Emerson Process Management 5300 manual Reference Threshold, Probe End Threshold

Reference Manual

00809-0100-4530, Rev BA July 2009

Rosemount 5300 Series

Reference Threshold

Figure C-7. Example of how to specify the Full Tank Threshold

Amplitude threshold for detection of the Reference pulse.

Probe End Threshold

If the Probe End Projection function is used (see “Dielectric Constant Settings” on page C-14), this threshold may need to be adjusted to make sure that the probe end pulse is properly detected.

Full Tank Threshold Offset

The Full Tank threshold is related to the Reference Threshold, and can be used for detecting that the tank is full. The given offset value determines the gap between the Reference threshold and the Full Tank threshold. The transmitter considers the tank full when the amplitude of the Reference Peak has dropped to a value between the two threshold values.

If the amplitude of the Reference peak is below the Full Tank Threshold (negative amplitude of the Reference peak), the tank is not considered full.

The Full Tank Threshold Offset should normally be set so that the Full Tank Threshold coincides with an amplitude value equal to 90% of the Reference Echo peak amplitude when the tank is not full.

Example

In the example below, the following assumptions are made (note the negative sign):

Reference Echo peak amplitude = -2000 mV Reference Threshold = -1000 mV

The target position for the Full Tank Threshold is at 10% below the Reference Echo peak amplitude. In this example, it means that the Full Tank Threshold should be located at 10% below the Reference peak at -2000 mV:

-2000 mV - (-200 mV)= -1800 mV

Since the Full Tank Threshold refers to the Reference Threshold, the resulting offset value has to be expressed in terms of the distance to the Reference Threshold:

Full Tank Threshold Offset = -1000 mV - (-1800 mV) = +800 mV.

Amplitude (mV)

Offset=+800 mV

- 10%

Reference Peak=-2000 mV

Interface Threshold

Surface Threshold

Reference Threshold

Full Tank Threshold

Distance (m)

3.0 4.0 5.0

By default, this value is 0 (function is not used). This is because highly contaminated or condensed tank-seals, and turbulent or boiling surfaces, which can cause splashing, may cause function to be triggered.

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