I am running the Power IMD tests. While the IMD ITU tests look fine, the IMD SMPTE right channel is skewed to the left (in output power). I ran the tests consecutively and multiple times. In the plots below, I gave the program an input range that would get me about 100mW to 130W of output power.
What is going on?
Also, Why does it say Input Power (Watts) at the bottom of the graph, when it is Output Power?
Hi @DaveD, I can confirm what you are seeing. A bugfix will be released tomorrow. Thanks very much for reporting and the extensive detail. BTW, the “Input Power (Watts)” on the X-axis is from the reference point of the analyzer. In other words, it’s what the analyzer is seeing. And when you see something like “Output Level” it’s also from the standpoint of the analyzer. I agree it can get confusing if you are in a DUT frame of mind. Maybe it should say Analyzer Input Power, but that suggests the Analyzer is soaking up the power which is wrong too.
It could be DUT Output Power, which probably makes the most sense. It breaks the convention a bit, but maybe the new convention might be “If the DUT isn’t mentioned, then it’s reference to the analyzer. But if the DUT is mentioned, it’s reference to the DUT”
What do you think? DUT Output Power for the default? Of course it can be changed in the graphing tool. But you are right, it’s confusing on first (and second and third…) look.
Hi @matt. I think making “DUT Output Power” by default is a good idea. It would make it much clearer to everyone what the X-axis indicates and also there is always the possibility to edit everything in the graphing tool
OK, that makes sense to me too. Release 1.214 is up that corrects the IMD bug reported by @DaveD. For 1.215, the X Axis Title in the PWR IMD will be changed too.
However, to be consistent you might want to change the “AMP IMD (ITU and SMPTE)” graph also. However, it at least says Analyzer Output Level which is DUT Input Level as shown below.
Another issue I have with these IMD tests is that they leave GEN2 active after completion of a test. If I do say an AMP THD VS FREQUENCY test after the IMD test, it will overload the analyzer after a bunch of clicking sounds and I get the overload popup. I have to manually turn off GEN2, so I can run the test. I guess the best way for any test using a single generator, is to turn off generator 2 before starting.
Hi @DaveD, there is a checkbox in Edit->Settings called “Restore State after Automated Test Run”
If that is checked, then the settings that remain from the last automated test run will persist. That is, if the test used GEN2 then GEN2 will remain on and at the last amplitude and frequency.
If that is unchecked, then the settings you had before the automated test is run will be restored.
Can you make sure that box is checked and see if that fixes the issue you are seeing with the GEN2?
And yes, before you run an automated test you need to make sure there’s some sanity in the manual measurement. If the manual measurement isn’t making sense for whatever reason, the automated test might not make sense.
