 = 1360
Offset = 0
Output = 0.00555 × 1360 + 0 = 7.54V
Alarm Conditions
The standard alarm conditions are as follows:
Unsigned Alarm = 0xFFFF
Signed Alarm = 0x7FFF
If special alarm conditions are needed, consult the factory for details.
SureCross Wireless I/O Network Manual
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