needed. But if the transmitter still does not track for example the product surface, it may
be necessary to manually adjust the thresholds.
Figure 7-12: Threshold Principle
A. The echo peak is below the threshold (dotted line) and is suppressed by the device.
B. This echo peak is interpreted as the product surface, since it is the first peak closest to
device that is above the surface threshold.
C. Threshold
D. Amplitude
E. Distance
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.
(6)
Surface threshold
Threshold to filter out noise in the echo curve for detection of the Surface. 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.
Interface threshold
Threshold to filter out noise in the echo curve for detection of the Interface. The first echo
peak after the surface echo that crosses and is above the Interface Threshold is the
interface echo.
(6) The reference threshold has no impact on the large coaxial probes since an internal reference point is used for those
probes.
Service and troubleshooting Reference Manual
April 2019 00809-0100-4530
200 Rosemount 5300 Level Transmitter
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