Hi @matt. I wanted to report a problem I found in using the “PWR IMD (ITU and SMPTE) plugin. The problem occurs when choosing the “ITU” option, while with the “SMPTE” option everything runs smoothly. These are the “Start Level dBV” and “Stop Level dBV” fields in “PwmrImd Options.” These fields define (at least I think so, but maybe I am wrong) the value of Gen1 and Gen2 at the first step and the last step, respectively. When I select the “SMPTE” option, Gen1 assumes the value given in “Start Level dBV" at the first step and the ‘Stop Level dBV’ value at the last step, while Gen2 assumes the same values, but decreased by 12 dBV (4:1 ratio) as provided by the SMPTE mode. And here everything is working smoothly. The problem arises when I select “ITU.” In this mode the amplitude of the two generators is equal and the first step should be “Start level in dBV” while the last step should be “Stop Level in dBV.” Instead this does not happen to me: the 2 levels do not match what is specified in the two fields. I attach 2 screenshots: in the first one you can see the setting given by the 2 levels, in the second one you can see the value of Gen1 and Gen2 at the last step where you can see that it does not coincide with what is specified in the option field (obviously also the first step does not coincide with “Start level in dBV” although in the screenshot you cannot see it, of course). All this happens even if I run the plugin in a QA403 loopback connection. It is probably me making some mistakes.
EDIT: Or perhaps it could be interpreted like this (as John says): since in the ITU mode the two generators must provide the same amplitude, combining the 2 values results in a lower 3dB adjustment of the generators to achieve the value specified in “start and stop level.”In this way, the math would add up. But this rule would not seem to apply in the SMTPE mode
Hi, here is a screenshot of the “tool tips” related to “Start level dbV” and “Stop Level dBV”. They refer to the start and stop values of the outputs (ADC) of QA403, and this corresponds if “SMPTE” option is selected. While they are not verified with the ITU option. Of course, I could be wrong and maybe you are right.
EDIT: Or perhaps it could be interpreted like this (as John says): since in the ITU mode the two generators must provide the same amplitude, combining the 2 values results in a lower 3dB adjustment of the generators to achieve the value specified in “start and stop level.”In this way, the math would add up. But this rule would not seem to apply in the SMTPE mode
Hi Claudio, yes, @restorer-john has it right. If you set GEN1 to 19k and GEN2 to 20k, both at 0 dBV, and open up the RMS bandwidth to 21 kHz (to include all of the GEN2), then you should measure 3.01 dB total RMS. And so, the signals are set to -3.01 below your specified level. That gives an RMS that you specify.
For the SMPTE, it’s a bit different because you specify the level of the 60 Hz, and that gives you the level of the 7k (4:1 ratio = -12 dB). And then you measure the products relative to the 7k (not the 60 Hz).
Thanks Matt. This all clarifies the different setting of the genearators in ITU and SMPTE modes. This information is very useful for properly setting up the Excel sheet that calculates the values to be entered into the plugin setup to obtain the desired power values. Using the plugin I have encountered an apparent anomaly in operation that I cannot explain. In SMPTE mode when in the “Stop Level dBV” field I indicate a value less than -8dBV (and specific “increment dB =1”) everything goes smoothly and when the plugin is stopped, as expected, Gen1 indicates the value set in “Stop Level dBV”. If, on the other hand, I indicate in that field a value greater than -8 dBV (e.g., -7dBV) everything proceeds smoothly, but if I indicate as the first digit after the comma a “2” or a “7” ( e.g., -7.2 dBV or 7.7 dBV) when the plugin is shut down Gen1 does not indicate what was entered in “Stop Level dBV” but a value less than 1 “increment dB” . Perhaps the screenshots clarify better. Matt, when time permits, can you provide clarification on what I am doing wrong? Thank you for your patience
Hi @Claudio, yes, I see this too. I think this could be called the “endpoint problem” where the endpoint you specify for amplitudes and freqs wasn’t always hit. In your case above, it might be a floating point rounding issue, where if you add 1.0 to a floating point number often enough, the last point is missed because it’s outside the limits. But just by a very tiny amount…maybe 1x10-9 or so.
In release 1.215, you can see the release note comment that says "four automated tests have been moved to use centralized services. and then more in the notes on changes for Automated Tests. Now, the notes go into a lot of detail, but they don’t help the user very much understand a seemingly simple task! Which is “Why isn’t my endpoint respected!”
For the next release, let me make sure that all the tests get updated to use the same code paths and I think the issue you have discovered above will get fixed.
Thanks very much for reporting this! It will get fixed very soon.
Thanks Matt for the quick response. I use an Excel spreadsheet to calculate the values to enter in plugins where there is an automatic test depending on the power of the DUT. I “went crazy” to figure out what was happening: sometimes the power target, for no apparent reason, was not reached. Then, once I found out what was causing it, it was easy to make sure that the first digit after the decimal point was neither “2” nor “7” (solving the problem with this trick). If then in the next relise, even in the other plugins it will be possible to specify as inputs the minimum and maximum power desired at the output of the DUT, everything would be wonderful!
Thanks again
