Yokogawa digitalYEWFLO (DY) - Manual (Page 101)

IM 1F2B4-01-YIA
Page 96
TROUBLESHOOTING
2) Connect a voltmeter at test points TP2 and COM2. Although the voltage read will be an RMS
value and not peak-to-peak, adjusting H01 to minimize this value will produce the lowest
noise component.
3) If an oscilloscope or voltmeter is not available, use parameters H20 and H21 to read the
amplitude of the voltage at test points TP2 and COM2. Set parameter H20 to EXECUTE and
then access parameter H21 which will display the peak to peak voltage. Adjust H01 until this
voltage is at its minimum value.
Note: Each time the H21 parameter is exited for adjustment of H01, it will be necessary to re-execute
parameter H20 in order to again read H21.)
If your symptom has not been corrected by this adjustment, perform the adjustment procedure
indicated for each symptom:
6.4.5 Noise judge (parameters B08, H06)
Symptom: Output is high for a known flow rate
This filter works to reject noise within the flow range of the meter by acting like a variable TLA
(Parameter H02). As density and/or velocity increase, the amplitude of the signal also increases. The
Noise Judge makes a judgment, based on the process conditions and the flowing velocity, as to
whether the amplitude is related to vortex formation or could only be the result of noise. The
amplitude cutoff value of this filter is set by parameter B08 (MINIMUM DENSITY).
1) Access parameter H06 (NOISE JUDGE) and be sure the filter is active.
2) Access parameter B08 (MINIMUM DENSITY) and change the value so it is twice the current
value.
3) Observe the meter output at various points throughout the flow range. If the output holds
constant or drops-out in spite of increasing flow, lower the value in B08 by 10% and then
repeat this step from the beginning. Continue this procedure until the “flat spot” or dropout
disappears.
6.4.6 TLA adjustment (parameter H02)
Symptom: Output occurs with no flow “or” output is unstable at low flow
The TLA adjustment (Trigger Level Adjustment) is used to set the minimum measurable flow or meter
threshold. The adjustment range is -1 to +2. Adjustment is performed with no flow.
1) Access parameter H02 (TLA). Record the set value and increase that value one step at a time
until the output is zero.
2) If the output is now zero, no further adjustment is required.
3) If this adjustment has not been successful, decrease the value of parameter H03 (GAIN) by
“1”, reset TLA to original setting and repeat Step 1 until output is zero.
4) If adjustment is still unsuccessful, proceed to Low-Cut Frequency adjustment.