Tektronix TCP300 Series, User Manual, Page: 42 / 80

Reference Notes
AC and DC Coupling
You can couple the signal input to the TCPA300 and TCPA400 with either DC
or AC coupling. DC coupling shows the DC and AC measurement components
while AC coupling removes the DC component from the displayed signal. When
you use AC coupling, make sure that the input DC current does not exceed the
probe speci
fi cations.
AC coupling will affect waveforms at frequencies higher than the AC Coupling
Low-Frequency Bandwidth. For example, pulsed currents may exhibit rolloff or
decreased amplitude. (See Figure 12.)
1. A low-frequency square wave using AC coupling. The signal exhibits
low-frequency rolloff.
2. By changing the ampli fi er coupling to DC, the pulse is displayed as truly
square, as shown.
Figure 12: Effect of AC or DC coupling on low-frequency signals
If you are trying to examine a low-frequency signal that is superimposed on a
comparatively large DC component, you can resolve the signal by performing
these steps:
1. Select the range setting that will display the maximum detail without
exceeding the dynamic range of the signal.
2. Adjust the oscilloscope V/div sensitivity (A/div if using the TEKPROBE
interface), to display maximum signal detail.
24 TCPA300/400 Ampli fi ers and TCP300/400 Series Current Probes User Manual