IMD-SMPTE vs Amplitude Plot

[lemon]

I tried to modified the file THD(dB)_vs_OutputdBFS_RTX6001, thus to have a IMD-SMPTE vs Amplitude (both channels) measurement for dac's measurements purposes.
It seems that all routines running well, but there is no any capturing in X-Y Plots.
Additional, I see that the record button stills in red condition, not green as it should.

Can someone to help me about this?

[lemon]

My mistake was that I changed the Alias name of Derived Data Point (DDP).
For example the DDP IMD_A(dB) has an Alias IMD_A(dB), this alias is the text that presented on X-Y axis.
Because I don't like the text "IMD_A(dB)" but I preffer the "IMD-SMPTE (dB), Ch. A", I changed the Alias text. And the problems begun...

Now I have a right dtp file that works well every time that running (see the capture).

But, I would like to improve it.
This dtp file opens the psf file \psf\RTX6001\IMD_SMPTE_60Hz(4)_7kHz(1)_FFT131072_R TX6001.psf that has a specific ADC Input Level. Accordingly to this level the precise of IMD measuring changing.
See the attachments files, they are IMD-SMPTE capturing in different ADC Input Levels.
As you can see the low or high level of capturing relates with the input aplitude of ADC.
Here, I prefer to determine the exactly ADC level at the dtp file to have an optimum capturing of IMD.
The manual of Mi-Pro says that the SIR Instruction set the input Range by A-Amplitude (V) area.
This area can be a real number (V) or variable (x1-x5), but I have error with all of that. All the time I have the message "Measuring range not supported"

Any help about this?

[lemon]

I forget to include the dtp file.

[VirtinsTech]

Thank you for your questions.

1. Your first DTP uses Variable x3 for the output dBFS of the DUT and Variables x1 and x2 for the Input Ranges of the two input channels of RTX6001. It contains an auto-ranging function. The auto-ranging function starts the Input Range of RTX6001 from the lowest one: 0.1414V, conducts a trial run (the two "sio*" steps. The first one is used to actually switch the Input Range. It allows RTX6001 to become stable after the possible relay switching before the trial measurement is performed by the second one) and steps up by 10dB (the RTX6001’s attenuation incremental) if the measured PeakLeveldBFS in the trial run is greater than -3dB. The last “SIO” step is the real measurement and the DDPs obtained in this step are used for the X-Y Plots.

There are two errors found in this DTP:

(1) As you have already found out, the aliases of the DDPs to be captured “IMD-SMPTE, Ch.A (dB)” and “IMD-SMPTE, Ch.B (dB)” contain a comma “,”, which is unfortunately the control character in the DTP file (a Comma Separated Variable (CSV) file). It interferes with the data parsing when loading a DTP file. We have thus tightened the input validation of the alias edit box in the DTP configuration panel. Thank you so much for your finding.

(2) The DDPs to be captured include RMSDBV_A(dBEU) and RMSDBV_B(dBEU). But the loaded Panel Setting File “RTX6001\IMD_SMPTE_60Hz(4)_7kHz(1)_FFT131072_RTX6001.psf” does not contain the instrument to supply these two values. The Multimeter window needs to be opened in dBV mode to do that. By the way, this DTP is slow because this PSF file has a linear inter-frame average of 10 frames. It can be removed if the average is not required.

When you run this DTP, you will find that "NA" is displayed as the values for the DDPs to be captured in the last "SIO" step. Thus the X-Y Plots show no data.

The attached DTP file has corrected the above two errors.

IMD-SMPTE(dB) vs Amplitude(dBFS).zip

(1.17 KiB) Downloaded 1857 times

2. Your second DTP specifies the output dBFS and Input Ranges explicitly but does not contain the above auto ranging function which causes the problem mentioned. Although it is still possible to implement the above auto ranging function in this way, the number of steps required will be much more than the first DTP in which variables are used instead. When the SIR instruction is used, the input range value must be within 5% of the hardware supported, otherwise, "Measuring range not supported” error message will pop up. Please also note that the SIR instruction does not actually switch the Input Range until a SIO or STI instruction is implemented.

[lemon]

Many thanks for the help.

At the case-1

1) yes, it is very slow procedure, I removed the Intra_Frame_Procedure (but I think that some kind of average is needed for better normalized data) and at the steps 10&11 (SIO), I changed the Duration to 1s
I think the measuring from a -153dB level, it is not necessary here, a range from -100dB to 0 dB it will be enough. Is that configurable this?

2) the first capture was made from yours dtp file - without any change - as you can see, there are 3 issues
- there are two "humps", that caused from the -3dB limit, at the -3dB the IMD rise up.
- there is a peak, that caused from gen output changing from 0.1 to 1Vrms, I don't know how this can by resolved at this point the IMD rise from 0.005 to 0.01%
- the measuring stops at the -23dB, is it relates with variable x4? What must change for 0dB (RTX-6001 loopback). Could this to be configurable for any dac output?

3) the second capture was made with yours dtp, but with -5dB at steps 12 & 15 (CHK), the Duration -> 1sec (Steps 10&11) & the Intra_Frame_Procedure has removed from the psf file.
- the two "humps" seems to normalized
- the peak is the same
- the stop at the -23dB remaining
- better speed of test.

In conclusion, what changes must to done, to have a measure from -100dB, what must is done to eliminate the peak of gen output changing and at the end if we could to have a configurable level max. output for all dac outputs measuring.

For the case-2, I will see better the rest of instructions that needs and I'll come back about it.

Thanks for your time to spend me, again.

[lemon]

...In conclusion, what changes must to done, to have a measure from -100dB....

- OK, I found it, I changed the x3 to 0.0002V and I have an almost -97.7dB low end range capturing...now I can modified depends my needs this parameter.

The new capture that I have included is with:
- Intra-Frame Proc. 5 (linear)
- x3=0.0002
- x2 variable has removed and I don;t know what is the role of it for 2x to Ch.B, perhaps it was still from initial dtp file that I had modified (thd, thd+N vs Magnitude).

Let us focus to the spike and how can I take a 0dBFS measurement (upper limit range).

At the last, you had wrote me "(2) The DDPs to be captured include RMSDBV_A(dBEU) and RMSDBV_B(dBEU). But the loaded Panel Setting File “RTX6001\IMD_SMPTE_60Hz(4)_7kHz(1)_FFT131072_RTX6001.psf” does not contain the instrument to supply these two values. The Multimeter window needs to be opened in dBV mode to do that."

Really, I don't understand where are they in the dtp file. If I open the \psf\RTX6001\IMD_SMPTE_60Hz(4)_7kHz(1)_FFT65536_RTX6001.psf and inside this open the multimeter and the DDP Viewer with RMSDBV_A(dBEU), RMSDBV_B(dBEU) data, the multimeter shows only the frequency and the DDP data nothing.
Is it right to include this as Derived Data Point to dtp file?

[VirtinsTech]

1) Step 6: X3= 0.000000316228 (V) specifies the initial output level. To start with 40dB higher, let X3=0.0000316228 (V) instead. Assuming RTX6001 is used as the DAC, then 0dBFS would be 14.14V. If you want to start right at -100dBFS, then let X3=0.0001414 (V) at this step.

2)
- There will always be some small "artefact" at the points where the input or output range is switched.

- Yes, you are right. In this DTP, the input auto ranging is done by the algorithm inside the DTP while the output auto ranging is performed automatically by MI based on the setting at [Setting]>[DAC Device]>"AutoRanging". By default, the output autoranging threshold is set to 0dBFS. You can change it to -3dBFS for better output distortion performance.

- This DTP is originally designed to test an unknow DAC using RTX6001 as the ADC only. Therefore, the 0dBFS output level (uncalibrated) is assumed to be 1V. If you use RTX6001 as the DAC instead, then the 0dBFS output level should be 14.14V, and the following changes need to be done:

1. At Step 20, change "X3<1" to "X3<14.14"
2. at Step 22, Change "X3=1" to "X3=14.14" (This step is not absolutely necessary. It is simply to make sure that the last X-Y point is tested right at 0dBFS.)

3) The -3dB threshold value for input and output auto ranging may not be the optimum one. You may do some experiments to find a better one.

[VirtinsTech]

- x2 variable has removed and I don't know what is the role of it for 2x to Ch.B, perhaps it was still from initial dtp file that I had modified (thd, thd+N vs Magnitude).

X2 is used for Ch. B Input Range. The input ranges of the two channels can be set independently via x1 and x2.

Really, I don't understand where are they in the dtp file. If I open the \psf\RTX6001\IMD_SMPTE_60Hz(4)_7kHz(1)_FFT65536_RTX6001.psf and inside this open the multimeter and the DDP Viewer with RMSDBV_A(dBEU), RMSDBV_B(dBEU) data, the multimeter shows only the frequency and the DDP data nothing.
Is it right to include this as Derived Data Point to dtp file?

RMSDBV_A(dBEU) and RMSDBV_B(dBEU) are among the data to be captured in your very first DTP. They are not of interest here and thus have been deleted in subsequent DTPs.

Click anywhere within the Multimeter window, you can select its type (e.g. frequency counter, dBV, dBu, etc.) in the middle selection box at the bottom of the screen. Anyway, it is not used here.

[lemon]

Thank you a lot for all these information.

I spent time to experiments to various combinations btw ADC-DAC Output and Peak Level Check.
The best that I achieved was the first capture.
Then I followed a simple method, like case-2.
I make 4 .psf files at the levels of -20/0/+20/+30 dBV with 131K IMD-SMPTE and Intra-Frame Proc. Linear 5.
After some experiments, that gives me better result, I make the capture-2.
I know it isn't perfect but it is closed to real...see the capture-3 from a manual measurement.

[lemon]

Here is the .dtp file