Stanford Research Systems DS345, Manual

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Function Setting
2-11
1/ Fsample on each point. When a new sampling frequency value is entered
the DS345 will round the value to the nearest integer submultiple of 40 MHz.
Note that the frequency for the standard functions is
never
rounded.
Setting the Frequency
To set the frequency of any function simply type a new value on the keypad
and complete the entry with the appropriate units (Hz, kHz, or MHz). The
MODIFY keys may be used to increase or decrease the frequency by the cur-
rent step size. Press [STEP SIZE] key to display and change the step size.
AMPLITUDE
Pressing [AMPL] displays the amplitude of the output function. The amplitude
may be set and displayed in units of V
pp
, V
rms
, and dBm. The current units
are indicated by the LEDs at the right of the display. The amplitude range is
limited by the DC offset setting since |V
ac peak
| + |V
dc
| ² 5 V. If the DC offset
is zero the amplitude range for each of the functions is shown below:
note
: The rms and dBm values for NOISE are based on the total power in the
output bandwidth (about 10 MHz) at a given peak to peak setting.
V
pp
V
rms
dBm (50
Ω
)
Function Max. Min. Max. Min. Max. Min.
Sine 10V 10 mV 3.54V 3.54 mV +23.98 -36.02
Square 10V 10 mV 5V 5 mV +26.99 -33.0
Triangle 10V 10 mV 2.89V 2.89 mV +22.22 -37.78
Ramp 10V 10 mV 2.89V 2.89 mV +22.22 -37.78
Noise 10V 10 mV 2.09V 2.09 mV +19.41 -40.59
Arbitrary 10V 10 mV n.a. n.a. n.a. n.a.
Arbitrary function amplitude may
only
be set in units of V
pp
. The output sig-
nal will briefly go to zero as the output attenuators are switched.
The units of the amplitude display may be switched between V
pp
, V
rms
, and
dBm without changing the actual amplitude by pressing the corresponding
units key. When the DS345 is switched from one function to another the
peak-to-peak amplitude is held constant. If the DC offset is zero, the ampli-
tude may be set with three digits of resolution. If the DC offset is not zero the
larger of the amplitude and the offset determines the resolution of both pa-
rameters. The amplitude display is automatically adjusted such that all of the
digits that may be changed are displayed.
Output Inversion
For ramp and arbitrary functions the DS345's output may be inverted. This is
useful for turning positive ramps into negative ramps, or inverting arbitrary
waveforms. Pressing [AMPL] two times displays the invert enable option.
Use the UP/DOWN MODIFY keys to enable or disable the inversion.
D.C. Only
The output of the DS345 may be set to a DC level by entering an amplitude
of 0V. When the amplitude is set to zero the A.C. waveform will be off and
the DS345 may be used as a DC voltage source. If the amplitude is zero the
display will read "no AC" when the units are set to dBm.
TTL Settings
Pressing [SHIFT][TTL] sets the output amplitude and offset to TTL values.