Rosemount 5300 Series, Справочное руководство

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152
Reference Manual
00809-0100-4530, Rev DD
Service and Troubleshooting
May 2016
Service and Troubleshooting
Amplitude thresholds
Different amplitude thresholds are used to filter out unwanted signals and to pick up the
different pulses. The transmitter uses certain criteria to decide which type of pulse that is
detected.
For example, counting from the top of the tank, the first echo found above the Surface
Threshold is considered as the product surface, as illustrated in
Figure 7-2 . Other pulses
further away from the top, although above the Surface Threshold, are ignored.
When the surface echo is found, the next pulse below the product surface and with a signal
strength above the Interface Threshold, is considered as the Interface.
Figure 7-2. Threshold Principle
The following amplitude thresholds are used for the Rosemount 5300 Series Transmitter:
Reference Threshold - Threshold to filter out noise in the echo curve for detection of the
Reference peak. The reference peak is a strong negative echo very close to the device, see
Figure 7-1 on page 151 .
Surface Threshold - Amplitude threshold for detection of the Product level peak. Noise
below the threshold is suppressed. The first echo peak closest to the device that crosses and
is above the Surface Threshold is the surface echo.
The surface threshold is designed as a number of individually adjustable amplitude
threshold points, the
Amplitude Threshold Curve (ATC), see “Amplitude threshold curve” on
page 161 .
Interface Threshold - Threshold to filter out noise in the echo curve for detection of the
Interface level peak. The first echo peak after the surface echo that crosses and is above the
Interface Threshold is the interface echo peak.
Full Tank Threshold - Amplitude threshold that can be used to detect whether the probe is
fully submerged in the upper product or not.
Probe End Threshold - Threshold to filter out noise in the echo curve for detection of the
Probe End peak. The probe end peak is a fairly strong positive or negative echo (depending
on probe type) that is present at the probe end when tank is empty.
A
A
B
B
0
1000
2000
3000
4000
5000
1.0 2.0
3.0
-1000
-2000
The echo peak is below the
threshold (dotted line) and is
suppressed by the device.
Distance
Amplitud
e
This echo peak is interpreted
as the product surface, since
it is the first echo peak
closest to device that is
above the threshold.
Threshold