AutomationDirect DL205, Руководство пользователя

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DL205 Analog Manual, 7th Edition Rev. D
15-27
Chapter 15: F2-8AD4DA-1 8-Ch. In / 4-Ch. Out Analog Current Combination
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B
C
D
Module 16 Bit Output Resolution
Digital and Analog Output Data Value Conversion
Sometimes it is useful to be able to quickly convert between the signal levels and the digital
values. This is especially helpful during machine startup or troubleshooting. The table below
provides formulas to make this conversion easier.
A = A
min
+ [(D)(A
max
- A
min
) / (D
max
)]
D = (A - A
min
)(D
max
) / (A
max
- A
min
)
Output Value Comparisons: Analog, Digital, Engineering Units
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b
C
D
D = (10–4) 65535
16
D = (6)(4095.94)
D = 24576
Resolution Output Range If the digital value is known If the analog signal level is known.
16 bit
0–65535
4 – 20 mA
A = 4 + 16D
65535
D = (A – 4) 65535
16
20mA
4mA
0 65535
4 – 20 mA
Resolution
=
H
−
L
65535
H = high limit of the signal range
L = low limit of the signal range
16mA / 65535 = 0.244 A per count
16 Bit Output Resolution
μ
• A = analog current output value
• A
max
= maximum analog value
• A
min
= minimum analog value
• D = digital value from PLC CPU
• D
max
= maximum digital value
For example, if a 10mA analog output
signal is needed, the formula could be
used to determine the digital value (D) to
be stored in the V-memory location that
contains the output data.
Analog, Digital, and Engineering
Units Output Comparisons
Analog (mA)
Digital
16 Bit
E.U.
20 65535 1400
12 39321 700
10 32768 525
4 13107 0
The table to the right shows how the
output analog, digital, and engineering
unit values are related to each other. The
example is a measurement of pressure from
0.0–140.0 PSI, using a multiplier of 10 for
one implied decimal place.
Since the 4–20 mA output module has 16 bit reso-
lution, the analog signal is converted into 65536
(2
16
) counts ranging from 0 - 65535. For example,
a 4mA signal would be 0, and a 20mA signal would
be 65535. This is equivalent to a binary value of
0000 0000 0000 0000 – 1111 1111 1111 1111,
or 0000 – FFFF hexadecimal. The diagram shows
how this relates to the signal range.
Each count can also be expressed in terms of the
signal level by using the equation shown.