Agilent Technologies 54622D Especificações descarregar pdf (Página 9)

Features to Try - Averaging:

Our building, and most laboratories, are “dirty” in the electromagnetic sense. This is due to the

power line noise, computer systems, lighting, and RF (radio-frequency) signals that create

unwanted voltages on top of the voltages we do want to measure.

One way to minimize the problem (clean up the “dirt”) is to use the Averaging feature of

a digital ‘scope. Look closely at the waveform below, on the left. It is the Probe Comp

squarewave, and shows a “fat” line for the upper and lower parts of the square wave. This is

caused by the noise voltage superimposed on top of the signal voltage.

In the waveform below on the right, Averaging has been turned on, using 8 averages. Note

that the tops and bottoms of the square wave are much “thinner” (i.e. less noise is present),

because the noise has been averaged out of the display.

YOU DO IT: Now try it yourself, using the probe compensation signal on the front panel.

1) Get back to the basic factory default settings, use Autoscale and look at the Probe Comp

waveform. You should see the display shown above on the left (averaging is OFF now).

2) Press the Acquire hardkey in the Waveform section of the front panel, and turn on

averaging by pressing the Averaging softkey. You should now see the display shown above

on the right (averaging is ON).

Note that the number of averages (# of Avgs) can be changed, as needed, over a wide range of

values (the default number is 8). This feature may create problems. To see the effect of a

large number of averages, do the following:

3) Turn averaging OFF (by pressing the NORMAL softkey). Remove the probe tip from the

Probe Comp output, then reconnect it. Note the nearly instantaneous change in the display

(from squarewave to flat line).

4) Now turn averaging ON and set the # of Avgs to 8. Remove the probe tip from the Probe

Comp output, then reconnect it. Note that the change in the display (from squarewave to flat

line) is rapid, but gradual (i.e. it is not instantaneous). Leave the probe disconnected.

Probe Comp Signal, No Averaging

Probe Comp Signal, With Averaging

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Agilent Technologies 54622D Especificações Página 9