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The
Main threshold is defined by
“1.”, “2.”, “3.”
•
Adjustment is only permitted in justified cases: e.g.: elevated baseline, signal level, strong noise conditions close to the level transmitter!
•
Signals in the area below the two extremes and below the line are not selected.
•
The main threshold line can be changed in the Echo diagram by clicking Threshold settings / Threshold edit enabled in the pop-up context menu after
pressing the right mouse button.
•
Drag the dots on the graph with the left mouse button; the start, center, and end point have to be set to detect the minor noises in the waveform.
The peak of the level echo must be above it at all distances. It must be below the baseline of the signal and the noise.
Four Threshold masks are intended to mask larger-amplitude or infrequent protruding interferences. An example of this is the dot marked
“
4".”
in the figure.
•
Threshold extensions can also be modified on the Echo chart by clicking Threshold settings / Threshold edit enabled in the pop-up context menu after
pressing the right mouse button.
•
In the right-click context menu, you can add a new threshold line addition by clicking Threshold settings / Add Threshold mask point. Where the mouse
pointer is on the echo diagram.
•
It can be deleted with the Threshold settings / Del current Threshold mask point in the context menu by right-clicking on any of its points.
•
The middle of the three points can be moved
to the desired location by grabbing them with the left mouse button. It is advisable to leave at least 25 “ADC
values” at the top of the fault
, but not too much. As soon as the level reaches the interference signal, the amplitude of the level and the amplitude of the
interference signal add up, the threshold line addition must be lower to determine the distance.
•
The width of the threshold line completion can be adjusted by grasping its extreme points in a similar manner. -The width of the peaks usually fluctuates
less than their height, however, it is recommended to leave a little on them as well.
o
Deposits may form on the probe. the propagation speed of the radar signal in them slows down. Thus, over time, the distance shifts. Adding a
threshold line positioned wider and wider may alleviated the problem. Although the peak of the level is selected, its distance will not be
corrected.
Further points in the diagram:
“5.”: radar
reference signal (transmitter signal or ping).
“6.”:
flange impulse (does not occur with a coaxial probe).
“7.”: reflection from the probe’s end of weight
.
“8.”:
the echo peak of the level.
5.3.4.
Typical Signal Forms
The following diagrams show typical waveforms recorded in Echo diagram mode.
Emitted pulse
Flange
Level signal
Emitted pulse
Flange
Level signal
Emitted pulse
Level signal
Emitted pulse
Level signal
Rod or cable probe in stage 1 gain
Rod or cable probe in stage 2 gain
Coaxial probe in stage 1 gain
Coaxial probe in stage 2 gain
There is no flange reflection in the coaxial probe diagram because the mechanical design does not cause an impedance change along the probe at the flange.
The amplitude of the signal reflected from the surface of the measured substance increases as the level increases and decreases as the level decreases.
Note for the measurement of solids:
for most solids measurements, the measurement is made at a gain factor of 3 (except for powders and granules with a high
dielectric constant (
r
), such as carbon dust).
If there are difficulties with the level measurement between the device's gain factor 1 and 3 at a certain point in the level measurement, there is usually some interfering
object (protruding part, etc.) in the tank in the path of the electromagnetic measuring pulse. Thus, the device gives a false level value when it detects the largest signal
reflected there.
