Emerson Process Management 5300 manual Analyzing the Measurement Signal, Distance, m

Reference Manual

00809-0100-4530, Rev BA July 2009

Rosemount 5300 Series

ANALYZING THE MEASUREMENT SIGNAL

Figure 7-1. The Echo Curve presents all visible echoes

Rosemount Radar Master (RRM) and other tools using enhanced EDDL has powerful functions for advanced troubleshooting. Using the Echo Curve plot function, an instant view of the tank signal is shown. Measurement problems can be solved by studying the position and amplitude of the different pulses.

Amplitude, mV

P2 Interface

P1 Surface

Probe End

Reference

Interface Threshold

Surface Threshold (ATC)

Probe End Threshold

Reference Threshold Full Tank Threshold

3.0 4.0 5.0 6.0

Distance, m

In a typical measurement situation, the following pulses appear in the diagram:

Reference. This pulse is caused by the transition between transmitter head and probe. It is used by the transmitter as a reference at level measurements. The pulse amplitude depends on the probe type and installation geometry.

Product surface. This pulse is caused by a reflection on the product surface.

Interface. This pulse is caused by reflection on the interface between an upper product and a bottom product with a relatively high dielectric constant. This pulse is shown when the transmitter is in Measurement Mode=Level & Interface.

Probe End. It is caused by reflection on the probe end. If the probe is grounded, the pulse will be positive.

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. 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.

The following amplitude thresholds are used for the Rosemount 5300 Series transmitter:

Reference Threshold - amplitude threshold for detection of the Reference pulse.

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