Digital scope underwater - Page 1
Forum section: electronics / testgear

author: boumboauto
author_rank: Contributor
timestamp: January 13, 2018, 01:22:03 pm
content: Hello,I'm working on a projet to monitor voltages in an underwater enclosure. Once in the water the only links I have are Ethernet and 230V.I was looking at different options, oscilloscopes with an LXI port like the Rigol DS1054Z, oscilloscopes like the Keysight DSO60x0L series.The measurements to be made are to look at the output of a 4 quadrant inverter and see if overvoltage may appear. The PWM output is at 8kHz but I'd like to have 100Mhz per channel to see fast transients.Would you recommend using the 400$ option with the Rigol, or the 15000$ option with the Keysight ?The constraint is that I will not be able to physocally access the scope once it's in the underwater enclosure.I wonder why the Keysight is so expensive regarding to its specs.David

author: Yansi
author_rank: Super Contributor
timestamp: January 13, 2018, 01:36:59 pm
content: So the whole 1054Z will be in the water too or what ? Your intention is not that clear. You even haven't stated if you need all those 4 channels.

author: tggzzz
author_rank: Super Contributor
timestamp: January 13, 2018, 02:02:28 pm
content: Inverter.Overvoltage.Water. (Inverter must be submersed for the question to make sense).Someone in water looking at scope.What couldpossiblygo wrong?

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: January 13, 2018, 02:19:10 pm
content: Get one of these:https://www.ebay.com/itm/122344488818, looks quite water-proof-ish

author: 0xfede
author_rank: Regular Contributor
timestamp: January 13, 2018, 02:50:51 pm
content: Quote from: tggzzz on January 13, 2018, 02:02:28 pmIt could rain

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 13, 2018, 04:03:20 pm
content: The R&S RTB2000 has a very good and fast remote web interface over gbit ethernet, pretty much like having the scope in front of you.Though for something like this you may want to use something cheap in case of leaks....Minor issue with some recent scopes is they have a soft on-off button, so may not be able to reset remotely by power cycling if something goes wrong. The RTB2000doesremember its soft on/off state so can be remotely power cycled.Another option may be a USB scope with a USB-ethernet converter, e.g. the Owon VDS3104. They do show a version with inbuilt ethernet but not sure if this is actually available or implemented - the USB one is pretty decent.

author: Bud
author_rank: Super Contributor
timestamp: January 13, 2018, 04:20:10 pm
content: Sorry, how airflow for scope ( and the device) cooling will be provided?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 13, 2018, 04:25:49 pm
content: Quote from: Bud on January 13, 2018, 04:20:10 pmWater is somewhat thermally conductive, so as long as the case walls aren't too thermally insulated heat shouldn't be a problem.

author: Cyberdragon
author_rank: Super Contributor
timestamp: January 13, 2018, 08:51:56 pm
content: Why are you restricted to benchtop? Why not look into handhelds?The problem is you'd need to find one that's waterproof, has four channels (or two dual channel ones), and has remote access.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 13, 2018, 09:02:55 pm
content: Quote from: Cyberdragon on January 13, 2018, 08:51:56 pmIt's in an enclosure, the issue appears to just be remote access

author: nctnico
author_rank: Super Contributor
timestamp: January 13, 2018, 09:05:38 pm
content: For this purpose I'd get something which has been designed to be used remotely. Picoscope may have something suitable. A regular benchtop scope doesn't have the software to do remote operation very well.

author: Cyberdragon
author_rank: Super Contributor
timestamp: January 13, 2018, 09:16:52 pm
content: What about the Fluke 190 series handhelds? They say something about hands-free operation.

author: Rick Law
author_rank: Super Contributor
timestamp: January 14, 2018, 09:43:55 pm
content: Quote from: boumboauto on January 13, 2018, 01:22:03 pmYou really have to specify how deep is the water and how you plan to use it to get a sensible answer.2 feet down? 100 feet down? 36,000+ feet down? Each will require very different machines.- For two feet down, you can probably route the signal to above water.- For 100 feet down, now it is beyond just wet. Water pressure is an issue. All seals need special care. The enclosure needs to be design not just to block water but also to withstand pressure.- For use down at the Mariana Trench... at 36,000+ feet down, you better be in good standing with your God. There is a good likelihood you will meet him/her before you get your measuring device working.

author: Jeroen3
author_rank: Super Contributor
timestamp: January 15, 2018, 12:32:51 pm
content: Quote from: boumboauto on January 13, 2018, 01:22:03 pmThe rigol is only 100MHz when you're usingonechannel. It's 25 MHz on 4 channels.See below.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 15, 2018, 12:47:32 pm
content: Rigol DS1054Z has 100MHz capability with all 4 channels active. Same 100MHz as for 1 channel only. The 100MHz bandwidth is coming from the analog front end, and not from the ADC sample rate.The ADC sample rate is 1GSa/s in 1 channel mode, 500MSa/s in 2 channels mode, 250MSa/s in 3 or 4 channels mode.

author: SVFeingold
author_rank: Frequent Contributor
timestamp: January 15, 2018, 02:54:47 pm
content: Can't remember anyone asking "Should I get the $400 scope or the $16k scope?" It sounds like you aren't quite sure of your requirements, but in any case I'd wager that $16k is far more scope than you need for this. How fast are these transients you need to capture?Although it's not your money you'll be spending, have you ever designed an underwater enclosure before? How deep is this?

author: daqq
author_rank: Super Contributor
timestamp: January 15, 2018, 03:03:52 pm
content: The cheapest option would probably be a cheap USB scope + some embedded PC to which you connect via remote desktop.

author: JoHr
author_rank: Regular Contributor
timestamp: January 16, 2018, 02:08:14 pm
content: I´d propose a RTB2000 due to its low fan activities ...https://www.rohde-schwarz.com/nl/product/rtb2000-productstartpage_63493-266306.htmlor an R&S RTH Scope Riderhttps://www.rohde-schwarz.com/nl/product/rth-productstartpage_63493-156160.html( battery driven, fanless, has a remote access via webserver as well )But I´have no idea what that would be in your enclosed environment ...

author: free_electron
author_rank: Super Contributor
timestamp: January 16, 2018, 03:22:53 pm
content: Quote from: boumboauto on January 13, 2018, 01:22:03 pmso .. get an ethernet based scope. simple ethernet switch and off you go.bitscope has an ethernet machine.https://rlx.sk/en/pc-oscilloscopes-usb/2672-cs328ae-ethernet-oscilloscope-10bit100msas-2-analog-8-digitalisolated-ethernet.htmlrigol has one too i think

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 16, 2018, 04:57:10 pm
content: BTW This is the RTB2004 network modehttps://youtu.be/mcgJSKxj0i0?t=266Also, if you need something small, it may be possible to re-case the main PCB - I think you may also need the front panel PCB but you should be able to omit the display

author: billfernandez
author_rank: Regular Contributor
timestamp: January 16, 2018, 06:01:04 pm
content: National Instruments may have something you can use (although if this is a hobbyist project in might be too expensive). They specialize in data acquisition modules that are computer controlled and remotely connected.http://www.ni.com/en-us/innovations/technology.html

author: JoHr
author_rank: Regular Contributor
timestamp: January 17, 2018, 07:57:02 am
content: Which kinds of acquisitions do you want to take?Just a acquisitions of your switching cycles or is it more like a long term measurement?-----------------------------------I´ve not seen a scope until now which can stream such enormous amount of acquiered data...On the other hand you may get a lot gaps between acquisitions.There for a logger might be better...

author: tautech
author_rank: Super Contributor
timestamp: January 17, 2018, 08:09:49 am
content: After 3 days, not a peep from the OP.He might like to check the SDS1*04X-E LXI speeds found in this thread:https://www.eevblog.com/forum/testgear/open-source-lxi-tools-and-liblxi-v1-0-released-for-gnulinux/msg1394796/#msg1394796

author: boumboauto
author_rank: Contributor
timestamp: January 24, 2018, 09:05:41 pm
content: Sorry for all the confusion, the oscilloscope does not need to be waterproof, it will not be directly immerged into the water. It will be in a watertight enclosure.The point is to measure voltages at the 3 phases + neutral point of a motor driven by an inverter in order to see if the inverter is doing his job properly.The voltage to ground to be measured will be between 0V and 2000V depending on how fast the motor is spinning.I was more oriented towards the picoscope + embeded PC option, but I like the RS2000 idea, does it has a fan ? Otherwise the NI cDAQ seems to be a good option as well.The scope will be in a harsh electromagnetic due to the close by frequency converter driving the motor.Thanks to all for your suggestions and sorry for the late reply ;(

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 24, 2018, 09:15:57 pm
content: Rtb has a fan but doesn't run that fast. Total power draw about 60W, but you could reduce by disconnecting the lcd/backlight

author: Old Printer
author_rank: Frequent Contributor
timestamp: January 28, 2018, 07:21:04 pm
content: Another question is how hard will it be to access the enclosure once submerged? Is this a backyard project or a corporate venture? If it is a serious commercial project I would not send down the cheapest scope on the market. A quality USB scope like a PicoScope with ethernet, and depending on the situation possibly a second for redundancy. The demands don't sound like a high end scope is necessary, but reliability sounds paramount.