Siemens SITRANS 7ME3500, Руководство по эксплуатации, Страница: 156 / 296

Troubleshooting
10.3 Test Facilities Graph Screen
FUE1010 IP65 NEMA 4X
154
Operating Instructions, 12/2014, A5E03086491-AC
The digitized receive signal can be expanded or contracted in the time domain by pressing
the <+> or <-> keys on the keypad. This allows you to see the entire contents of the receive
window, or zoom in to see greater detail. Pressing the <CLR> key once will automatically
center the receive signal on the screen. When expanding the Receive signal small vertical
"tick" marks will eventually appear. These marks represent the time at which the receive
signal is digitally sampled.
Correlated Plot
During conditions of flow, the actual transit time delta (difference) can be observed in the
displayed receive signal waveform when the [Correlated Plot] menu parameter is not
selected. To observe this time difference simply depress the <+> key (to see greater signal
detail) until the individual up and down receive signals are clearly discernible. To verify that
the flow meter signal processing algorithms are properly correlating the up and down stream
receive signals, select the [Correlated Plot] option from the display menu list.
Return to the graph screen and observe the relative position of the up and down waveforms.
In a properly correlated receive signal the two images should be nearly superimposed on top
of each other, even during high flow conditions. In the unlikely situation where the two
images appear to be offset by one or more receive cycles then the flow readings should be
considered questionable.
Command Modes
Although the flow meter signal processing algorithms are capable of accommodating a very
wide range of signal conditions, it may be desirable to override these default settings under
extremely difficult operating conditions. The following functions are available for this purpose.
Digital Damping Control: (Hot Key 1 and 2)
The Graph Screen includes the capability to access a set of command codes, which enable
a user to override a number of default meter settings. The most important parameter is the
digital damping control, which can be accessed by pressing number <1> or <2> on the
keypad while in the Signal Graph Screen mode.
The meter permits user modification of the digital averaging used by the signal processing
routines. In general, the default damping values selected by the flow meter will provide
optimal performance over a wide range of transit time applications. However, in extreme
cases of unstable flow, pulsating flow, low signal levels or high electronic noise it may be
necessary to override these default settings to permit uninterrupted and reliable flow
measurement.