HP 54753A User Manual page 41

The attenuation range is from 0.0001:1 to 1,000,000:1. When you connect a
compatible active probe to the probe power connector, adjacent to the
corresponding channel input, the instrument automatically sets the
attenuation. For all other devices, set the probe attenuation with the knob,
arrow keys, or keypad.
The Attenuation function is not available when ohm, % reflect, or gain units are
selected.
Channel Alternate scale . . . Attenuation
Key Path
Units
The Units function lets you select the unit of measure appended to the channel
scale, offset, trigger level, and vertical measurement values. For the plug-in
module, the units are volts, watts, amperes, ohms, % reflect, gain, or unknown.
Use volt for voltage probes, ampere for current probes, watt for optical-to-
electrical (O/E) converters, and unknown when there is no unit of measure or
when the unit of measure is not one of the available choices. The gain selection
is only available when the channel has been chosen as a TDT destination.
The two additional choices, ohms and % reflect are selectable once a TDR/TDT
normalization and reference plane have been established (see the 54753A Setup
Menu or 54754A Setup Menu chapter under Establish normalization & ref plane
for more information). Use Ohms when TDR/TDT vertical scale units of ohms/
div are required for making measurements. Use % reflect when TDR/TDT
percentage of reflection units are required.
Channel Alternate scale . . . Units
Key Path
Ext gain and Ext offset
When you select ampere, watt, or unknown on an electrical channel, two
additional functions become available: External Gain and External Offset.
These two additional functions allow you to compensate for the actual
characteristics of the probe rather than its ideal characteristics. For example,
you might have an amplified lightwave converter with ideal characteristics of
300 V/W with 0 V offset. But, its actual characteristics are 324 V/W with 1 mV
of output offset. Therefore, set the External Gain to 324 V/W and the External
Offset to 1 mV.
Refer to "Calibrating Voltage Probes" for information on calibrating to the tip of the
probe.
Setup Channel Menu
Alternate scale. . .
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