Yokogawa digitalYEWFLO (DY) - Manual (Page 102)

TROUBLESHOOTING
IM 1F2B4-01-YIA
Page 97
6.4.7 Low-cut flowrate adjustment (parameter H07)
This filter is used to eliminate frequencies below the range of measurement. The adjustment value
becomes a multiplier on the default frequency to determine the actual low-cut frequency. The
adjustment range is 0.5 to 10.
First determine whether the noise frequency is below your minimum flow requirement:
1) Access parameter G02 (SPAN FREQUENCY) and record this value. Ratio your desired cut
off required flow rate (Qcut) to the flow rate corresponding to the span frequency (Qmax).
This ratio multiplied by the span frequency results in the frequency at your minimum flow
rate; i.e. (Qcut/Qmax)(G02)=Qcut frequency
2) Access parameter G01 (FREQUENCY) input and record this value. If this value is less than
the Qcut frequency value, proceed with the low-cut adjustment. If the value is higher, stop
here and follow the adjustment procedure for the “output is high for a known flow rate”
symptom.
3) Access parameter H07 (LOW-CUT FREQUENCY). Note the set value and increase that value
in steps of 0.5 until output is zero.
6.4.8 High-frequency filter adjustment (parameter H04)
Symptom: Output is high (beyond programmed span)
These software parameters filter out frequencies and eliminate such noise as sonic noise, some pump
noise and many situations where harmonic noise occurs. There are two parameter settings which affect
the high frequency filter.
First determine whether the noise frequency is above your maximum flow requirements:
1) Access parameter G02 (SPAN FREQUENCY) and record this value. Then access parameter
G01 (FREQUENCY) and record this value. If the G01 value is at least 1.2 times greater than
the G02 value, proceed with the high-cut frequency adjustment. Otherwise, take note of the
difference between the G01 and G02 values. If there is less than a 20% difference or G01
happens to be less than the G02 value, continuing with this adjustment may mean that readings
in the high end of the flow range may not be possible. If you wish to continue with the
adjustment, proceed to Step 2.
2) Access parameter H04 or H05 (either one is acceptable or both may be used in combination).
Increase the set value by one step and observe the output. If output is now zero, adjustment is
complete. If not, continue increasing value until output is zero.