Figure. 10.4 Example of user defined characteristic
0
4
8
12
16
20
0
1
10.2. EXAMPLES OF CALCULATIONS
Example 1: Selection of the permissible input range (“4-20” mode)
If in
“4-20”
mode the user sets
“Lo r”
= 20,0% and
“Hi r”
= 10,0%, then permissible input currents range will
be equal: 3,2 mA ÷ 22 mA. Lower border of the range is the result of calculations: 4 mA - 4 mA × 20%, and the
higher : 20 mA + 20 mA × 10%.
Example 2: The normalized In result calculation
Let the input mode = 4-20 mA. The normalized In result is calculated accordingly to the expression on page
40, so if I
in
= 10 mA then 10 mA - 4 mA = 6 mA, and this result should be divided by the width of input range
(16 mA). Finally the normalized result: I
n
= 6/16 = 0,375.
In case when input current exceeds nominal measurement range, calculations are similar. For example if
input current is equal 2,5 mA then I
n
= (2,5 - 4)/16
≅
-0,0938, and if input current is equal 20,5 mA then
I
n
= (20,5 - 4)/16
≅
1,0313.
Example 3: The linear characteristic
Let the input mode = 4-20 mA, and parameters
“Lo C”
and
“Hi C”
equal to -300 and 1200 respectively. The
calculations will be done for three different input currents from example 2.
41
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