Stanford Research Systems DS345, Manual

Page: 99 / 139

Calibration
6-8
Sinewave Amplitude
This calibration corrects the flatness of the DS345's sinewave output. This
calibration depends on frequency and is calibrated at 98 frequency points in
the DS345's frequency range. The carrier null calibration should be done be-
fore this calibration.
1) Set the DS345 to sine wave, 1 kHz, 3 Vrms, 0 V offset. Set the frequency
step size to 312500 Hz. Connect the DS345's output to the thermal convert-
er and the thermal conveter output to the DC voltmeter.
2) Set calbyte 20 to 16384.
3) Allow the thermal converter output to settle (about 10 - 15 seconds) and
record the voltage as Vref (the voltage should be about 7 mV).
At 96 frequencies between 313500 Hz and 30,001,000 Hz in 312500 Hz
steps repeat the following procedure.
4) Set the DS345's output frequency and allow the converter to settle. The
new calbyte for this frequency is given by:
The calbyte should be in the range 8000 to 23000. The calbyte number for a
given frequency is: number = 20 + (f - 1000Hz)/312500 Hz (that is 313500
Hz = 21, 626000 Hz = 22, etc.).
5) Set calbyte 117 to the same value as calbyte 116.
Square Wave Amplitude
This calibration corrects the DS345's square wave amplitude response. This
calibration depends on frequency and is calibrated at 98 frequency points in
the DS345's frequency range. The square wave symmetry calibration should
be done after this calibration.
1) Set the DS345 to square wave, 1 kHz, 10 Vpp. Connect the DS345's out-
put to the oscilloscope with a 50
Ω
terminator. Set the DS345's frequency
step size to 312500 Hz. Set the oscilloscope to 2 V/div vertical and 1 ms/div
horizontal.
2) Set calbyte 118 to 16384.
3) Measure the peak-to-peak amplitude of the square wave and record as
Vref.
At 96 frequencies between 313500 Hz and 30,001,000 Hz in 312500 Hz
steps repeat the following procedure.
4) Set the DS345's output frequency and measure the peak-to-peak ampli-
tude. The new calbyte value for this frequency is: new calbyte = old calbyte *
(Vref/Vpp). The calbyte should be in the range 8000 to 23000. The calbyte
new calbyte
=
old calbyte
×
V
ref
V
dc








0.556