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Register Value
Converted Decimal
Calculated Temperature
(Converted Decimal ÷ 20)
Two's Complement Value
Decimal Value
0000 0000 0000 0101
5
5
0.25
0000 0000 0000 0100
4
4
0.20
0000 0000 0000 0011
3
3
0.15
0000 0000 0000 0010
2
2
0.10
0000 0000 0000 0001
1
1
0.05
0000 0000 0000 0000
0
0
0
1111 1111 1111 1111
65535
-1
-0.05
1111 1111 1111 1110
65534
-2
-0.10
1111 1111 1111 1101
65533
-3
-0.15
1111 1111 1111 1100
65532
-4
-.20
1111 1111 1111 1011
65531
-5
-0.25
1111 1100 0001 1000
64536
-1000
-50
5.9.1 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 10 V
10 V
0 V
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 to 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 to 10 V output. The starting distance is 200 mm and the last distance will be 2000
mm (4 mA = 200 mm and 20 mA = 2000 mm). This defines the null as 200 and the span as 1800.
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