of the instrument is achieved by switching in up to five -10dB attenuation stages. For generator
amplitudes in the range ~6·3Vpp to 20Vpp (20Vpp -10dB
≈
6·3V) a corresponding signal range at
SUM IN to force the generator output to 20Vpp would be ~5Vpp to 0V. If, however, the generator
amplitude is in the range 630mV to 2·0Vpp (i.e. 20dB fixed attenuation switched in) the same
signal range (~5Vpp to 0V) at SUM IN will only force the generator output to 2·0V; increasing the
SUM IN signal beyond ~5Vpp will drive the amplifier into clipping without further increasing the
amplitude. A table of the approximate amplitude ranges corresponding to each attenuator step is
given at the end of this section. Within each range a SUM IN signal of ~5Vpp will force the output
from range minimum to range maximum; if the amplitude is set to mid-range (e.g. 13V on the top
range) the SUM IN signal needed to force the output to range maximum is about half, i.e. 2.5Vpp
in this example.
A simple way to set the desired output levels for both waveforms being summed is as follows:
1.
With no signal into SUM IN set the waveform, frequency and amplitude of the first signal
e.g. 10Vpp, 1kHz, sinewave.
2.
Select dc waveform on the generator and connect the other signal to SUM IN; the output
waveform should change from dc to that applied to SUM IN. Adjust the level of the SUM
IN signal to get the desired amplitude from the generator, e.g. 10Vpp.
3.
Reselect sine. The output should be the sum of the two signals with an amplitude of, in
this example, approximately 20Vpp.
Amplitude Range for Each Attenuator Step
Attenuation (dB)
Output range (hiZ)
0
6·3V - 20Vpp
10 2·0V-
6·3Vpp
20
0·63V - 2·0Vpp
30
200mV - 630mVpp
40
63mV - 200mVpp
50
20mV - 63mVpp
36