HP 54710A User's Reference Manual page 103

Channel Menu
Probe
Units
Units lets you select unit of measure that is appended to the channel scale,
offset, trigger level, and vertical measurement values. These units are Volt,
Ampere, Watt, or unknown. You use Volt for voltage probes, Ampere for
current probes, Watt for optical-to-electrical (O/E) converters, and unknown
for other units or when you are not sure what the unit of measure is.
Ext gain and Ext offset
When you select Ampere, Watt, or unknown, two additional softkeys are
available: external gain and external offset. These two additional softkeys
allow you to compensate for the actual characteristics of the probe as
compared to its ideal characteristics. For example, you might have an
amplified lightwave converter whose ideal characteristics are 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.
Example Because the CAL signal on the mainframe is a voltage source, you can let the
Voltage probes
oscilloscope compensate for the actual characteristics of your probe by
letting the oscilloscope calibrate to the probe's tip. The following steps
illustrate how to calibrate voltage probes to the probe tip.
Set Atten units to ratio.
1
Set Units to Voltage.
2
Connect the probe to the front-panel
3
Press Probe cal Execute.
4
The oscilloscope automatically calibrates to the tip of the probe. The
calibration sets the probe attenuation correctly and automatically
compensates for any offset that the probe may introduce.
6–8
signal.
CAL