Emerson Process Management 5300 manual Surface Pulse not Found, Amplitude, mV

Reference Manual

00809-0100-4530, Rev BA July 2009

Rosemount 5300 Series

SURFACE PULSE NOT FOUND

Figure 7-2. Example 1: surface threshold is too high.

The amplitude thresholds are automatically adjusted to appropriate values to filter out noise and other non-valid measurements from the measurement signal.

The amplitude of the measurement signal, i.e. the amplitude of the signal that is reflected by the product surface, is related to the actual dielectric constant of the product. The amplitude threshold that is used by the transmitter is based on the parameter configuration of the current product dielectric constant (see “Basic Configuration Parameters” on page 5-4). Normally no other threshold adjustment is needed, but if the transmitter still does not track the product surface correctly, it may be necessary to adjust the threshold values.

Rosemount Radar Master (RRM) has a plot function showing the reflections along the probe (see “Using the Echo Curve Analyzer” on page 7-10).

If the amplitude threshold is too high, the product level will not be detected as illustrated in Figure 7-2.In a situation like this, the amplitude threshold has to be lowered so that the Surface peak is not filtered out.

Amplitude, mV

The Surface Threshold is above the Surface peak

3.05.0

Distance, m

Surface Threshold=

Amplitude Threshold

Curve (ATC)

Reference Threshold

If there are disturbing objects in the tank, the threshold must be carefully set to avoid locking on the wrong amplitude peak. In Figure 7-3,the transmitter has locked on a peak above the actual product surface, i.e. a disturbance was interpreted as the product surface, whereas the actual product surface was interpreted as the interface or the probe end.

7-5