Fluke DDS Function Generator 271 User Manual

Page 24

271
Getting Started Manual

Effect of the output attenuator

The instrument has an output attenuator with fixed steps
of 20 dB. The attenuator follows the output stages so any
dc offset added to the waveform is subject to the
attenuator.

With the waveform amplitude set to 4 V p-p the attenuator
is switched out; however if you adjust the output to (say)
0.4 V p-p, 20 dB of attenuation is switched in. When this
happens you will be warned that the dc offset has been
changed.

Try it. Set the amplitude to 4 V p-p and the dc offset to
+1.5 V.

Now change the amplitude by pressing AMPL, 0.4, V. The
instrument will beep and you should see something like
this for a few seconds:

**** WARNING 07 ****
* DC OFFSET CHANGE *
* BY OUTPUT LEVEL *
********************

Then this:

PER =80.00000us
VhiZ=+4.00 Vpp 50

Ω

DC=+1.50 V (+151.mV)
SYM=50.0% (50.0%)

The figure in brackets to the right of the programmed dc
offset is the value which results from the application of
20 dB of attenuation. It may differ slightly from the
calculated value (150 mV) because of the attenuator's
saved calibration factors.