D
3-
-0
2D
A
2-
C
ha
nn
el
A
na
lo
g
O
ut
pu
t
6--8
D3--02DA 2-Channel Analog Output
Writing the Control Program
As mentioned earlier, you can update either channel or both channels during the
same scan. Since the module does not have any channel select bits, you just simply
determine the location of the data word and send the data word to the output module
whenever you need to update the data.
1
1
0
D3--02DA
R 011
MSB
LSB
R 001
MSB
LSB
0
1
0
R 002, R012
R 000, R010
1
1
7
8pt
Relay
8pt
Output
16pt
Input
16pt
(Analog)
2ch
Input
8pt
Output
050
--
057
040
--
047
030
--
037
020
027
--
120
127
000
007
--
100
107
010
017
--
110
117
0
1
7
Channel 1
Channel 2
Your program has to calculate the digital
value to send to the analog module.
There are many ways to do this, but most
all applications are understood more
easily if you use measurements in
engineering units. This is accomplished
by using the conversion formula shown.
You may have to make adjustments to
the formula depending on the scale you
choose for the engineering units.
A
=
256
U
H
-
L
A = Analog value (0 -- 255)
U = Engineering Units
H = high limit of the Engineering
unit range
L = low limit of the Engineering
unit range
The following example shows how you would use Engineering Units to obtain the
digital value to represent pressure (PSI) from 0 to 100. This example assumes you
want to obtain a pressure of 42 PSI, which is slightly less than half scale.
A
=
256
U
H
-
L
A
=
107.5 (or 108)
A
=
256
42
100
-
0
Identifying the
Data Locations
Calculating the
Digital Value
