α
2 Simple Application Controllers
Function Blocks 6
6 - 29
6.14
Analog Output
The digital value on the word input pin is converted to a corresponding output voltage or
current on the specified channel on the AL2-2DA module. One of two output modes can be
selected, voltage or current output. In voltage output mode, digital values from 0 to 4000 are
mapped onto analog values from 0 to 10 volts. In the current voltage mode, digital values from
0 to 2000 are converted to a range of 4 to 20 mA. If a digital value less than the lower limit of 0
is input on the word input pin, the analog output will default to the lower limit of the analog
range (0 V or 4mA) for the specified output mode. If a digital value greater than the upper limit
is input, the analog output will default to the upper limit of the analog range (10V or 20mA) for
the specified output mode. The acceptable data types for the word input pin are constants,
analog inputs or FB output values. When more than one Analog Output FB is configured to use
the same channel, all FBs will be executed if their enable pins are active. The FB that is
executed last in the program will control the operation of the AL2-2DA board. The user cannot
know which FB will be executed last due to lack of knowledge of the controller’s processing
algorithms. Care should be taken to avoid situations in which two or more analog output
function blocks may conflict.
Table 6.15: Analog Output Function Block
Output Characteristics
Set up of the Analog Output Function Block directly from the
α
2
Series Controller
1 ) Allocate the input pin to be used for the function block.
Function
Set Item
Description
I
The digital value to be converted is entered on this word input pin.
M
Output Mode. If OFF voltage mode is selected, if ON current mode is
selected. If not connected voltage mode is selected (default).
E
D/A conversion is only effective when Enable is ON. An unconnected
enable input defaults to ON.
FB
The following two set item exist:
1) Digital word input to be converted by D/A conversion. Source can
be a constant, an analog input or the WORD output of a FB.
2) Select which channel (channel 1 or 2) to use on the 2DA board.
Output
1) Bit Output pin. When converting digital to analog, this pin is ON.
0 0 0
A O
I
P
Analog
output
Digital input
0
4000
10V
Digital input
0
2000
20mA
4mA
Analog
output
Digital input
10V
0
4000 4040
10.1V
Analog
output
Digital input
20mA
0
2000 2020
20.16mA
Analog
output
4mA
