BASI BLD-457, Руководство пользователя

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User manual - METER BDL-457
47
Figure. 9.4 Example of user defined characteristic
9.2. 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 I
n
result calculation
Let the input mode = 4-20 mA. The normalized I
n
result is calculated accordingly to the
expression on page 43, 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.
Prąd wejściowy [mA]
0
4 8 12 16 20
Y (PH)
0 0 , 2
35 0 ,
5 , 0 7 , 0
1
9 , 0
Y (PL)
X = „20.0.”
X = „35.0.”
X (PL) = „50.0.”
X (PH) = „70.0.”
X = „90.0.”
X = „100.0.”
Input current [mA]
Normalized measurement I
n
(for 0-20 mA range)
elements characteristic 5-