Hi,
I did some measurements on the function generators available here in my lab.
I have limited myself to the audio region at 2V RMS output at a 50 Ohm load.
These THD measurements were done with Sine signals, if time is available, I will show from the generators also the square wave representation, but I will do that in a separate post.
All equipment used had been on for at least 1 hour before I started measuring.
These types of measurements take a fair amount of time and I have to do this in between my work. :-)
The equipment used:Hameg /R&S:
HMF2525Siglent:
SDG1032Siglent:
SDG2042Rigol:
DG4162The scope used for the THD pictures is a Hameg /R&S:
HMO3004And the THD meter is an Audio Precision:
Portable One PlusThe spectrum picturers are made with a
Siglent SDS2104 PlusFirst the SDG1032X14Bit Generator
This is the display of the Audio precision Analyser and it shows the measured THD at a bandwidth of 400Hz to 80KHZ, rounded off the THD is 0.07%.
.
This scope picture shows the measured 10KHz Sinus in the color yellow and the green trace is the residue of the Analyzer output.
Do not look at the size of the green trace, this is because the analyzer output is auto scale.
I only show the green trace to get an idea of what the THD looks like.
.
The following picture shows what the FFT looks like done with the Siglent scope.
Keep in mind that the table always varies a bit, especially at the somewhat higher harmonics.
Keep in mind the table value of -+1dB.
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Now the Siglent SDG2042X16Bit Generator
This is the display of the Audio Precision Analyser and it shows the measured THD at a bandwidth of 400Hz to 80KHZ, rounded off the THD is 0.007%.
.
This scope picture shows the measured 10KHz Sinus in the color yellow and the green trace is the residue of the Analyzer output.
Do not look at the size of the green trace, this is because the analyzer output is auto scale.
I only show the green trace to get an idea of what the THD looks like.
.
The following picture shows what the FFT looks like done with the Siglent scope.
Keep in mind that the table always varies a bit, especially at the somewhat higher harmonics.
Keep in mind the table value of -+1dB.
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Now the Hameg HMF252514Bit Generator
This is the display of the Audio Precision Analyser and it shows the measured THD at a bandwidth of 400Hz to 80KHZ, rounded off the THD is 0.023%.
.
This scope picture shows the measured 10KHz Sinus in the color yellow and the green trace is the residue of the Analyzer output.
Do not look at the size of the green trace, this is because the analyzer output is auto scale.
I only show the green trace to get an idea of what the THD looks like.
.
The following picture shows what the FFT looks like done with the Siglent scope.
Keep in mind that the table always varies a bit, especially at the somewhat higher harmonics.
Keep in mind the table value of -+1dB.
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Now the Rigol DG416214Bit Generator
This is the display of the Audio Precision Analyser and it shows the measured THD at a bandwidth of 400Hz to 80KHZ, rounded off the THD is 0.011%.
.
This scope picture shows the measured 10KHz Sinus in the color yellow and the green trace is the residue of the Analyzer output.
Do not look at the size of the green trace, this is because the analyzer output is auto scale.
I only show the green trace to get an idea of what the THD looks like.
.
The following picture shows what the FFT looks like done with the Siglent scope.
Keep in mind that the table always varies a bit, especially at the somewhat higher harmonics.
Keep in mind the table value of -+1dB.
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Now the Audio Precision: Portable One Plus - GeneratorAnalog Generator
This is the display of the Audio Precision Analyser and it shows the measured THD at a bandwidth of 400Hz to 80KHZ, rounded off the THD is 0.0008%.
THD with my PC and a verry good Soundcart is about 0.0002.
.
This scope picture shows the measured 10KHz Sinus in the color yellow and the green trace is the residue of the Analyzer output.
Do not look at the size of the green trace, this is because the analyzer output is auto scale.
I only show the green trace to get an idea of what the THD looks like, this is almost all noise...
.
The following picture shows what the FFT looks like done with the Siglent scope.
Keep in mind that the table always varies a bit, especially at the somewhat higher harmonics.
Keep in mind the table value of -+1dB.
.
And what does the last picture, which is the FFT from de AP generator on the Siglent Scoop show us now....
The Siglent scope I used, does not have sufficient capabilities to make good FFT measurements below say 50dB.
The slightly newer 12Bit Siglent series scoops will do 15 to 20dB better I think, the SDS2104X is a basic 8Bit scoop with 10Bit oversampling.
Later I will show some pictures of the square wave the generators can make.
Kind regards,
Bram