1104x-e and ESD(?) - Page 1
Forum section: electronics / beginners

author: Sendi
author_rank: Newbie
timestamp: December 28, 2022, 10:15:32 pm
content: Hello,recently i bought siglent 1104x-e and i noticed that it sometimes restarts for example whenI plug cable into usb-b socket (device mode) even if other end of cable is unpluggedWhen i plug that cable to the pcWhen i touch any metal (ground) part on the scope and there is a plug in USB-B socketWhen nothing is plugged to the USB-B socket and i touch metal pendrive plugged to the back usb portAlso sometimes if i touch metal pendrive plugged to front usb it semi-crashes - usb stops working and I cant turn off scope with button but it reacts to other buttons and knobs.Touching doesnt even have to be by hand, its triggered sometimes by multimeter probe. I also tried few usb cables with same resultsBeside that scope seems to work fine.What i want to know is if this is faulty device or is it just lack of esd protection on my side.I mean i was using Rigol 1054Z in the past and didnt have any problems like that. That makes me think this new scope is too sensitive.Thanks for helping

author: BillyO
author_rank: Super Contributor
timestamp: December 28, 2022, 10:20:12 pm
content: Sounds like a grounding issue. Have you checked the grounds going to the scope and the PC?

author: Sendi
author_rank: Newbie
timestamp: December 28, 2022, 10:29:58 pm
content: PC is grounded and scope was tested both with and without earth. But situation with PC connected is only one of several others that problem appears

author: BillyO
author_rank: Super Contributor
timestamp: December 28, 2022, 10:37:52 pm
content: Both my Siglent scopes are rock solid. How new is this and where di you buy it?

author: Sendi
author_rank: Newbie
timestamp: December 28, 2022, 10:44:29 pm
content: In Poland from "authorized distributor".FPGA version 2021-11-08,Hardware version 09-06.It was calibrated in 12.2021

author: BillyO
author_rank: Super Contributor
timestamp: December 28, 2022, 10:56:47 pm
content: I would contact the distributor. Siglent have a 30 day return policy so if they are an authorized distributor, they should honor that.Have you installed the latest firmware?

author: Sendi
author_rank: Newbie
timestamp: December 29, 2022, 09:52:53 pm
content: Yes I did. Nothing changed

author: wraper
author_rank: Unknown
timestamp: December 29, 2022, 09:57:12 pm
content: Quote from: BillyO on December 28, 2022, 10:20:12 pmGround is for safety, nothing to do with ESD immunity. I would return the scope if possible since it seems to be marginally working.

author: BillyO
author_rank: Super Contributor
timestamp: December 29, 2022, 11:02:31 pm
content: Quote from: wraper on December 29, 2022, 09:57:12 pmThink about what I said. Think about the situation. Think about the leakage current that can (will) develop when an ungrounded device with a SMPS is connected via a communications cable to a grounded device. Unlike linear supplies with transformers, SMPS can generate fairly high voltages WRT earth/ground. These voltages can manifest anywhere in the ungrounded device with an SMPS, especially in the output voltages of the supply. These are then used to power all components of the device, including the USB chips. So, when a floating device is connected to a grounded device via a USB cable, strange things can, and do, happen.In other words, his problem mightNOTbe ESD. It might be improper grounding.Proper grounding isNOTjust for safety. Next time, just think.Oh, and if you think grounding a large floating piece of equipment like a scope though a flimsy USB cable though a computer will not make it more ESD sensitive, you need to give you head a shake. But thanks for your input.

author: wraper
author_rank: Unknown
timestamp: December 30, 2022, 07:40:45 am
content: First of all earth wire has too much of length and induction to offer protection against ESD as it causes extremely fast impulse (nanoseconds). Secondly usual ESD discharge to scope ground must not cause malfunction if device is not faulty.QuoteSMPS more likely to have Y interference suppression caps between primary and earth which causes more current leakage. However it has nothing to do with device rebooting if not faulty. Again, earth wire is for safety only, devices without earth connection require stronger insulation from mains voltage. There could be an argument if reboot happens only when plugging USB cable but it's not only that.QuoteLack of earth connection may be a contributor but not the root cause. In case of the scope the major risk is damaging a circuit which you measure due to half of mains potential on earth alligator clip due to discharging Y interference suppression capacitors into a circuit. If scope is not faulty, lacking earth connection should not cause device malfunction. Normally it has no way to impact internal circuit of the scope. The only way scope can reboot on occasional ESD event of not too high energy is if it's already marginally stable and reasonably small electromagnetic disturbance sends it into reboot.The only thing I suspect without scope being faulty is an out of spec USB cable with no shield or some connection lacking, or USB port with no proper GND connection (either on scope or PC side) which causes extreme voltages going into data lines which causes CPU malfunction and watchdog resetting the scope.