Agilent Technologies 54641A Service Manual page 56

Figure 3-4
Testing Performance
To verify voltage measurement accuracy
Y2
Use a Blocking Capacitor to Reduce Noise
On the more sensitive ranges, such as 2 mV/div and 5 mV/div, noise may be a factor.
To eliminate the noise, use a BNC Tee, blocking capacitor, and BNC shorting cap to
shunt the noise to ground. See figure 3-4.
To Power Supply or
Calibrator
Using a Blocking Capacitor to Reduce Noise
Blocking
Capacitor
To oscilloscope input
BNC shorting
cap