F
3-
-0
8A
D
8-
C
ha
nn
el
A
na
lo
g
In
pu
t
4--8
F3--08AD 8-Channel Analog Input
The remaining twelve bits represent the
analog data in binary format.
Bit
Value
Bit
Value
0 (LSB)
1
6
64
1
2
7
128
2
4
8
256
3
8
9
512
4
16
10
1024
5
32
11
2048
1
1
7
R001
MSB
LSB
0
1
0
1
1
6
1
1
5
1
1
4
1
1
3
1
1
2
1
1
1
1
1
0
0
1
7
0
1
6
0
1
5
0
1
4
0
1
3
0
1
2
0
1
1
-- data bits
R011
Since the module has 12-bit resolution,
the analog signal is converted into 4096
“pieces” ranging from 0 -- 4095 (2
12
). For
example, with a 4 -- 20 mA scale, a 4 mA
signal would be 0, and a 20 mA signal
would be 4095. This is equivalent to a
binary value of 0000 0000 0000 to
1111 1111 1111, or 000 to FFF
hexadecimal. The following diagram
shows how this relates to each signal
range.
Each “piece” can also be expressed in
terms of the signal level by using the
equation shown. The following table
shows the smallest signal levels that will
result in a change in the data value for
each signal range.
20mA
4mA
0
4095
4 -- 20mA
Resolution
=
H
-
L
4095
H = high limit of the signal range
L = low limit of the signal range
Range
Highest Signal
Lowest Signal
Smallest Change
4 to 20mA
20mA
4mA
3.91
µ
A
Now that you understand how the module and CPU work together to gather and
store the information, you’re ready to write the control program.
Analog Data Bits
