ST300 SPIDER
28
As with any reflection meter, the precision depends on how correctly the velocity factor is set. Velocity
factor (VF) is a characteristic of conductive media that indicates how much more slowly an electromagnetic
wave travels in the medium than does light in vacuum, and depends on the specifics of the conductive
line, i.e., its cross-section and the electric properties of its materials (capacitance and inductivity per
length).
The velocity factor for a given cable can be found in special reference directories, cable
passport, or online. Please bear in mind that ST300 programming utilizes the reciprocal value
of the velocity factor!
For proper use of the reflection meter of ST300, any known devices must be disconnected from the
circuit, so the cable only is tested. Both ends of the cable must be accessible, and wires must not be
short-circuited at the far end. If the line in question has ramifications, it must be tested segment by
segment.
Fig.36
Fig.37
1 – current mode
2 – wire pair connected
3 – table line numbers
4 – distance to a detected defect (irregularity)
5 – level of the signal reflected from the defect (irregularity)
6 – table of measurements #2 (inactive)
7 – hotkey assignments
In Fig. 36:
1 – current mode
2 – wire pair connected
3 – table of measurements #1 (“Set 1”)
4 – table of measurements #2 (“Set 2”)
5 – hotkey assignments
Two tables are displayed on the screen. The user
can perform two consecutive measurement cycles and
compare the results. Grey highlighting of the table
fields means that the table is active (available for
measurements).
Using the two tables is convenient when testing
two pairs in one multiple-wire cable, or two different
twin-wire cables, or testing one pair of wires from the
opposite ends.
The reflection meter mode requires the connection
of two wires. If one of the pair is not connected, the wire
number will be shown as 0 (see 2, Fig. 36; both zeroes
indicate that neither is connected; measurements on
such a pair will not be taken, and the corresponding cell
in the active table will read, “No defects”. The message
“No data” in the table means that the table is inactive,
and no measurements have yet been performed.
Fig.37 shows the main screen of the
“REFLECTОMETER” mode, with two wires connected.
In Fig. 37:
2.8.1. Main Screen of the “REFLECTОMETER” Mode
The “REFLECTОMETER” mode can be activated from the Start Menu (2.2) or from the main screen the
“SWITCH” mode (2.4.1). The main screen of the “REFLECTОMETER” mode is shown in Fig. 36.