3.3 SINGLE AND QUADRATURE INPUTS
In most industrial flowmetering applications, a frequency producing flowmeter
has only a single output.
However, in many custody transfer applications, it is a requirement that the
flowmeter has two outputs so that the integrity of the signal can be assured. This
usually requires a turbine meter to have two coils, or a positive displacement
meter to have two pulse units.
The Model 414Q can interface to flowmeters fitted with two sensors and
connections to the flowmeters are outlined in Section 6.1.
The quadrature input has two functions.
1 To detect a difference in the number of pulses from each input
during delivery.
The instrument will alarm if the pulse difference (since reset) exceeds
1 in 1000 pulses. When an alarm condition exists the totals will cease
counting and will freeze at the last total prior to the alarm.
On detection of the alarm condition, the alarm output on terminal 7
will go low (energise), the output relays will de-energise and the stop
LED will flash, indicating that the batch can be continued by pressing
the RUN key or aborted using the STOP key. The display will also
periodically flash the error message, ERR 13.
2 Bi-directional Flow.
The 414Q has the ability to detect forward and reverse flow. The
inputs must be connected with channel 1 being the 90° flow signal and
channel 2 being the 0° signal. For forward/reverse detection to
function correctly, there must be clear definition of the input signals.
18 Operation
Summary of Contents for 414Q
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