37
©
Dinel, s.r.o. PDU–4xx–W
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 In result calculation
Let the input mode = 4-20 mA. The normalized In result is calculated accordingly to the expression
on page 37, so if Iin = 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.
a). I
in
=10 mA a I
n
= 0,375
Accordingly to expression on page 38 for linear characteristic:
0,375 × [1200 -(- 300)] ≈ 562 and next, the “Lo C” value is added to the result , so the
displayed value:
W ≈ 562 + (-300) = 262
b). I
in
= 2,5 mA a I
n
= -0,0938
W ≈ -441
c). I
in
= 20,5 mA a I
n
= 1,0313
W ≈ 1247
Example 4: The square 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 there different input currents from example 2.
𝐼𝐼
𝑜𝑜𝑜𝑜𝑜𝑜
=
𝑊𝑊 − "𝑂𝑂𝑂𝑂𝑂𝑂𝑂𝑂"
"OUtH"-"OUtL"
× 16 𝑚𝑚𝑚𝑚 + 4 𝑚𝑚𝑚𝑚 𝑃𝑃𝑃𝑃𝑃𝑃 𝑃𝑃𝑃𝑃𝑟𝑟𝑟𝑟𝑟𝑟ℎ 4 − 20 𝑚𝑚𝑚𝑚
𝐼𝐼
𝑜𝑜𝑜𝑜𝑜𝑜
=
𝑊𝑊 − "𝑂𝑂𝑂𝑂𝑂𝑂𝑂𝑂"
"OUtH"-"OUtL"
× 20 𝑚𝑚𝑚𝑚 𝑃𝑃𝑃𝑃𝑃𝑃 𝑃𝑃𝑃𝑃𝑟𝑟𝑟𝑟𝑟𝑟ℎ 0 − 20 𝑚𝑚𝑚𝑚
𝐼𝐼
𝑛𝑛
=
𝐼𝐼
𝑖𝑖𝑛𝑛𝑝𝑝.
− 4
16
𝑃𝑃𝑃𝑃𝑃𝑃 𝑃𝑃𝑃𝑃𝑟𝑟𝑟𝑟𝑟𝑟ℎ 4 − 20 𝑚𝑚𝑚𝑚
𝐼𝐼
𝑛𝑛
=
𝐼𝐼
𝑖𝑖𝑛𝑛𝑝𝑝.
20
𝑃𝑃𝑃𝑃𝑃𝑃 𝑃𝑃𝑃𝑃𝑟𝑟𝑟𝑟𝑟𝑟ℎ 0 − 20 𝑚𝑚𝑚𝑚
𝑊𝑊 = 𝐼𝐼
𝑛𝑛
× (
"Hi C"
− "
Lo C"
) + "
Lo C"
𝑊𝑊 = 𝐼𝐼
𝑛𝑛
2
× (
"Hi C"
− "
Lo C"
) + "
Lo C"
𝑊𝑊 = √𝐼𝐼
𝑛𝑛
× (
"Hi C"
− "
Lo C"
) + "
Lo C"
𝑊𝑊 = (𝐼𝐼
𝑛𝑛
− 𝐼𝐼
𝑝𝑝
) ×
[𝑌𝑌 (𝑃𝑃𝑃𝑃) − 𝑌𝑌 (𝑃𝑃𝑂𝑂)]
[𝑋𝑋 (𝑃𝑃𝑃𝑃) − 𝑋𝑋 (𝑃𝑃𝑂𝑂)] × 100 + 𝑌𝑌 (𝑃𝑃𝑂𝑂)
𝑊𝑊 = (𝐼𝐼
𝑛𝑛
− 𝐼𝐼
𝑝𝑝
) ×
[𝑌𝑌 (𝑃𝑃𝑃𝑃) − 𝑌𝑌 (𝑃𝑃𝑂𝑂)]
[𝑋𝑋 (𝑃𝑃𝑃𝑃) − 𝑋𝑋 (𝑃𝑃𝑂𝑂)] × 100 + 𝑌𝑌
(𝑃𝑃𝑂𝑂)
= (0,375 − 0,3) ×
[80 − 30]
[40 − 30] × 100 + 30 ≅ 67
where Y(PH), X(PH), Y(PL), X(PL) mean values of X and Y coordinates of PH i PL points.
If the normalized result exceeds the user defined characteristic values, then specific utmost
segment, defined by two next points, is used for calculations. If characteristic from figure below is
used, and if In>1 then segment defined by points X(PL) =
“90.0.”
, X(PH) =
“100.0.”
will be used.
