Automatic surface threshold
When this option is selected, the transmitter automatically sets the Surface threshold to a
constant value based on the configured Dielectric Constant of the product.
Note that by enabling the Automatic Surface threshold setting, the Amplitude Threshold
Curve (ATC) is replaced by a constant threshold value.
The Surface threshold can also be manually set by using the Set Threshold function (see
The configuration mode tab).
Example 1: Product surface peak not found
If the transmitter does not track the product surface correctly, it may be necessary to
adjust the threshold values. In Figure 7-18, the Surface Threshold is too high and as a result
the product level will not be detected. In a situation like this, the Surface Threshold has to
be lowered so that the surface peak is not filtered out.
Figure 7-18: Surface Threshold Is Too High
A. Amplitude
B. Distance
C. Surface Threshold is above the Product Surface peak. Surface Threshold= Amplitude
Threshold Curve (ATC)
If there are disturbing objects in the tank, the Surface Threshold must be carefully set to
avoid locking on the wrong amplitude peak. In Figure 7-19, the Surface Threshold is too
low, and as a result the transmitter has locked on a peak above the actual product surface.
A disturbance was interpreted as the product surface, since this was the first amplitude
peak closest to device that went above Surface Threshold. The actual product surface was
interpreted as the interface or the probe end.
Reference Manual Service and troubleshooting
00809-0100-4530 April 2019
Reference Manual 209
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