Stanford Research Systems DS360 Operating Manual And Programming Reference page 107

5. Harmonic Distortion and Noise
These tests check the harmonic distortion for sine and square waves.
Setup
Set the spectrum analyzer input to shield grounded with AC coupling. Obtain the notch filters described
on page 6-5.
Procedure
1) Reset the DS360 (Turn power off, wait 2 seconds, then turn power on w/ [CLR] pressed.
2) The distortion is verified at 2 amplitudes and 3 frequencies. Set the spectrum analyzer to
exponential vector averaging, with 50 averages and dBV
amplitude setting below, perform 2a through 2d.
Frequency
1.0 kHz
11 kHz
31 kHz
a) Connect the + output of the DS360 to the Spectrum analyzer through the appropriate filter.
b) Set the spectrum analyzer to the appropriate span and input range. Wait for the display to
settle.
c) Measure the 2nd through 5th harmonics values and calculate the THD (total harmonic
distortion) as described in the beginning of the section. Record the THD value on the test record.
d) Connect the - output to the notch filter and perform steps 2b and 2c for the - output.
3) The residual output noise is verified at the same 2 amplitudes and 3 frequencies as the distortion.
Set the spectrum analyzer to measure PSD (power spectrial density) with exponential RMS
averaging, 50 averages and V
perform 3a through 3d.
a) Connect the + output of the DS360 to the Spectrum analyzer through the appropriate filter.
b) Set the spectrum analyzer to the appropriate span and input range. Wait for the display to
settle.
c) Measure the noise at non harmonically related points. Avoid frequencies near the fundamental,
since they are effected by the notch filter. Record the noise value on the test record.
d) Connect the - output to the notch filter and perform steps 3b and 3c for the - output.
4) The even harmonics of the square wave are measured at 2 points, 1 kHz and 20 kHz.
Set the spectrum analyzer to measure spectrum with exponential RMS averaging, 10 averages, 6
dBV input range and dBVrms units.
Span Input Range (1V
0 to 12.5 kHz
0 to 100 kHz
0 to 100 kHz
units. For each frequency and amplitude setting in step 2,
RMS
Performance Tests 6-13
units. For each frequency and
RMS
) Input Range (10V
RMS
-36 dBV
-36 dBV
-36 dBV
DS360 Ultra Low Distortion Function Generator
)
RMS
-22 dBV
-22 dBV
-22 dBV