Global Specialties 4005 - Manual - Manual (Page 15)

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C. It is easier to accurately set the FREQ. dial if settings between 0.1 and 5.0 are used. Since the
dial rotation overlaps ranges, it is not usually necessary to use readings below 1. If this occurs,
change to a lower range and use a higher dial setting.
A . Z e r o D C O f f s e t
w i t h m a x i m u m s i g n a l
B . O f f s e t l i m i t s
w i t h o u t C l i p p i n g
C . E x c e s s i v e O f f s e t
a l l e x a m p l e
o u t p u t t e r m i n a t e d i n 5 0
+ 5 V
0 V
- 5 V
+ 5 V
0 V
- 5 V
+ 5 V
0 V
- 5 V
P o s it iv e
D C O f f s e t
N e g a t iv e
D C O f f s e t
P o s it iv e
D C O f f s e t
N e g a t iv e
D C O f f s e t
Figure 4. USE OF DC OFFSET CONTROL
D. The main output BNC is labeled 50 . This means that the source impedance is 50 , but the
output may be fed into any circuit impedance. The output level varies in proportion to the
terminating impedance. If it is desired to maintain a constant output level while injecting signal
into various circuits with various impedance, constant terminating impedance is necessary.
When the generator output is connected to a coaxial connector on the equipment under test,
it ’s usually a moderate to high impedance. A reasonably constant terminating impedance may
be maintained while injecting signal into moderate and high impedance circuits (500 and up)
by adding a coaxial tee in the output cable and connecting a 50 termination to one leg.
Remove the 50 termination when injecting into a 50 circuit. Also, to keep DC injection point,
the DC offset should be set to match the circuit voltage, or blocking capacitor may be required
to avoid DC loading with 50 .
E. When using the higher output frequencies while using the square wave output, terminate the
cable in 50 to minimize ringing. Keep the cables as short as possible.
F. To set output amplitude to a specific level, measure peak to peak amplitude on an oscilloscope.