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D-546-9-E
9. FLOW SENSITIVITY ADJUSTMENT PROCEDURE
Flow sensitivity is accurately adjusted over the
specified flow range before the meter leaves the
factory.
If no output appears at the minimum flowrate
presumably due to your specific operating
conditions (disturbance from external interference,
for example), readjust the sensitivity (trigger level).
The same sensitivity readjustment is also required in
cases where the receiving instrument registers
erratic counts at meter shutoff due to noises caused
by pipeline oscillation, etc. after sensor replacement.
9.1 Amplifier Gain
Amplifier gain (amplification) is adjusted to the
sensor used. Do not attempt to readjust it except
when the sensor has been replaced.
Amplifier gain is adjustable with AMP poten-
tiometer on the amplifier board A.
Monitor the vortex waveform following amplification
on the oscilloscope and adjust such that the peak
value of vortex waveform is 100mV p-p approx. at
the minimum flowrate.
Sensitivity Potentiometer
Vortex Waveform After Amplification
Amplifier Board A: AMP
Amplifier Board A： VTX （＋）－ 0V （－）
9.2 Trigger Level
When the peak value of amplified vortex waveform
exceeds a predetermined trigger level (threshold
value for producing a pulse signal), conversion into a
pulse takes place. Hence, trigger level adjusts flow
sensitivity: turning TLV pot clockwise decreases
flow sensitivity; turning it counterclockwise increases
flow sensitivity.
If it is desired to cover a measuring range close to the
low limit flowrate, or in an application where output
is low near the minimum flowrate, set TLV pot to a
lower position.
An important precaution to remember: setting
TLV pot too low can lead to erratic pulse
generation at zero flow due to noises caused by
pipeline oscillation or other external disturbances.
Trigger Level Potentiometer
Amplifier Board A: TLV
