Yokogawa digitalYEWFLO (DY) - Manual (Page 100)

TROUBLESHOOTING
IM 1F2B4-01-YIA
Page 95
to the axis of vibration.
• Check the gaskets to be sure they don’t protrude into the flow stream. If they do, trim them
as required or reinstall them.
• Be sure that wafer style meters are aligned properly using any alignment devices supplied
with the meter.
• If the meter is installed in non-conductive pipe, be sure the body is well grounded using an
external strap.
If a rem ote am plifier is used, confirm the following:
1) The interconnecting cable was factory term inated. If not properly connected, check the
term ination. Refer to "Cable" for m ore inform ation.
2) The rem ote electronics housing is well grounded.
3) Confirm the rem ote am plifier is correctly connected to the flowtube. If not properly connected,
an unexpected output can be generated by the am plifier.
If one or m ore of the sym ptom s m entioned above still exist after the piping checkout procedure,
perform the Noise Balance Adjustm ent procedure as follows:
6.4.4 Noise balance adjustment (parameter H01)
This adjustment balances the noise component in the output of the two piezoelectric crystals so that a
high signal to noise ratio can be obtained. This is basically a null-balance type adjustment; in other
words adjustment should be made throughout the range of possible values (-5 to +10) to determine the
lowest noise setting. This is not a simple min/max value setting.
Adjustment is made with a full pipe and no flow. If flow cannot be stopped, the best adjustment is
made at low flow rates (less than 1.6 f/s for liquids and 26 f/s for gas).
1) Connect an oscilloscope between test points TP2 and COM2 and observe the signal wave
form. Access parameter H01 and make adjustment throughout the range of possible values to
obtain the lowest noise component of the wave form. See Figure 6.4.1 below for wave form
examples.
Figure 6.4.1: TP2-COM2 Waveform