Hameg HM8131-2 Handbuch Seite 61

sine wave of 1 kHz and 1.0 V
rms
In this case the modulation depth can be set between 0 .. 100
%, this being equeivalent to internal modulation.
External source: V = 1.4 V , 1 kHz, 1 V/cm
in p
HM 8131-2: V = 10 V , 20 kHz, 5 V/cm,
o pp
100 % modulation selected
For 50 % modulation this picture will result:
External source: V = 1.4 V , 1 kHz, 1 V/cm
in p
HM8131-2: V = 10 V , 20 kHz, 5 V/cm,
o pp
50 % modulation selected
A further method of varying the modulation depth
with external modulation is by changing the input
voltage. The following example shows the same
output signal as before with an input of ½ = 0.5 V
and the modulation depth set to 100 %. The am-
plitude is 0.7 Vp as before. This method is advan-
tageous especially in automated test
systems.
HINT
(equal to the internal source).
rms
M a i n m e n u 2 a n d i t s f u n c t i o n s
External source: Vin = 0.5 V
rms
HM 8131-2: Vo = 10 V
pp
100 % modulation selected
If it is desired to modulate the instrument exter-
nally from 0 to 100 % the amplitude of this signal
must range from 0 to 1.4 Vp, the modulation depth
remains set to 100 %. The amplitude may be in-
creased to 3.00 Vp while simultaneously decreasing
STOP
the modulation depth setting of the instrument.
Higher voltages will overmodulate as demonstrated
in the pictures following:
External source: Vin = 4.00 Vp, 1 kHz, 2 V/cm
HM8131-2: Vo = 10 Vp, 20 kHz, 5 V/cm,
100 % modulation selected
generator overmodulated
External source: V = 4.00 Vp, 1 kHz, 2 V/cm
in
HM 8131-2: V = 10 Vp, 20 kHz, 5 V/cm,
o
35 % modulation selected
generator overmodulated
= 0.7 Vp, 1 kHz, 1 V/cm
, 20 kHz, 5 V/cm,
Subject to change without notice
59