Emerson Process Management 5300 manual Interface Pulse not Found

Rosemount 5300 Series

Reference Manual

00809-0100-4530, Rev BA July 2009

INTERFACE PULSE NOT FOUND

Figure 7-6. Echo Curve plot indicating that the amplitude threshold for the interface peak is too high.

In interface applications where the bottom product has a relatively low dielectric constant (<40), or if the signal is attenuated in the upper product, the amplitude of the reflected signal is relatively low and difficult for the transmitter to detect. In such cases, it may be possible to detect the reflected signal if the corresponding amplitude threshold is adjusted.

The Rosemount Radar Master (RRM) lets you view a waveform plot to analyze the measurement signal. The plot shows the signal and the thresholds used for the different amplitude peaks. By adjusting the Interface Threshold, it is possible to detect even weak interface signals.

Guidelines for amplitude threshold settings:

•The Interface Threshold should be approximately 50% of the interface signal amplitude.

•If possible, the Interface Threshold should be higher than the Surface Threshold.

You can use the RRM software or a 375 Field Communicator to change the amplitude thresholds. See “Using the Echo Curve Analyzer” on page 7-10for more information.

If the Lower Product Dielectric Constant is known, the corresponding configuration parameter can be changed as an alternative to adjusting the amplitude thresholds. See also “Dielectric Constant Settings” on page C-14.

Figure 7-6illustrates a situation where the Interface Threshold is too high. The signal amplitude peak at the interface between the upper and lower products is not detected in this case.

Amplitude, mV

The Interface Threshold is above the interface peak

3.0 5.0

Distance, m

Interface Threshold

Surface Threshold

Reference Threshold

By adjusting the Interface Threshold, the peak at the interface between the upper and lower products is detected as illustrated in Figure 7-7:

7-8