SIGLENT SDM: VMC OUT madness - Page 1
Forum section: electronics / testgear

author: uliano
author_rank: Regular Contributor
timestamp: December 14, 2024, 11:16:25 am
content: I'm trying to chain measurements between different instruments. the last part of this chain is made by a SDM3055 and a SDM3065 to measure respectively current and voltage.Here I'm only concerned with timings, I setup a burst of pulses that I fed into the 3055 trigger input, its VMC out is then fed into the trigger input of the 3065X all 3 signals (including VMC out of the 3065) are recorded by the scope.In the manuals VMC OUT is described to go off AFTER the measure has been completed. My experience is that it goes off after some preliminary stuff and BEFORE the actual measurement (aperture) happenshow can I say so? by looking at scope traces it is quite easy to deduce it. Moreover the position of the VMC out signals does not depend on aperture duration.the two instruments have been set up by software and the parameters on the display correspond to the programmed setting. Here it is the relevant part of the setupCode:class Voltmeter(SDM):def __init__(self, **kwargs):super().__init__('192.168.1.9', **kwargs)def setup(self, n=10, nplc=0.5, delay=0.0):self.write(':*RST')self.write(':CONF:VOLT:DC')self.write(':VOLT:DC:RANG 20')self.write(f':VOLT:DC:NPLC {nplc}')self.write(f':TRIG:COUN {n}')self.write(f':TRIG:DEL {delay}')self.write(':OUTP:TRIG:SLOP POS')self.write(':TRIG:SOUR EXT')self.write(':TRIG:SLOP POS')self.write(':SENS:VOLT:DC:AZ OFF')self.write(':SENS:VOLT:DC:NULL OFF')def init(self):self.write(':INIT')class Ammeter(SDM):def __init__(self, **kwargs):super().__init__('192.168.1.5', **kwargs)def setup(self, n=10, nplc=0.3, delay=0.0):self.write(':*RST')self.write(':CONF:CURR:DC')self.write(':CURR:DC:RANG 200mA')self.write(f':CURR:DC:NPLC {nplc}')self.write(f':TRIG:COUN {n}')self.write(f':TRIG:DEL {delay}')self.write(':OUTP:TRIG:SLOP POS')self.write(':TRIG:SOUR EXT')self.write(':TRIG:SLOP POS')def init(self):self.write(':INIT')voltmeter = Voltmeter()voltmeter.write('*RST')voltmeter.setup(nplc=10)ammeter = Ammeter()ammeter.write('*RST')ammeter.setup(nplc=10)voltmeter.init()ammeter.init()scope.single()trigger.start()Has anyone been successful in getting VMC out signal AFTER the aperture time?

author: uliano
author_rank: Regular Contributor
timestamp: December 14, 2024, 11:22:27 am
content: Another question, secondary at the moment, is why 3065X is much slower to react than 3055 and if there are settings to reduce the "dead" time

author: tautech
author_rank: Super Contributor
timestamp: December 14, 2024, 12:27:36 pm
content: Quote from: uliano on December 14, 2024, 11:22:27 amOne cannot know without knowledge of the firmware versions in use.Have you checked if there anything to help on this topic in the App notes or Operating tips ?https://www.siglenteu.com/application-notes/digital-multimeters/https://www.siglenteu.com/operating-tips/digital-multimeters/

author: uliano
author_rank: Regular Contributor
timestamp: December 14, 2024, 01:15:52 pm
content: voltmeter = Voltmeter()print(voltmeter.query('*IDN?'))ammeter = Ammeter()print(ammeter.query('*IDN?'))Siglent Technologies,SDM3065X,SDM36HCC800197,3.02.01.13Siglent Technologies,SDM3055,SDM35GBQ5R1758,1.02.01.28last should be the firmware version. The 3065X is newer that what is available on download page I suppose because it's a recent unit, bought it a few weeks ago.Yes, I checked everywhere and I always found mention of VMC OUT issued AFTER the measurement aperture.

author: tautech
author_rank: Super Contributor
timestamp: December 14, 2024, 01:35:22 pm
content: No answers in the Programming guide ?https://www.siglenteu.com/wp-content/uploads/dlm_uploads/2017/10/SDM-Series-Digital-Multimeter_ProgrammingGuide_EN02A.pdf

author: uliano
author_rank: Regular Contributor
timestamp: December 14, 2024, 02:39:15 pm
content: It is coherent with all other information I gathered (see attachment) . Here I'm confronting 2 really unlikely possibilities:1. I have 2 units (of different model) that are both broken in the same very specific way2. I'm the first human in the whole universe that attempted to use the VMC OUT signal and for this very specific reason nobody reported the firmware bug to Siglent (neither they tested the function by themselves)I simply can't believe both, that the reason for choosing "madness" in the topic.As this signal is reported everywhere to do only the same thing -> emitting a pulse after the measure <- and as it does the opposite on two different instrument model I'm convinced that there is no point in searching for esoteric procedure to make it behave. it definitely should be either 1 or 2.:'(

author: uliano
author_rank: Regular Contributor
timestamp: December 14, 2024, 03:39:13 pm
content: As for SDM negative pulses are default, I tested also in this condition:same behaviour

author: uliano
author_rank: Regular Contributor
timestamp: December 14, 2024, 05:22:52 pm
content: Now I have a doubt, while in programming manual mention is made to “measurement complete” in user manual the wording is “sampling complete”.May it be that measurement aperture is made after sampling has completed? If this is the case the early VMC pulse has some sense: “now you may set next condition” but what I don’t understand is if sampling is complete why care for integral multiples of NPLC? Why call “aperture” a time period in which the input port is already closed?More and more confused

author: KungFuJosh
author_rank: Super Contributor
timestamp: December 14, 2024, 05:38:26 pm
content: I don't know anything about the programming thing you're trying to do, but I do know that:1. Don't hold too much weight on any semantics in the manual. The manual is probably not written in English first. There will be a language barrier going back and forth, and probably worse if it has to be translated to another language later.2. If you think the speed of the readings coming from the SDM3065X are too slow, then your NPLC number is too high. Lowering that will give you faster readings.

author: 2N3055
author_rank: Super Contributor
timestamp: December 14, 2024, 08:05:34 pm
content: 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.

author: uliano
author_rank: Regular Contributor
timestamp: December 14, 2024, 09:38:13 pm
content: Quote from: 2N3055 on December 14, 2024, 08:05:34 pmif 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)

author: 2N3055
author_rank: Super Contributor
timestamp: December 14, 2024, 09:59:19 pm
content: Quote from: uliano on December 14, 2024, 09:38:13 pmAre 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.

author: uliano
author_rank: Regular Contributor
timestamp: December 15, 2024, 02:13:45 pm
content: 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/misleadingHow 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 gibberishSecond 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) there is no acknowlegment of the contact by mail. Just wait and hope the webiste didn't redirect it to /dev/null

author: uliano
author_rank: Regular Contributor
timestamp: December 16, 2024, 01:00:19 pm
content: Quote from: uliano on December 15, 2024, 02:13:45 pmSiglent 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