H Heuer Instruments UMDT51A, Руководство пользователя

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Configuring the Tester
LT51 User Manual 29
LT51 Receiver
The LT51 Line Tester has powerful receiver measurement modes to display
level/power spectrums of signals at the RTX inputs. The following settings,
accessed by pressing the key, control how signals are received and
adjusted for correct display on the LCD.
Input Terminals
All measurements are made on the RTXa-b input terminal pair. Balance
measurements require the connection of a reference ground to the RTXg
terminal (*not available in this model)
Input Impedance
This is the impedance presented to sources connecting to the RTX terminals:

Press the key then [f1] to toggle Zrtx between 600

, 75

and 50

.
NOTE: If the transmitter output is set to RTX, any change in the input
impedance is reflected back to the output impedance. In this case, the
input impedance is normally bridged, except in the off-hook condition,
when it is terminated to sink loop current and hold the loop (see POTS
section
– a special hybrid is used to ensure the selected AC impedance
is provided for making POTS measurements
– it is only valid for
selected TX levels and RX ranges)
The current setting for
Zrtx is displayed in the CONFIG bar along the bottom of
the LCD.
Input bridging
To select whether the input impedance at the RTX terminals is bridged or
terminated:

Press the key, then [f2] to toggle Input between Term & HiZ.
NOTE: This setting will only have an effect when the Interface is set to TX-RX.
If the input is bridged,
HiZ appears before the value for Zrtx in the CONFIG bar
along the bottom of the LCD. If the input is terminated, only the Zrtx value is
shown.
Input level range

Press the key and then [f3] to select Rx Range.

Turn the rotary control clockwise to increase, or anti-clockwise, to reduce
the range.

Watch as the waveform display updates according to the selected range.

Press the key (or any key) to clear the dialog box.