Dynasonics Fusion Water Flow Meter - Manual (Page 15)

15
RATE PULSE OUTPUT
The FUSION is equipped with an open-collector transistor circuit
that outputs a pulse waveform that varies proportionally with
flow rate—from 0 Hz at zero flow rate to 1,000 Hz at full flow rate
(configuration entry FULL FLOW described in detail in the flow
meter configuration section of this manual). To ensure that
accurate readings are being recorded by the receiving
instrument, the FUSION and the receiving instrument must have
identical K-factor values programmed into them. Unlike standard
mechanical flow meters such as turbines, gear or nutating disk
meters, the K-factor of the FUSION meter can be changed by
modifying the FULL FLOW flow rate value. Please refer to the
equations on the following page for the Full Flow / K-factor
Calculation.
Two pulse output options are available with the FUSION:
 Turbine meter simulation—This option is utilized when a
receiving instrument is capable of interfacing directly with a
turbine flow meter’s magnetic pickup. The output is a
relatively low voltage AC signal whose amplitude swings
above and below the signal ground reference. The minimum
AC amplitude is approximately 500 mV peak-to-peak. To
activate the turbine output circuit, turn on SW1-2 and turn off
SW1-3.
 Square-wave (TTL) frequency—This option is utilized when a
receiving instrument requires that the pulse voltage level be
either of a higher potential and/or referenced to DC ground.
The output is a square-wave with a peak-to-peak voltage that
swings to the DC supply rail when the SW1-2 is ON or to an
alternate voltage level if SW1-2 is turned OFF and an external
pull-up resistor and power source are utilized.
IMPORTANT: The RATE PULSE and 4-20mA outputs cannot
be operated simultaneously. Select the desired output type
from the OUTPUT menu. Details of this selection are covered
in the Flow Meter Configuration section of this manual.