AutomationDirect DL205 - Writing the Control Program; Calculating the Digital Value

DL205 Analog Manual, 7th Edition Rev. D
11-12
Chapter 11: F2-08DA-2, 8-Channel Analog Voltage Output
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Writing the Control Program
Calculating the Digital Value
The control program must calculate
the digital value that is sent to the
analog output. Several methods can be
used to do this, but the best method
is to convert the values to engineering
units. This is accomplished by using
the formula shown.
Adjustments may need to be made to
the formula depending on the scale of
the engineering units.
Consider the following example which controls pressure from 0.0 – 99.9 PSI. Using the
formula will calculate the digital value to be sent to the analog output. The example shows the
conversion required to yield 49.4 PSI. The multiplier of 10 is because the decimal portion of
49.4 cannot be loaded in the program, so it is shifted right one decimal place to make a usable
value of 494.
Refer to the example on the next page to write the conversion program.
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A = U
4095
for 0–4095 output
format
H – L
A = Analog Value (0 – 4095)
U = Engineering Units
H = High limit of the engineering
unit range
L = Low limit of the engineering
unit range
A = 10U
4095
A = 494
4095
A–2023
10 (H–L) (1000–0)