Inexpensive Differential Oscilloscope  - Page 1
Forum section: electronics / testgear

author: timwolf
author_rank: Contributor
timestamp: February 04, 2022, 05:10:30 pm
content: Hello everyone,I'm looking to upgrade my starter oscilloscope, and I'm looking for an inexpensive oscilloscope with differential probes since I've been recently doing a lot of measurements on split grounds.Much appreciated-Tim

author: Fungus
author_rank: Super Contributor
timestamp: February 04, 2022, 05:13:15 pm
content: What's your "starter oscilloscope" and what's your budget?

author: timwolf
author_rank: Contributor
timestamp: February 04, 2022, 05:18:11 pm
content: My starter scope is a RIGOL ds1054z, I'm looking at something around $500-1,500K, but i'll go up to 3k if it's really good and worth the extra dough.Best RegardsTim

author: bdunham7
author_rank: Super Contributor
timestamp: February 04, 2022, 05:32:42 pm
content: We'd need to know what bandwidth and voltage you require for your differential measurements. If the voltage and BW are reasonably low--like PSU and audio stuff, then the two-probe + MATH method will actually work pretty well with your scope--no purchase required. If you need more BW or more voltage, getting a good quality, high CMRR solution starts to go up in cost very quickly.There are differential probes available in the $100-500 range (per probe, per channel) from MicSig and Sapphire (sold under many brand names) that work OK, but with limitations. Then there are isolated channel oscilloscopes like the handheld Fluke Scopemeters and similar products from other brands, as well as the Tektronix TPS2000 series, but those are pretty pricey unless you get them secondhand. They also tend to be pretty limited in functions.There are also a few stand-alone optical interfaces like the Siglent IFE (cheap but limited) and the large-box Sony/Tek A6909/A6907.Things just keep going up from there all the way to the Tek IsoVue that is literally a million times as good as the MicSig stuff but for $30K per probe.

author: timwolf
author_rank: Contributor
timestamp: February 04, 2022, 05:49:48 pm
content: I've been pretty happy with (100Mhz, 4 channels, 1Gsa/use, 1Mpts fft) any improvement on that would be great I measure around 0-60V, and I mostly work on DC/DC converters in the 500khz - 1Mhz range, and inrush current limiters.

author: tautech
author_rank: Super Contributor
timestamp: February 04, 2022, 06:32:06 pm
content: An updated version of the SHS1000 series is not far away which are handheld scope meters with 2 isolated channels.The USB powered ISFE module can also be useful but its BW is limited and it’s input attenuation is set at 200x.

author: Fungus
author_rank: Super Contributor
timestamp: February 04, 2022, 06:46:14 pm
content: Quote from: timwolf on February 04, 2022, 05:49:48 pmYou don't need a new 'scope for that, just some differential probes.The Micsig probes already mentioned are good and come in three different levels depending on your maximum voltage.Prices are very reasonable.http://www.micsig.com/html/41.htmlIf you really, really want a new 'scope and have a couple of thousand to spend then the Siglent SDS2000 is probably the one to go for. I'd start by getting the probes though and see what your Rigol can do with them. The probes will work with other 'scopes in the future.

author: bdunham7
author_rank: Super Contributor
timestamp: February 04, 2022, 07:00:06 pm
content: Quote from: timwolf on February 04, 2022, 05:49:48 pmI would start by experimenting with two probes set to 10X and using the MATH (subtract CH2 from CH1, regard CH2 as your 'ground') function. Once you see how well that does or doesn't work, you can consider other options. There is no reasonably priced inherently isolated scope that I know of that is going to be both isolated and otherwise as good or better than what you have already. It makes much more sense to add the isolation separately.Every solution has its drawbacks. The Siglent IFE may barely meet your needs, but its sensitivity works out to 1V/div at best, and BW 1MHz at best. The MicSig DP10007 might be better, but that still has 15mV input noise and the CMRR isn't great.