Whish list

Whish list

Postby RJA4000 » Sun Oct 17, 2021 4:20 pm

As you know, I'm using MultiInstrument to automate audio measurements.

There are a few things I whish would be available

1. In ADC, you have a choice of channel operations
To increase ADC SNR, I usually select A=(iA+iB)/2
With RME ADI-2 Pro fs, I just use the M/S option (L = (iL+iR)/2, R = (iL-iR)/2)
but with new ADC I'm using, this option is not available.

So could you please add [A=(iA+iB)/2] as an option in the ADC channel operations ?
Actually, we could see 3 additional options:
A=(iA+iB)/2, B=(iA-iB)/2
A=(iA+iB)/2, B=iB
A=iA, B=(iA+iB)/2

2. REW is using Blackman Harris 7 FFT window type
To facilitate comparison with others' measurements, it would be great to have that FFT window type in the list, if possible.
EDIT: I see it is available. On my main (Full HD) monitor though, the list ends with Kaiser19. Only on my secundary monitor (UHD) I see the remaining ones.
I would also like to have something that is close to the default AP-Equiripple for AudioPrecision.
They list it as "an approximation to the Dolph-Chebyshev window". They also have Dolph-Chebyshev 150,200 a,d 250.

3. My automation includes some Digital Multimeter measurements.
Would it be possible to automate WRITING a value to a UDDP ?
Then we could use the same PSF file and adapt it with proper calibration values programmaticaly.

4. DPP display is a bit erratic in terms of format
Would that be possible to set the font size and color, and to set text alignment (right, middle) ?
And also to allow selection of multiple DPP windows and then to align position / size (left, top, bottom, right, width, height) from a contextual menu ?
That would greatly improve the look of the window

5. I don't know if that's feasible, but programmaticaly, we can save the FFT plot as a csv file and the input wave
Is it possible to allow that from a menu as well ?

6. I still really whish we could at least read the PSF file, to allow identifying the differences, at least.
Ideally, I'd like to write them too, but...

7. 32 bits PCM format support would be welcome

8. I don't calibrate the level in MI. So in signal generator, I use 1V = 100% and 0.5V as 50%
Would it be possible to (optionnaly) enter directly the Amplitude in dBFS and to then change the UoM to dBFS if that option is active ?
That would save me a lot of external computing.
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Re: Whish list

Postby MRH » Thu Oct 21, 2021 6:21 am

* It would be great if the UoM dBFS was available for all measurements (generator and input).
* Being able to do CHK comparisons using dBFS and relative dB units would be very useful.
* Within DTP the use of the generic term "V" isn't intuitive (easily mistaken for RMS etc). As used currently, 'Vpk' would be better.
* Signal generator output in dBFS would be very helpful (sticky units - that don't drop back to 'V' would be great here).
Thank you so much!
VPK.png (2.3 KiB) Viewed 3269 times
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Re: Whish list

Postby VirtinsTech » Tue Oct 26, 2021 4:00 am


Thanks a lot for all the suggestions!

1. Will be implemented in the coming new version V3.9.5.


(1) The vertical scrollbar for selection from a long list of window functions is somehow missing under some screen resolutions. This issue will be fixed in the coming new version.

(2) AP-Equiripple window function is a proprietary Audio Precision window function. The information on how to construct it is not available publicly. Nevertheless, it should not be a limitation without it, as MI has a lot more window functions available for various applications.

(3) Dolph-Chebyshev window functions are constructed from frequency domain unlike other window functions, and thus inverse FFT or DFT is required to derive the time domain data. The problem is that FFT is fast but DFT is super slow. In MI, inverse DFT has to be used in the Spectrum Analyzer when zero-padding is required, and window-based FIR digital filter design in the Oscilloscope and window-shaped masking (gating) in the Signal Generator when the window size is not a power of 2. Due to this reason, Dolph-Chebyshev window functions were not included in the software previously. They will be included in the coming new version, with the speed issue with a large window size being highlighted in the software manual.

3. If you use Device Test Plan for your automation, then there are volatile integers: VolatileInt1~ VolatileInt5, non-volatile integers: NonVolatileInt1~ NonVolatileInt5, and volatile floating-point variables: x1~x5 available for use. They can be mathematically operated with DDP and UDDP (for example, using the OPT instruction). Would that work for your cases?

You can also use ActiveX Automation API for your automation. It provides much more flexibility.

(1) The software already uses a fixed-width font for text display. So seven-segment display or font selection may not be necessary.

(2) For channel-specific DDPs, the text color is determined by the color of the channel. For those cross-channel DDPs and channel-irrelevant DDPs, "Other Text color" is used. These colors can be configured via [Setting]>[Display].

(3) The number of characters displayed in a DDP viewer may vary with time. To save screen space, the software does not display a fixed number of characters. Otherwise, the DDP viewer window would have to be made wide enough to allow for the maximum possible number of characters, which would leave a big empty space on the left side for most of the time. Instead, the software adjust the font size dynamically to accommodate the required number of characters. Thus the display may look erratic temporarily when the number of characters changes. The software has a mechanism in place to prevent changing the font size back and forth frequently. So sometime the DDP viewer leaves an empty space on its left side temporarily.

(4) The software allows for automatic re-arranging all windows via [Window]>[Tile Horizontally] or [Tile Vertically].

(1) The data in every graph windows in MI can be saved as a CSV text files. Just right click the window, and select "...Copy As Text" (into Windows Clipboard and then paste it out into other text editors) or "... Export" to a CSV text file.

(2) The CSV text file exported from the Oscilloscope, Spectrum Analyzer (auto correlation, cross-correlation, and impulse response), Signal Generator can be loaded into MI for analysis via [File]>[Import].

6. This is a difficult task. There are at least a few thousands of interlocked parameters inside a PSF file. Also, it contains version control information so that old PSFs can be used in later version of the software. Moreover, we do not see much use of the function requested.

7. This will be implemented in a future version. Most likely, the one after the coming new version.

8. The full-scale ranges of ADC and DAC are always specified in peak values. That is why peak values are used in MI's Signal Generator so that it will not exceed the DAC full-scale range. Peak values are more intuitive than RMS values when constructing a waveform. Only when the crest factor of the waveform is known can RMS values be derived. This is not a problem for a continuous sinewave or square wave, but it is a problem for white noise, pink noise, multitones, bursts, impulses and arbitrary waveforms. Therefore, peak values should always be used in the Signal Generator.

On the other hand, dBFS, dBu, dBV values normally refer to RMS values, not peak values. Moreover, for RMS in dBFS, there are two conventions available for 0 dBFS reference: FS sinewave (AES standard) and FS square wave. They are both available in the MI's Spectrum Analyzer Y Scale options.

Thus, in the Signal Generator, the peak value in Voltage is still the primary parameter for amplitude in order to eliminate any confusion (peak vs RMS, 0 dBFS reference). dBFS, dBV, dBu are still displayed, but only for reference, and keep in mind that they refer to peak values in the Signal Generator. For example, a 0 dBFS (peak) sinewave will have a RMS amplitude of 0 dBFS in the Spectrum Analyzer (ref: FS sinewave), but a 0 dBFS (peak) square wave will have a RMS amplitude of 3.01 dBFS in the Spectrum Analyzer (ref: FS sinewave).

Having said the above, you can still adjust both voltage and dBFS simultaneously by dragging the scrollbar beside.
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Re: Whish list

Postby VirtinsTech » Tue Oct 26, 2021 4:13 am


Thanks a lot for your suggestions!

1. Please refer to Item 8 above. Also, dBFS is available in the Spectrum Analyzer for various RMS values.

2. dBFS, dBr, dB, dBV and dBu can be used in CHK instruction in Device Test Plan. When you change the Spectrum Analyzer Y Scale, the relevant DDPs will change accordingly.

3. Will be changed in the coming new version, probably change to "Vp" instead of "Vpk" to save some screen space.

4. Please refer to Item 8 above.
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Re: Whish list

Postby MRH » Tue Oct 26, 2021 5:15 am

Excellent, thanks!
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Re: Whish list

Postby RJA4000 » Sun Oct 31, 2021 9:12 pm


Thanks for your feedback
Much appreciated !

3. I use .Net programming, not Device Test Plan
My .Net program also gets data from outside MultiInstrument:
From my Digital MultiMeter and from a database of device tests

When a measurement is done, I like to save a screen copy, to publish the screenshot with the device test.
For that, it would be helpful if I could, as requested, programmaticaly enter a value in a UDDP.
I now do it manually, but this is then very slow.

There are also measurements where the final result relies on the current measurement AND values from a previous measurement.
An Example is EIN noise, where you first need to measure the DUT gain accurately, then the noise for that gain.

4. (4)
The software automatic re-arrangement is screwing my own arrangement.
As an example, I build this type of screen. I'd like to have a way to align the UDDP boxes as requested.
2021-10-31-13_43_26-Greenshot_.jpg (156.14 KiB) Viewed 3038 times

(You also see in this example a UDDP I'd like to write to in the bottom right.)

5. I just realized you need to stop data capture to allow saving.
OK, it works.

6. When building PSF files for complex and multiple text scenario, it would be usefull to at least be able to compare 2 PSF files, to check for differences.

8. I realized the full range is in Vpk by experience
This is indeed great, it makes 100% sense.

But I have 2 comments

a. In signal Generator, "V" unit is confusing when I build above dashboard, since the amplitude, in my case, is not correlated to the "V" value.
Having a choice to use "%" would already be better

b. You have a UDDP called "Output Amplitude", which measures in dBFS
Also, the vertical Amplitude slider value is labbeled as "dBFS"
So why not to be able to enter directly this ? (With a warning, if needed)

c. One may indeed use the vertical sliders.
I just realized I could use up and down arrows to move them by 0.1dB

Thanks again for all your great work here :-)
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Re: Whish list

Postby RJA4000 » Sun Oct 31, 2021 9:20 pm

Another question, by the way:

In the example I posted above, you can see that Distortion phases are not displayed.
This seems to be always the case when you perform an inter-frame average.

Is that on purpose or would that be possible to fix that ?
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Re: Whish list

Postby RJA4000 » Fri Nov 05, 2021 10:35 pm

Still another (few) request:

9. I think it would be good to get a DDP for "Crest factor" for each channel
"Crest factor" being [Peak V]/[RMS V]
Could be measured in dB as well (that would be 4 additional DDPs then)

10. Also, I'm interested in a delay (in ms) measurement DDP between channels

11. dBr level: Would that be possible to set the reference frequency ?
As an example: 1kHz is the reference level
Then dBr may be positive (above the 1kH level) or negative...
Would be useful for frequency response.


OK, I know, I have a lot of imagination...
All based on real life experience though.
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Re: Whish list

Postby VirtinsTech » Thu Nov 25, 2021 2:21 am


Thank you for all your suggestions and explanations, and sorry for the late reply, as we want to figure out the solutions or even finish the relevent development first before we commit them here ;) .

3. SetUDDP(LPCTSTR sUDDPName,double dValue) will be added in the Automation API to allow the Automation client program to set a UDDP value in Multi-Instrument. This function will be available in the coming new version.

4.(4) Some improvement could be done in the future.

6. You can compare the parameters in two PSF files manually using two instances of Multi-Instrument.

8. a. As the default and non-calibrated peak output voltage is 1V, you can simply consider it as 100%, then 1% <->0.01V, which is quite intuitive.
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Re: Whish list

Postby VirtinsTech » Thu Nov 25, 2021 3:30 am

RJA4000 wrote:Another question, by the way:

In the example I posted above, you can see that Distortion phases are not displayed.
This seems to be always the case when you perform an inter-frame average.

Is that on purpose or would that be possible to fix that ?

The measured phase in Multi-Instrument refers to the initial phase (i.e. the phase of the leftmost sample of an Oscilloscope data frame) of a sine function. In the current version, the phase information will not be available under either of the following conditions:

(1) when Intra-frame averaging or zero-padding is performed automatically by the software

a. When [Record Length] < [FFT Size], zeros will be padded at the end of the data frame automatically, no phase information will be provided.

b. When [FFT Size]<=[Record Length]< (2 x [FFT Size]), no zero padding and no intra-frame averaging, thus phase information will be available.

c. When [Record Length] >= (2 x [FFT Size]), intra-frame averaging will be performed automatically, phase information will be lost.

(2) when Inter-frame averaging is performed and the averaging with the second data frame has been done.

Phase information will only be available for the very first data frame. This is because there is no guarantee that the second data frame and those after will have the same initial phase, depending on the trigger setting and the ratio of [Sampling Rate] to [Signal Frequency], etc. Therefore, averaging on phase may not improve the phase measurement accuracy.

In the coming new version, the limitation of the above (1)a and (1)c will be removed. (2) will be modified to make the phase information of the very first data frame available during the whole process of inter-frame averaging.
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