Oscilloscope > 4 channels...... Saleae or something else? - Page 1
Forum section: electronics / testgear

author: Jester
author_rank: Frequent Contributor
timestamp: November 30, 2018, 11:07:57 pm
content: I have a decent 1G, 4 channel oscilloscope that meets my oscilloscope needs 99% of the time, however once in a while I sure could use an extra channel or two. I have been searching lower cost PC based multichannel scopes and logic analyzers to see if I can find something suitable. For this 1% case I don't need super bandwidth (I will use my existing scope for that), 10MS/s per channel should be adequate. 8 channels would be great.PicoScope has an 8 channel model 4824, however at $2300 fails the dirt cheap criteria.Saleae LogicPro8 looks like it will meet my desired specifications at about $500I also looked at DSLogic, however it looks like these (although less expensive) do not support analog mode.Perhaps there are better / less expensive options?

author: nctnico
author_rank: Super Contributor
timestamp: November 30, 2018, 11:14:26 pm
content: Less expensive... probably not but Yokogawa has several models with more than 4 channels (up to 16). Getting a used one should keep the price down.

author: DaJMasta
author_rank: Super Contributor
timestamp: November 30, 2018, 11:14:51 pm
content: You could look at much older scopes, I believe Yokogawa made some 8+ channel scopes which would give you a normal sample rate. Maybe something like a USB DAQ? 10MS/s may be tough for some of the multichannel options, but they likely have some sync functionality so they can be used together, so if you can find one with the sample rate, the software to use them together would probably be taken care of.

author: alm
author_rank: Super Contributor
timestamp: December 01, 2018, 08:38:03 am
content: Quote from: Mechatrommer on December 01, 2018, 05:43:33 amThis topic is about analog channels. How many analog channels does that clone have?

author: Fungus
author_rank: Super Contributor
timestamp: December 01, 2018, 09:14:21 am
content: Quote from: Jester on November 30, 2018, 11:07:57 pmIf your 'scope has a trigger out then you can connect it to another 'scope and chain them. It's not quite as convenient as having all traces on a single screen but it works.Otherwise you probably need to go to a USB. Also inconvenient if you're not used to working that way and probably more expensive than a Rigol DS1054Z if you want more than 4 channels.

author: Jester
author_rank: Frequent Contributor
timestamp: December 01, 2018, 02:57:00 pm
content: Quote from: Mechatrommer on December 01, 2018, 05:43:33 amJust for giggles I ordered one even though it won't meet the 10MS/s criteria (when using more than 2 channels, 24MS/s), hard to go wrong for $5This one @ $36 and 100MS/s, might just do the trickhttps://www.ebay.com/itm/New-USB-Logic-100MHz-16Ch-saleae16-Logic16-Logic-Analyzer-for-ARM-FPGA/123448628672?hash=item1cbe1c95c0:g:o4sAAOSwQFNb0Q3s:rk:1:pf:0They claim it works with the latest version of Saleae software.Not sure on the full scale analog range though, seems like some of the older ones were only good for 0-5V, while the newer ones are good for +/-10V, let's hope its the +/-10V variety. Not sure on the input impedance either. If it works, it might be worth making a buffered input circuit to increase the input impedance and provide some protection.I also found a really cheap (<$79) Hantek 8 channel automotive scope with BNC connectors and 1Minput impedance. Claims 2.4MS/s, so perhaps 30kHz bandwidth going down hill with a tail wind.https://www.ebay.com/itm/Hantek-1008B-8-Channel-Automotive-Diagnostic-Oscilloscope-Programmable-Generator/182395868071?epid=1839529087&hash=item2a77a413a7:g:1YkAAOSwz3RbummN:rk:3:pf:0Unfortunately the few comments and videos that I found make it seem more less unusable as the firmware appears to be half baked at best.

author: colorado.rob
author_rank: Frequent Contributor
timestamp: December 01, 2018, 03:00:23 pm
content: What are you measuring on your scope if the Salea is an option for you? If it will work for your needs, then it is a great option. The storage and decoding capabilities exceed any scope I have used.

author: nctnico
author_rank: Super Contributor
timestamp: December 01, 2018, 03:10:04 pm
content: Quote from: Fungus on December 01, 2018, 09:14:21 amIt won't work. On a DSO the trigger output will be aligned with an internal clock and not be exactly synchronised with the actual trigger event. This causes jitter to show int the signals. Getting rid of the jitter would require on-the-fly picosecond delay adjustments. Also the trigger output is likely not aligned with the actual trigger event.This screendumps shows the trigger out looped back into the second channel (green trace). You see there is jitter and the trigger out isn't aligned with the actual trigger event.If you want to daisy chain DSOs they will need picosecond level time synchronisation and communicate the trigger point so each DSO can display the signals with respect to the same time offset.

author: Jester
author_rank: Frequent Contributor
timestamp: December 01, 2018, 03:11:05 pm
content: Quote from: colorado.rob on December 01, 2018, 03:00:23 pmAs mentioned in my original post my Tek DPO scope works great 99% of the time, however every once in a while, a few extra channels would be handy. Yesterday I was troubleshooting a power system protective relay, so I was measuring 3 phase current plus several digital signals related to the trip circuit. So nothing fast, just more than 4 channels.

author: Jester
author_rank: Frequent Contributor
timestamp: December 01, 2018, 03:19:23 pm
content: Quote from: nctnico on December 01, 2018, 03:10:04 pmThe dual scope idea would have worked in my last case, because a 1/2us would be irrelevant, not having to cram another scope in my work area is a plus, the Saleae is just right size wise.

author: Fungus
author_rank: Super Contributor
timestamp: December 01, 2018, 03:20:39 pm
content: Quote from: nctnico on December 01, 2018, 03:10:04 pmWell ...a) The OP said that 10MSa/sec should be plenty for his needs so jitter would be minimal.b) A simple BNC splitter could feed the triggering signal into both devices. It's slightly less flexible but he said he only needs it occasionally.

author: Roeland_R
author_rank: Regular Contributor
timestamp: December 01, 2018, 03:21:04 pm
content: Back in the eighties at school we created a chopper to turn a single channel scope in a dual channel. You need z modulation on the scope for a good picture. Usable for low frequency.

author: Fungus
author_rank: Super Contributor
timestamp: December 01, 2018, 03:22:08 pm
content: Quote from: Jester on December 01, 2018, 03:19:23 pmIf you already have a PC in the area then it should work.

author: nctnico
author_rank: Super Contributor
timestamp: December 01, 2018, 03:31:58 pm
content: Quote from: Fungus on December 01, 2018, 03:20:39 pma) if the samplerate is lower, the jitter is likely to be higher as well so this problem will remain. b) Feeding the trigger into both device won't work at all because you'd be feeding an output back into an input.

author: Gyro
author_rank: Super Contributor
timestamp: December 01, 2018, 04:09:11 pm
content: Quote from: Jester on December 01, 2018, 02:57:00 pmYes, they do work. They're an FPGA included step up from the $5 ones. They emulate theoriginalSaleae Logic 16. Digital only, no analog channels. Maximum frequency increases as you drop the number of channels in use. Note however that they are fixed 3.3V logic levels, with 5V tolerance, changing the input threshold in the Saleae software does not change the device. They claim higher maximum voltage protection but I wouldn't risk +/- 10V. I think input resistance is 100k - impedance however has a lot more to do with lead capacitance etc at high frequencies.To be ethical you should use it with open-source Sigrok Pulseview s/w rather than Saleae. Here is the Sigrok page for the variant currently on sale (I think)...https://sigrok.org/wiki/Noname_XL-LOGIC16-100M

author: Jester
author_rank: Frequent Contributor
timestamp: December 01, 2018, 05:17:37 pm
content: Quote from: Gyro on December 01, 2018, 04:09:11 pmDigital only, that's unfortunate. I guess the genuine Saleae Logic8 must rely on an actual A/D instead of the clones digital inputs, because the Saleae specifies Digital sample rate of 100MS/s and Analog sample rate of 10MS/s for the Logic8

author: Fungus
author_rank: Super Contributor
timestamp: December 01, 2018, 05:40:14 pm
content: Quote from: Jester on December 01, 2018, 05:17:37 pmYep, that's why the real ones cost more.(plus they have to pay for the software development, etc., while the Chinese only have to make theirs "compatible")

author: Gyro
author_rank: Super Contributor
timestamp: December 01, 2018, 07:01:07 pm
content: What you have to remember with Saleae, is that they had anoriginalline-up, the Logic 8 and the Logic 16 (these are the ones that are cloned on ebay). They were digital-only, in over-engineered milled cases (Dave has a review of them somewhere), now discontinued but still supported. Then there are themore recentproducts, like the Logic8 which have analog capability. Their product history naming convention is confusing [Edit - as you're finding].The original Logic 8 was no more than a clone of the Cypress EZ-USB FX2 eval board itself, in fancy case. In the Logic 16 is where they learned to put an FPGA in for higher performance / flexibility. It's only the more recent products that they got more inventive with their hardware. The user-friendly software was their original USP - hence it's a bit naughty to use it with clones (even though they are no longer competing with their current product range).

author: Jester
author_rank: Frequent Contributor
timestamp: December 01, 2018, 07:21:21 pm
content: Quote from: Gyro on December 01, 2018, 07:01:07 pmI'm not sure how accurate the following is as I read it during one of my google searches..... The initial source of all of this (including a major software effort) was an open source project, however at some point a branch occurred where all references to the open source aspect of the software were removed from the software and a product and a company were formed based on the initial open source project that branch then became proprietary. I can't recall which of the products or companies they were referring to as there are a few and a lot of clones. One thing for sure not an easy market to be competing in.I will be looking for a genuine PRO 8 or 16 to get the analog capability.

author: alm
author_rank: Super Contributor
timestamp: December 01, 2018, 07:43:48 pm
content: Are you confused with the DSLogic? That was based on Sigrok / Pulseview, and although they released the source code to the software, they failed to integrate this in the Sigrok project and released it in a format that was very hard to integrate.I believe only open source logic analyzer projects of note are the Sigrok project (which I'm pretty sure appeared after the original Saleae Logic) and the SUMP logic analyzer, which was based on an FPGA rather than an EZ-USB SoC.

author: David Hess
author_rank: Super Contributor
timestamp: December 02, 2018, 01:42:50 am
content: Quote from: Jester on December 01, 2018, 03:19:23 pmI faced the same problem at one point but my solution was to get oscilloscopes which stacked. Shown below is my 6 channel Tektronix 22303230.

author: Jester
author_rank: Frequent Contributor
timestamp: December 02, 2018, 02:17:16 am
content: I think the Saleae, wins or looses (depending on your perspective) the size battle. It's been a while since I twiddled the knobs on a Tek 2230

author: cdev
author_rank: Super Contributor
timestamp: December 02, 2018, 02:49:05 am
content: One of the USBee models was the first FX2 LA to incorporate a MSO. Its not well known but it was of course later cloned and also I think there is also a commercial very similar USB LA/MSO now - all of these devices use the very versatile FX2 and FX2LP and build upon it with various other HW.