H Heuer Instruments UMDT51A, User Manual

Page: 42 / 104

Configuring the Tester
LT51 User Manual 30
If the currently selected level range is not optimal for the signal being measured,
one of the following range indicators appears on the LCD:

“RNG” if the range should be reduced to measure the smaller signal.
or

“OVLD” if the range should increased to accommodate the larger signal.
NOTE: setting the RX range, automatically clears AutoRange to OFF.
AutoRange
Enables the tester to automatically select the optimum input level range and
frequency span for any given input signal, to avoid overloading input circuits:

Press the key and then [f4] to toggle AutoRange between OFF, LVL
only and LVL+BW.
NOTE: When AutoRange=LVL+BW, and the frequency span is set manually,
AutoRange is changed to LVL only.
NOTE: When AutoRange=LVL+BW, and the following conditions are set, BW
autoranging is disabled although the setting is not changed:
- during AutoTest mode.
-
when sweeping is active.
- when connected to a slave LT51.
-
If any filter is set.
- If the centre frequency is > 0 Hz.
Interface
The transmitter can be selected to output a signal only at the TX terminals (TX-
RX interface mode or 4-Wire) or also at the RTX terminals (RTX interface mode
or 2-Wire). Ztx and Zrtx can only be set independently when the interface mode
is set to TX-RX and the transmitter output is directed to the TX terminals.
When RTX is selected as the interface, the LT51 output circuit is connected to
the RTX terminals and hence the input circuit of the LT51. The impedance seen
at the RTX terminals is provided by Ztx, and the input impedance is bridged. As
the output circuit is still connected to the TX terminals, care must be taken not to
load the TX terminals (see also POTS section):

Press the key, then [f5] to toggle Interface between TX-RX and RTX
The current setting for
Interface is displayed in the CONFIG bar along the
bottom of the LCD.