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DG4000 - a firmware investigation
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RoGeorge:
I see no reason why it should jump like that.  Maybe the calibration instruments are not calibrated, or maybe the measuring setup has something wrong in it, maybe a cable is faulty, IDK, but my unlocked DG4102 doesn't show any amplitude jumps in the first 30MHz or so (also never touched its calibration - I suspect the altered calibration might be the most probable cause for seeing jumps).

Does the amplitudes and frequencies of the jumps preserve when a narrower frequency sweep is performed?
ralphrmartin:
It's the voltage settings (not RF power settings) which caused the jumps, and that was done with a 6.5 digit Agilent meter I've no reason to suspect to be out of spec. BNC coax lead to a BNC-banana plug splitter. Same coax lead to BNC-to-N adapter for spectrum analyzer. No problems with these leads etc in other work.

I've tried calibrating twice now, and both times ended up with jumps, once before going back to firmware 08 and redoing things there, and once after coming back to the latest fw.

Note that my machine doesn't show any jumps if you reset to the factory calibration.

Maybe the calibration procedure itself has some issues. It would be interesting to know if anyone has successfully recalibrated their DG4000 with the procedure given, with the current fw.
RoGeorge:
Does the same Agilent voltmeter shows the generated voltage (after calibration) as correct (constant) when tested at various fixed frequencies?  If not, then the calibration procedure went wrong.  If yes, then it's either the voltmeter or the spectrum analyzer.

Voltage jumps of 3 or 6 dB should be easy to spot on any instrument.  Does the jumps show on other instruments, too, e.g. an oscilloscope or some other less precise voltmeter?
ralphrmartin:
Thanks for your comment, RoGeorge.


--- Quote from: RoGeorge on October 27, 2020, 05:51:39 pm ---Does the same Agilent voltmeter shows the generated voltage (after calibration) as correct (constant) when tested at various fixed frequencies? If not, then the calibration procedure went wrong.

--- End quote ---

True (as long as I use frequencies within the meter's AC range), but that doesn't tell us where it went wrong:
- voltmeter not working correctly (e.g. giving inconsistent readings at different frequencies)
- I misapplied the calibration procedure (failed to write some values, entered incorrect values by mistyping for example)
- there's a bug in the user calibration procedure code e.g. it
-- tries to measure voltages at frequencies outside the DMMs capabilities
-- does something wrong with the entered values (stores them in the wrong place, wrong format, etc)


--- Quote from: RoGeorge on October 27, 2020, 05:51:39 pm ---If yes, then it's either the voltmeter or the spectrum analyzer.

--- End quote ---

Not necessarily. The software in the DG4000 in general, and the sweep function in particular, may make some assumptions about the calibration. It is certainly doing something strange when sweeping, as the jumps may or may not be present depending on exactly what frequency range you sweep. Intuitively, miscalibration should always lead to the same voltage at the same frequency, just the wrong voltage, and that is not happens. The voltage you get at a particular frequency depends on the frequency range of the sweep.

Unfortunately, because of the jumps, I reset it to the factory calibration (which doesn't have them), so I have now way of telling which of these possibilities it is, without wasting another 1/2 day to redo the calibration. Note that lack of jumps observed with the factory calibration indicates that the jumps are real in my calibration (you said to see if they exist using a different instrument).

Furthermore, the factory calibration does give readings on the voltmeter (using the same leads) from 1kHz to 100kHz (in steps of 1kHz) which are within 0.2% or better of the stated output of the DG4000, so I have no reason to think the voltmeter is playing up.

Perhaps the software makes some assumptions about the entered calibration values, and if the calibration values entered are too far from the expected ones, it breaks these assumptions
ZETOR1:
Hello. I have dg4062 software version: 00.01.01. I want to update to 00.01.06. Where I can find 01.01.06. or 00.01.07?
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