Sekotech ST-300 SPIDER, Руководство по эксплуатации, Страница: 31 / 68

OPERATING MANUAL
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2.8.1.1 Setting the Velocity Factor (Inverse Value)
A reciprocal value of the velocity factor is used throughout. By default it is set at 1.5 (so the velocity
factor equals approximately 0.66, which corresponds to an SQR-2 type cable).
To set a different reciprocal of the velocity factor, press “F2” (Fig.38).
2.8.1.2 Cable Settings
To set the type of cable, press “FUNC”. Proceed to set the cable type and the number of wires
connected, in the same manner as described in 2.5.1.1. To exit from the cable settings menu to the main
screen of the “REFLECTОMETER” mode, press “ESC” or “FUNC”.
2.8.1.3 Measurements in the Main Screen
Before starting measurements, set the pair of wires to be tested. This can be done in the “SWITCH”
mode (2.4.1), or using the table view in the “REFLECTОMETER” mode (2.8.2), or in other modes with a
similar option. Cable type and the number of cores are also to be indicated (2.8.1.2). It is important that
the numbers of wires selected for testing are not excluded as a result of an erroneous setting, otherwise
no measurements will be taken, and the active table will read “No defects”.
The measurement cycle will start automatically on entering the main screen of the “REFLECTОMETER”
mode. During the measurement cycle which may take up to 15 sec, the active table will read “Measuring”
and show running dots.
Upon completion of measurements, the results will be shown in the active table (3-5, Fig.37).
A new measurement cycle can be started by pressing “ENTER”. Data in the active table will be updated.
Caution! Under the conditions of strong inductive and/or capacitive reactance, the induced voltage in
the tested cable (even if it is de-energized) may turn out to be too high. If this happens, the reflection
meter will be disabled, and the message “Noise” will appear in the active table. For further tests on the
cable, the causes of such powerful interference must be found and eliminated.
Controls in the “REFLECTОMETER” mode:
– table selection
“ENTER” – start a new measurement cycle in the active table
“F1” – exit to the “SWITCH” mode
“ESC” – exit to the Start Menu
“F2” – set reciprocal velocity factor
“FUNC” – go to the cable setting menu
“MODE” – go to the automatic mode
If voltage in the connected wire pair is /-3V, the pair cannot be tested in the reflection meter
mode. The presence of excessive voltage is indicated by the sign in place of the selected pair
number (2, Fig.37). To proceed with testing, disconnect the cable from the power source (de-energize
the tested circuit).
Fig.38
Use the and keys to change the digit position, and the and
keys to adjust the value. To return to the main screen, press “F2”, “ESC”
or “ENTER”.
The new reciprocal of the velocity factor will be shown as the subscript of
the “F2” hotkey (7, Fig.37).
For any known value of velocity factor (VF) found in reference sources and sometimes given in
percentages, the reciprocal (1/VF) is to be used, which should always be >1. For instance, if VF = 66
percent, the calculation is 1/0.66, which is approximately equal to 1.5.