Siemens FST020, Function Manual, Page: 70 / 194

Setup
3.4 Inputs and outputs
FST020 Function manual
68
Function Manual, 09/2017, A5E42949526-AA
Example
● Pulse output configuration (channels 2 to 4)
–
Operation mode = Pulse output
– Process value = Mass flow
– Amount per pulse = 1 kg
– Pulse width = 1 ms
● Measured mass flow value = 10 kg/s (constant)
Result:
● Pulse repetition = 100 ms
● Output frequency = 10 pulses per second with a pulse width of 1 ms
● Remaining time between pulses is 99 ms
Note
Pulse width must be selected with the view that remaining time is always greater than pulse
width at the highest measured flow.
Frequency output
The frequency output function supplies a frequency (50% duty cycle) proportional to the
selected process value.
Frequency is calculated as follows:
Example
This example shows how to calculate the output frequency for any measured flowrate:
Frequency output configuration:
● Operation mode = Frequency output (Channel 2 to 4)
● Process value = Mass flow
● Direction = Positive
● Frequency value high = 12 kHz
● Frequency value low = 2 kHz
● Upper range value = 15 kg/s
● Lower range value = 5 kg/s