Oval EX DELTA II, Инструкция по эксплуатации

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D-583-2N-E
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Fig. 9.3
9.2 Trigger Level
Trigger level (pulse generation sensitivity) determines
the peak value of amplified vortex signal above
which signal-to-pulse conversion takes place. It
follows that trigger level adjustment allows flow
sensitivity adjustment. With increasing TLV
pot position (clockwise rotation), flow sensitivity
decreases; with decreasing it (counterclockwise
rotation) increases flow sensitivity.
If measurement is made near the minimum flowrate
and resultant signal output is too small, adjust TLV
pot to a smaller position. An important precaution to
remember: setting TLV pot to an extremely small
position can lead to erratic pulse generation at zero
flow due to noises caused by pipeline oscillation or
other external disturbances.
TLV Potentiometer
(AMPLIFIER BOARD A)
ADJUSTABLE
RANGE
350mVp-p 80mVp-p
160mVp-p
(FACTORY
SET)
Trigger Level Potentiometer
Amplifier Board A:
TLV
Erratic pulse generation attributable to noises of pipeline oscillation, pulsating flows, etc. at meter shutoff can
be solved effectively by increasing TLV pot position.
The trigger level is factory adjusted to 60mV p-p before shipment.
(1) With increasing trigger level, the flow sensitivity decreases relative to that ratio of trigger level (sensitivity
ratio).
Example: When a trigger level 60mV p-p is increased to 350mV p-p, the resultant sensitivity declines by
a factor 60/350 ≒ /2.2 (sensitivity ratio).
(2) When sensitivity is changed, the resultant minimum flowrate (measurable lower bound flowrate) is
approximately the standard minimum flowrate multiplied by
1/(Sensitivity ratio)
.
Example: When a trigger level 60mV p-p is increased to 350mV p-p, the reultant minimum flowrate
becomes approximately
350 / 160 ≒
1.48 times the minimum flowrate.