DL205 Analog Manual, 7th Edition Rev. D
2-13
Chapter 2: F2-04AD-1, F2-04AD-1L, 4-Channel Analog Current Input
1
2
3
4
5
6
7
8
9
10
11
12
13
14
A
B
C
D
1
2
3
4
5
6
7
8
9
10
11
12
13
14
A
b
C
D
Active Channel Indicator Inputs
Two of the inputs are binary-encoded to indicate the
active channel (remember, the V-memory bits are
mapped directly to discrete inputs). The inputs are
automatically turned on and off to indicate the active
channel for each scan.
Scan X35
X34 Channel
N
Off
Off
1
N+1 Off
On 2
N+2 On
Off 3
N+3 On
Off 4
N+4 Off Off 1
Module Diagnostic Inputs
The last two inputs are used for module diagnostics.
Module Busy - The first diagnostic input (X36 in this
example) indicates a ”busy” condition. This input will
always be active on the first PLC scan, to tell the CPU
the analog data is not valid. After the first scan, the input
usually only comes on when extreme environmental
(electrical) noise problems are present.
NOTE:
When using the pointer method, the value placed into the V-memory location will be 8000 instead of the bit being
set.
The programming examples in the next section shows this input can be used. The wiring
guidelines shown earlier in this chapter provide steps that can help reduce noise problems.
Missing 24VDC - The last diagnostic input (X37 in this example) indicates that 24VDC has
not been applied to the card. For example, if the 24 VDC input power is missing or if the
terminal block is loose, the module will turn on this input point. The module also returns a
data value of zero to further indicate there is a problem.
The next section,
Writing the Control Program
, explains how these inputs can be used in a
program.
Module Resolution
Since the module has 12-bit resolution, the analog
signal is converted into 4096 counts ranging from 0 -
4095 (212). For example, a 4 mA signal would be 0 and
a 20 mA signal would be 4095. This is equivalent to a a
binary value of 0000 0000 0000 to 1111 1111 1111, or
000 to FFF 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.
MSB
LSB
X
2
0
X
3
5
X
3
4
= channel inputs
V40401
MSB
LSB
X
2
0
X
3
7
X
3
6
= diagnostic inputs
V40401
20mA
4mA
0
4095
4 -- 20mA
Resolution
=
H
−
L
4095
H = high limit of the signal range
L = low limit of the signal range
16mA / 4095 = 3.907uA per count
Summary of Contents for DL205
Page 1: ...DL205 Analog I O Manual Manual Number D2 ANLG M ...
Page 2: ...Notes ...
Page 6: ...Notes ...
