Rievtech EXM-12DC-DA-R-HMI, User Manual

Page: 282 / 443

282
Parameter PT
The periodic time PT can be provided by the actual value of another already-programmed function:
Analog comparator: Ax – Ay
Analog trigger: Ax
Analog amplifier: Ax
Analog multiplexer: AQ
Analog ramp: AQ
PI controller: AQ
Analog math: AQ
Data latching relay: AQ
Up/Down counter: Cnt
Parameter p (number of decimals)
Parameter p applies only to the display of the Ax value in a message text.
Description of the function
The function reads the value of the signal at the analog input Ax.
This value is multiplied by the value of parameter A (gain). Parameter B (offset) is added to the product, as
follows:
(Ax * Gain) + Offset = Actual value Ax
The function block calculates the proportion of the value Ax to the range. The block sets the digital output Q
high for the same proportion of the PT (periodic time) parameter, and sets Q low for the remainder of the time
period.
Examples with Timing Diagrams
The following examples show how the PWM instruction modulates a digital output signal from the analog
input value:
Example 1
Analog input value: 500 (range 0...1000)
Periodic time T: 4 seconds
The digital output of the PWM function is 2 seconds high, 2 seconds low, 2 seconds high, 2 seconds low and
continues in that pattern as long as parameter "En" = high.