Megger SMART THUMP ST16, Руководство пользователя

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M
AVTMST16 Rev 1 May 2016
18
System Settings (only accessible in Expert Mode)
In order to change the system settings, EXPERT settings from the main
menu must be accessed.
These settings are only available, if the system is operated in Expert Mode . If
this is not the case, the rotary knob must pushed down and held down
shortly on any of the main menu icons until the system displays the prompt for
the password, which is required to activate the
Expert Mode . The default
password is “0000” (can be changed – see below).
After activation of the EXPERT MODE , you are automatically forwarded to
the system settings:
Menu item Description
Leave EXPERT
MODE By leaving the expert settings through this menu item the new settings are saved
and the system is switched to
QUICK STEPS mode .
The is no longer be displayed in the main menu which prevents unauthorized
persons from changing the system and default settings.
Date / Time Date and time settings
Language Language settings
Default Settings
>> Measurement
unit
Length Unit of the x-axis ( Meter , Feet or Time ).
If set to Time , the actual runtime of the pulse is displayed and no
conversion to length of cable is performed.
Rate Only available, if Length is set to Meter or Feet
Rate refers to how the propagation velocity of the TDR pulse is
specified. This can be done
either relative to the speed of light ( % of
NVP ) or in absolute units in
μ
s (
μ
sec = microseconds = 10
-6
sec ).
>> V/2 or NVP Only available, if Length is set to Meter or Feet
Propagation velocity of the cable under test can be expressed as
percentage of speed of light (NVP), e.g. 0.53 corresponds to 53% of speed of light
V/2 (half of the actual velocity of propagation) in m/
μ
s
>> Trigger delay
time
Delay time between the time of flash-over at the fault and the time to trigger and
capture the TDR trace. The delay time allows the flash-over to build up well before
a measurement is done (ideally when the arc reaches it highest current).
If Delay time too short: Flash-over is not fully developed and may cause poor or
no reflections of the TDR pulse.
If Delay time too long: Flash-over is extinguished already when TDR pulse
arrives and reflection measurement is too late. Thus, the fault trace looks identical
to reference trace.
The default value for the ST16 is 700 µms.