User`s guide

3-10
Triggering the Oscilloscope
External Trigger Input
2Press the External softkey to display the external trigger probe menu.
Probe Attenuation Turn the Entry knob to set the attenuation factor
displayed in the Probe softkey for the connected probe. The attenuation factor
can be set from 0.1:1 to 1000:1 in a 1-2-5 sequence.
For 2-channel oscilloscopes that have the Ext Trigger connector on the front
panel, when you connect an AutoProbe self-sensing probe, the oscilloscope will
automatically configure your probe to the correct attenuation factor.
The probe correction factor must be set properly for measurements to be made
correctly.
Probe Units Press the Units softkey to select the proper measurement unit
for the connected probe. Select Volts for a voltage probe and select Amps for a
current probe. Measurement results, channel sensitivity, and trigger level will
reflect the measurement units you have selected.
Input Impedance The 54620-series oscilloscope external trigger input
impedance is always 1 MΩ. The 54640-series oscilloscope external trigger input
impedance can be set to either 1M Ohm or 50 Ohm by pressing the Imped softkey.
• 50 Ohm mode matches 50-ohm cables commonly used in making high
frequency measurements. This impedance matching gives you the most
accurate measurements since reflections are minimized along the signal
path.
• 1M Ohm mode is for use with probes and for general-purpose measurements.
The higher impedance minimizes the loading effect of the oscilloscope on
the circuit under test.
For 2-channel oscilloscopes that have the Ext Trigger connector on the front
panel, when you connect an AutoProbe self-sensing probe, the oscilloscope will
automatically configure your probe to the correct impedance.
Attenuation
factor
Measurement
units
Input impedance
(54640-series)
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