PDU–4xx–W
©
Dinel, s.r.o.
34
9 . Displayed values calculation
For simplicity of examples it's assumed that current input is selected, and all calculations are related
to this input. When voltage input is selected calculations are similar (be sure of particular ranges
and units). The first step to compute the result of measure is the calculation of the normalized result
(it means result of 0-1 range). To do it, the begin of the input range (0 mA for 0-20mA range, and
4mA for 4-20mA range) must be subtracted from measured value. Next, received result must be
divided by the width of the input range ( it means 20mA for 0-20mA range, and 16mA for 4-20mA
range). So normalized result can be expressed by expressions:
If measured value exceeds the nominal input range (0-20mA or 4-20mA), and do not exceed the
permissible input range, then received normalized In result exceeds 0-1 range, e.g. input range
4-20 mA, input current = 3 mA – the normalized result is equal -0,0625, and for input current = 22
mA, the normalized result is equal 1,125. In such cases presented expressions are still correct.
8.6. Over-current protection
The current input of the device is equipped with over-current protection circuit. This circuit protects
the standard resistor against damage. Maximum input current is set to 40mA (typical). When
temperature of the standard resistor falls, the protection circuit will turn on automatically, and the
device will measure the input current again. Due to thermal phenomenon in the standard resistor,
precision of the measurement may be lower until to the standard resistor temperature will falls to
the environment temperature.
9.1. Additional calculations (used conversion characteristic)
The manner of the additional computation of the displayed result depends on selected conversion
characteristic. All presented charts are connected with the input range 4 - 20 mA.
Linear characteristic
The normalized result is converted by fixed coefficients determined by
“Lo C”
and
“Hi C
” parameters
(when the normalized results is equal 0, then value
“Lo C”
is displayed, and when the normalized
results is equal 1, then value
“Hi C”
is displayed). Expression presented below shows the manner
of result calculation:
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
W
means the displayed value.
The value of the
“Lo C”
parameter can be higher than the value of
“Hi C”
parameter. In such
a case, for an increasing value of input current the displayed value decreases.
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
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 I
inp
. Means input current (in mA), and In – normalized result.
for 4 ÷ 20mA range
for 0 ÷ 20mA range
