Keysight MSOX3000T digital channel memory - Page 1
Forum section: electronics / testgear

author: RossS
author_rank: Contributor
timestamp: March 26, 2017, 03:59:32 pm
content: I'm considering buying a MSOX3014T, but I can't work out some of the details about the logic analyzer after reading the datasheet and searching the forum.The datasheet states:Maximum digital channels sample rate: 1.25GSa/sMaximum digital channels record length: 2 Mpts (with digital channels only)Is that 2 Mpts per channel or shared across all 16? Is there compression here (e.g. is a "point" one transition at a certain time, or does it just fill up the acquisition memory at the sample rate as it would on the analog channels?) How does this change if I turn on one or two analog channels?I'm coming from a PicoScope + Saleae LA, where I have no problem capturing 10+ seconds of analog + digital at 10MS/s for startup sequences and the like, then sifting through it. It would be great to have analog + digital time correlated on one instrument, though maybe not if it means mucking around with segmented memory or capturing events in pieces.Thanks!

author: nctnico
author_rank: Super Contributor
timestamp: March 26, 2017, 04:31:39 pm
content: On Keysight MSOs the memory is shared between the analog and digital channels so when you turn on both analog and digital channels you end up with 500kpts in run mode and 1Mpts in single shot mode. If you are looking for long captures then Keysight is not the manufacturer to look at (unless you want to spend around 6 figures in Dollars).

author: Neganur
author_rank: Unknown
timestamp: March 26, 2017, 06:44:59 pm
content: Quote from: nctnico on March 26, 2017, 04:31:39 pmsix? I think you exaggerate, they don't cost 100k:http://www.keysight.com/en/pcx-x205199/infiniium-9000-series-oscilloscopes?nid=-32534.0.00&cc=US&lc=eng600 MHz, 20 MPts (1 GPts max), US$ 16,529 list price. That is not much more than e.g. the DSOX-4054A or DSOX-3054T.But it is completely beside the point. If you want a scope that you can dump 10s worth of 16 Channels data at 1.25 GSa/s into then I think this is not the scope you are looking for (Salae can't do that either with those settings).Maximum digital channel record length is 2M alone, 1M with analog channels enabled, and you have to set up a single capture trigger to get there else you have only half of that. So using the scope to "stream data" won't be so great unless you can take advantage of segmented memory. But are you really looking at 16CHs of data...?

author: RossS
author_rank: Contributor
timestamp: March 26, 2017, 07:00:48 pm
content: I definitely don't need 16 channels at 1.25GSa/s. Typically I only need ~5 channels at 10MSa/s. But with 1M shared across five channels, that's just a 20ms capture...Of course I'm assuming there's no compression. I'd love confirmation either way. If you turn on more digital channels but don't actually use them, does the amount of data you can record on the channels you are using decrease?

author: nctnico
author_rank: Super Contributor
timestamp: March 26, 2017, 07:09:31 pm
content: There are alternatives out there with typically 10Mpts so you can make a 200ms capture at 10Ms/s:TBS2000 series (R&S)Wavesurfer 3000 series (Lecroy)MSO2000 series (GW Instek)Each of these have their pros & cons. On an MSO you don't have compression because you can't do that on the analog channels.

author: Someone
author_rank: Super Contributor
timestamp: March 26, 2017, 08:57:52 pm
content: Quote from: RossS on March 26, 2017, 07:00:48 pmThere is someone here who is happy to mislead you, but its not divided per channel on the Agilent/Keysight scopes. When turning on the digital channels (all 8/16 of them) the memory is halved/shared between the analog and digital channels so you can see the memory depth halve when turning on the digital channels (or the high-res mode or min-max).Quote from: Neganur on March 26, 2017, 06:44:59 pmIndeed a very big exaggeration and not showing the full picture. Really the OP is asking about 100MPts of memory depth which at the cheapest from the major brands:R&S RTE1024, 100MPts?, $14,600Tektronix MSO5034B, 125MPts, $28,100Keysight MSOS054A, 100MPts, $27,700Lecroy HDO6000-MS, 100MPts, $POA > $20,000and then the off brands:Rigol MSO4014, 140MPts, $3,500Siglent SDS2104X, 140MPts, $2,100

author: Someone
author_rank: Super Contributor
timestamp: March 26, 2017, 09:09:30 pm
content: Quote from: RossS on March 26, 2017, 03:59:32 pmIf a USB scope works for you they're often the best choice for manually picking through very long captures or streaming infinitely, perhaps consider another USB scope with integrated digital channels?

author: nctnico
author_rank: Super Contributor
timestamp: March 26, 2017, 09:42:57 pm
content: Quote from: Neganur on March 26, 2017, 06:44:59 pmThat is cheaper than I thought but adding some options (like digital channels and deeper memory) will increase the price quite a bit (maybe even double the base price).

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 26, 2017, 10:03:10 pm
content: Quote from: RossS on March 26, 2017, 07:00:48 pmThat's assuming the nature of the data is such that you can't use segmented memory to extend the effective capture time.

author: Neganur
author_rank: Unknown
timestamp: March 26, 2017, 10:25:35 pm
content: Quote from: nctnico on March 26, 2017, 09:42:57 pmnot too bad actually, considering the 4000X post purchase mso upgrade is 2.8k USD (1.3k for the 3000X)oh and you do get a free 3000X scope as bonus when you buy an Infiniium...hehEdit, that last attachment is too small to click, sorry

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 26, 2017, 11:31:01 pm
content: Are there any MSOs that allow any tradeoff between number digital channels used and memory depth ?Even 8 vs. 16 would be a good start.

author: MarkL
author_rank: Unknown
timestamp: March 27, 2017, 12:30:52 am
content: Quote from: nctnico on March 26, 2017, 04:31:39 pmIt's actually worse than that. For an X3000 series if you have only digital channels on, then the max is indeed 2Mpts. But if you turn on even one analog channel, the digital points is reduced to 250k. And it doesn't matter if you have 1 or 16 digital channels on. And if any digital channels are on, the analog points are reduced to either 2Mpts or 1Mpts, depending if you have one or two analog channels on in a pair.And this is single shot mode. All the above numbers are halved for run mode because of the double buffering.I have an MSOX3104A and a couple of Saleaes. The Saleae is much more cost effective for long captures. It's usually not a problem to pick a signal or use the MSO's external trigger to sync between them.

author: Someone
author_rank: Super Contributor
timestamp: March 27, 2017, 12:56:49 am
content: Quote from: mikeselectricstuff on March 26, 2017, 11:31:01 pmCompared to an "analog" channel its not a lot of data, but its mostly the relatively "fixed" architecture of the memory systems which prevents a mix and match approach where you could have a specific depth with 3 analog channels and 8 bits of MSO and:adding one more channel (analog or digital) would cause a reduction in the memory depthremoving 2 of the analog channels would increase the memory depthWhat could be interesting if you uncouple the channels is different sample rates on different channels (digital included) but that would get complicated quickly.