Siemens SITRANS FUP1010 Operating Instructions Manual page 127

Transit Time Adjustment: (Hot Key 3)
Observe the short vertical marker at the beginning of the receive signal in the Graph Screen
above. This line represents the position in time (Tn) where the flowmeter perceives the arrival
of the ultrasonic signal. There are actually two Tn markers, one for the upstream arrival time
and one for the downstream arrival time. For proper liquid sound velocity measurement these
Tn markers should be positioned near the beginning edge of the receive waveform envelope
(as shown), however, in cases of poor signal conditions it is possible for this measurement to
be off by several receive waveform cycles.
1. To adjust the Tn mark position press the <3> key on the keypad to bring up the [TnSet #]
2. Pressing the <+> or <-> keys will cause the Tn marker to move later or earlier, respectively.
3. To exit this mode, press the <0> key on the keypad.
Zero Crossover Adjustment: (Hot Key 4)
Observe the small "X" mark located on the zero crossing line near the middle of the receive
signal in the Graph Screen above. This "X" indicates the central crossover which the flowmeter
is using to measure the transit-time delta. This crossover will generally be close to the peak
of the Receive signal with at least one well formed (non-aberrated) receive cycle on each side
of the crossover.
1. If it appears that the placement of this crossover is unsatisfactory then it can be adjusted
2. To exit this mode, press the <0> key.
Envelope Threshold Adjustment: (Hot Key 5 & 6)
Pressing the <=> key causes the graph to toggle between the default signal waveform screen
and the signal envelope screen (see example below). This envelope screen can aid in the
diagnosis of Tn errors caused by unusual receive waveform distortion. Signal distortion is
sometimes caused by poor sensor selection or poor pipe wall conditions, which may result in
an incorrectly measured fluid sound velocity. To improve the automatic measurement of Tn,
FUP1010 IP67 Portable Flowmeter
Operating Instructions, 02/2010, A5E02951522A Revision 01
command.
As you adjust the Tn marker, both Tn and Vs (liquid sound velocity) will change accordingly.
by pressing the <4> key on the keypad, which will invoke the [ZCO Set #] command. The
crossover point can then be moved in either direction on the waveform using the plus <+>
or minus <-> keys. The change from the default value (in receive cycles) will appear in the
number to the right of the command.
Troubleshooting
10.3 Test Facilities Graph Screen
125