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SIGLENT SDM: VMC OUT madness

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uliano:

--- Quote from: 2N3055 on December 14, 2024, 08:05:34 pm ---I must say that your overly complicated setup is blocking me from understanding what is going on.

Just isolate one meter, say SDM3065.
Set NPLC and trigger settings manually on meter.
Don't set it up with SCPI.

Apply input pulses and measure that and VMC OUT with a scope.
Meter that responds with "measurement completed" signal sooner than you think it should might be just that meter is sampling with different NPLC than what you think you set.

When testing these type of things, test in isolation and one variable at a time. It is faster and simpler that way.

--- End quote ---

if you set by software or by keypresses the values are there and are the same, the delay between trigger in and VMC out are constant with EVERY setting of NPLC, this is coherent with the fact that VMC is issued before aperture time.

(setting by software saves you lots of time if you are making many tests and you can be repeatable)

2N3055:

--- Quote from: uliano on December 14, 2024, 09:38:13 pm ---
--- Quote from: 2N3055 on December 14, 2024, 08:05:34 pm ---I must say that your overly complicated setup is blocking me from understanding what is going on.

Just isolate one meter, say SDM3065.
Set NPLC and trigger settings manually on meter.
Don't set it up with SCPI.

Apply input pulses and measure that and VMC OUT with a scope.
Meter that responds with "measurement completed" signal sooner than you think it should might be just that meter is sampling with different NPLC than what you think you set.

When testing these type of things, test in isolation and one variable at a time. It is faster and simpler that way.

--- End quote ---

if you set by software or by keypresses the values are there and are the same, the delay between trigger in and VMC out are constant with EVERY setting of NPLC, this is coherent with the fact that VMC is issued before aperture time.

(setting by software saves you lots of time if you are making many tests and you can be repeatable)

--- End quote ---


Are values the same? Did you try what I said?
Of course setting with software saves time, but we are now troubleshooting.

Now you can have :

1. problems that code does not send proper data (not necessarily error of programmer)
2. problems that meter might not interpret SCPI commands properly (for various reasons)
3. fact that it is hard to understand what is really happening here.

If I understood correctly, your claim is :
"When I trigger acquisition with Trigger in, VMC Out pulse seem to get pulsed before end of acquisition should be by NPLC settings.
Also that (too short) delay between Trig IN and VMC Out does not change when changing NPLC".

Like I said, could you please simplify the setup, just one meter, and scope with only Trig in and VMC out and so we can see exactly what the delay is.
Then change NPLC on meter manually. Also make sure you are doing acquistion on Triggered input.

If you want to prove one thing you test for that exact thing.
Using only one meter and manual setting enables others that have that meter to check (like KungFuJosh for instance).
Nobody is going to replicate your setup, load software or whatever...
You need to help people to help you....

If this is problem with FW, people should be able to replicate same timing as you, down to µs.
Then we have a bug to report, and also a simple recreation procedure for Siglent.
If if it is not working right, they need to fix it.

uliano:
I think I got to the end of this "reverse feature".

The VMC Out is sent at the beginning of the aperture and not at the end and, as such, it is mostly useless/misleading  >:(

How I can be so sure?

New setup:

The trigger now comes from Trigger Out of  TTi SMU4201 (channel 1), at the end of its aperture and is fed into trigger input of both SDMs that are set up as a voltmeter to measure the same voltage as the SMU (across a resistor). I basically have 3 voltmeter connected to the same d.d.p.

As SDM3065 (channel3) is (much) slower in spitting VMC Out pulse it is its signal that is fed to the SMU that acknowledges it by setting low channel 1 and going on to the next level in the pulsed sweep.

Channel 2 is VMC Out of 3055.

First experiment setting aperure of both SDM as 1NPLC (20 ms in this side of the world) the scope traces c2 and c3 indicate when aperture begins respectively for 3055 and 3065x. all the voltage readings from the SDM are zeroish gibberish

Second experiment setting apertures at minimum values 0.3NPLC = 6ms for 3055 and 0.005NPLC = 100us for 3065x as detail screenshots show now there is enough time to have the aperture while the voltage is still high and it can be clearly seen that the reading done at the right timing now are identical to the SMU reading.

For me this is final.

I'm just so sad that I can't use my Siglents for this purpose and I quite can't believe that I'm the first to report such a bug. I contacted siglent through the webform and exactly as for TTi (they have their bugs too  |O ) there is no acknowlegment of the contact by mail. Just wait and hope the webiste didn't redirect it to /dev/null

uliano:

--- Quote from: uliano on December 15, 2024, 02:13:45 pm ---I'm just so sad that I can't use my Siglents for this purpose and I quite can't believe that I'm the first to report such a bug. I contacted siglent through the webform and exactly as for TTi (they have their bugs too  |O ) there is no acknowlegment of the contact by mail. Just wait and hope the webiste didn't redirect it to /dev/null

--- End quote ---

Siglent promptly answered (and that makes me happy as I have a lot of their stuff  :) ). They say they can have VMC Out delay from trigger according to the aperture setting so at the end it may really be I overlooked some required setting. I'm waiting for further developments

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