Design, Assembly and Service Manual
Page 31 of 44
Induction flow meter FMG600 series
Pulse outputs
In any of the pulse modes, an pulse will be generated as soon as a defined (preset) fluid volume passes
through the meter sensor. The impulse mode requires specification of the following
three parameters: pulse width “
t
U
“, minimum time gap between two successive impulses “
t
D
“ and fluid
volume per impulse “
V
”.
This mode provides for integration of the flow rate
values in time. As soon as a preset fluid volume V
passes through the meter, an impulse of width t
U
is
generated. After each impulse, a gap of at least t
D
follows. If, after elapsing of the t
D
period, fluid volume
V has not yet passed through the sensor, the output
remains inactive. If the volume passed is equal to or
greater than V, another impulse plus gap are
immediately generated. Should the preset volume V
pass before the end of the previous impulse, the non-
generated impulse will be stored in a accumulator with
the capacity of 255 impulses. Should the impulse
accumulator overflow, an error message will be
generated. To ensure correct functioning of the meter
impulse function, it is necessary to set the impulse
output parameters so that the expected impulse
frequency shall correspond to the impulse width and
gap length selected.
Pulse generation principle
It holds: maximum pulse frequency = 1 / ( t
U
+ t
D
)
The volume per impulse parameter can be set within the range of 0.001 to 1,000,000 liters. The pulse width
and gap length can be set at 10 to 2,550ms in steps of 10ms. The setting procedure consists
of selecting numbers from 1 to 255 on the meter display. Multiplied by 10, the figure shows the impulse width
or gap length in milliseconds.
From the above it follows that the maximum impulse frequency is 50 per sec.
Regarding the flow rate conditions (see below), impulses can be generated in three different modes. During
the tU periods, the output is closed.
Impulse frequency
Impulse frequency
Impulse frequency
Flow rate
Flow rate
Flow rate
Impulses
for
|Q|
Impulses
for
Q+
Impulses
for
Q-
