Stanford Research Systems DS345, Manual

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Function Setting
2-10
FUNCTION SELECTION
The DS345's output function is selected using the FUNCTION UP/DOWN ar-
row keys. Simply press the keys until the desired function LED is lit. If the
programmed frequency is outside of the range allowed for the selected func-
tion, an error message will be displayed and the frequency will be set to the
maximum allowed for that function. If modulation is enabled and the modula-
tion type or parameters are incompatible with the new function, an error mes-
sage will be displayed and the modulation will be turned off (the parameters
will not be altered).
Ramps
Ramp functions usually ramp up in voltage, however, downward ramps may
be programmed with the output invert function (see AMPLITUDE section).
Arbitrary Functions
Arbitrary functions may be created on a computer and downloaded to the
DS345 via the computer interfaces, or they may be created using the
DS345's front panel editing functions. Arbitrary waveforms normally repeat
continuously, single triggering and burst triggering of arbitrary waveforms is
accomplished using the DS345's BURST modulation function. (See the AR-
BITRARY WAVEFORM EDITING section for more detail.)
FREQUENCY
To display the DS345's output frequency press [FREQ]. The frequency is al-
ways displayed in units of Hz. The DS345 has 1
µ
Hz frequency resolution at
all fre quencies, for all functions. The maximum frequency depends on the
Function Frequency Range
Sine 1
µ
Hz
→
30.200000000000 MHz
Square 1
µ
Hz
→
30.200000000000 MHz
Triangle 1
µ
Hz
→
100,000.000000 Hz
Ramp 1
µ
Hz
→
100,000.000000 Hz
Noise 10 MHz White Noise (fixed)
Arbitrary 0.002329Hz
→
40.0 MHz sampling
function selected as listed below:
Frequency is usually displayed by the DS345 with 1 mHz resolution. Howev-
er, if the frequency is below 1 MHz and the microhertz digits are not zero the
DS345 will display the frequency with 1
µ
Hz resolution. At frequencies great-
er than 1 MHz the digits below 1 mHz cannot be displayed, but the frequency
still has 1
µ
Hz resolution and may be set via the computer interfaces or by
using the MODIFY keys with a step size less than 1 mHz.
If the function is set to NOISE the character of the noise is fixed with a band
limit of 10 MHz. The frequency is not adjustable and the FREQ display will
read "noise" instead of a numerical value.
If the function is set to ARB the frequency displayed is the
sampling fre-
quency
of the arbitrary waveform. This number is independent of the usual
frequency; it is the dwell time that the DS345 spends on each point in an ar-
bitrary waveform. This sampling frequency must be an integer submultiple of
the the 40 MHz clock frequency. That is, 40 MHz/N where N = 1,2,3... 2
34
-1
(40 MHz, 20 MHz, 13.3333 MHz, 10 MHz, ...). The DS345 will spend