User`s guide

126 53220A/53230A User’s Guide

4 53220A/53230A Input Signal Conditioning

Input Coupling

The input to the 53220A/53230A counter is either DC (direct) coupled or AC

(capacitive) coupled, and is set using the the command:

INPut[{1|2}]:COUPling {AC|DC}

INPut[{1|2}]:COUPling? (query form)

AC coupling removes the signal’s DC content and centers the signal at 0V. The

measurable frequency range (channels 1 and 2) with AC coupling is:

• AC = 10 Hz - 350 MHz

• DC = 1 mHz - 350 MHz

DC coupling extends the frequency range across the full bandwidth of the

instrument (1 mHz - 350 MHz). CONFigure and MEASure do not change the

coupling setting. Following a reset (*RST) or front panel preset (Preset), the

coupling is set to

ΑC.

When selecting AC or DC coupling, the amplitude of the input signal must also

be considered. DC coupling is applicable for most measurements, especially

those requiring a specific trigger level. Rather than reducing the signal ampli-

tude by changing the counter range, AC coupling can be used to bring the sig-

nal in contact with the hysteresis window defined by the trigger level. This is

represented in Figure 4-2 (also see ‘Threshold Level and Sensitivity’).

C AC

10 Hz

1 mHz