µCurrent Probe - CMicrotek : Ultra-low current measurement tools - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: February 26, 2014, 11:34:33 am
content: No, it's not mine.It seems they have trademarked the name "µCurrent Probe"http://www.indiegogo.com/projects/cmicrotek-ultra-low-current-measurement-toolsNot sure how they could have researched this field and developed the product without knowing about my µCurrent? To use the same name is pretty silly and confusing.

author: hli
author_rank: Frequent Contributor
timestamp: February 26, 2014, 01:13:58 pm
content: Their spec sheet for the uCP100 claims a bandwidth of 3MHz, with a gain of 200 (5µV voltage drop to 1mV output for 1nA current).I would guess they copied the µCurrent design with some enhancements (higher output voltage) and forgot to read about the limitations...

author: SpectrHz
author_rank: Contributor
timestamp: February 26, 2014, 02:03:59 pm
content: What in the world is with those perks? It looks like they are just clearing out their attic and using it as perks... Nat geo dvds?? Only 3 or so of the perks apply to the campaign, is it standard practice to do this for IGG? I've never done any crowdfunding except the uRuler so, I'm a bit confused.

author: Sigmoid
author_rank: Frequent Contributor
timestamp: February 26, 2014, 03:30:28 pm
content: Quote from: SpectrHz on February 26, 2014, 02:03:59 pmNo it's not you. These perks are ridiculous, the entire campaign is incredibly unprofessional. I wouldn't pledge a penny to these people.

author: Neganur
author_rank: Unknown
timestamp: February 26, 2014, 05:56:39 pm
content: that video confused me, what is he trying to do again - save the world or promote a product?

author: Sigmoid
author_rank: Frequent Contributor
timestamp: February 26, 2014, 06:18:45 pm
content: Quote from: Neganur on February 26, 2014, 05:56:39 pmThe whole thing sounds like the naive environmental activism crap we did with friends in elementary school. The whole thing is nonsequitur. The guy may have 30 years experience in bringing electronic devices to market, but he has the marketing savvy of a 6 year old.

author: EEVblog
author_rank: Unknown
timestamp: February 26, 2014, 10:15:00 pm
content: Quote from: Neganur on February 26, 2014, 05:56:39 pmI was pretty bamboozled too.Looks like they took too many marketing pills at the Startup America course and have gotten all confused.

author: pickle9000
author_rank: Super Contributor
timestamp: February 26, 2014, 10:37:28 pm
content: Maybe he is trying to target an established customer base with a similar product.

author: EEVblog
author_rank: Unknown
timestamp: February 26, 2014, 10:40:26 pm
content: Quote from: pickle9000 on February 26, 2014, 10:37:28 pmWell if he's knowingly doing that and deliberately using the same name, then that's a real dick move.

author: dr.diesel
author_rank: Super Contributor
timestamp: February 26, 2014, 11:00:31 pm
content: Ha talks about the medical industry needing a low current measurement system to further their designs, specifically artificial hearts. Like the medical industry is browsing Kickstarter in the search of T&M gear, ha ha ha,.

author: pickle9000
author_rank: Super Contributor
timestamp: February 26, 2014, 11:09:26 pm
content: Here is his bio. Looks like a company just over a year old.http://www.linkedin.com/in/mikeleaseI can't think of any circumstance where he did not know of your product beforehand. At the very least he should say that he is not affiliated/connected to/with the Dave Jones ucurrent.I like a good head to head product battle but not something that appears to be sneaky.

author: EEVblog
author_rank: Unknown
timestamp: February 27, 2014, 01:32:11 am
content: Quote from: pickle9000 on February 26, 2014, 11:09:26 pmI just heard from the designer Mike, and he claims he had never heard of me (and presumably the µCurrent) before someone posted a comment of "nice rip-off of Dave Jones" on his campaign.Well, ok, I'll take his word for it.

author: Legit-Design
author_rank: Frequent Contributor
timestamp: February 27, 2014, 01:48:23 am
content: Maybe he doesn't know EEVblog and Dave Jones are connected? It could happen.Indiegogo + flexible funding = dodgy all the way

author: EEVblog
author_rank: Unknown
timestamp: February 27, 2014, 01:57:46 am
content: Quote from: Legit-Design on February 27, 2014, 01:48:23 amThe comments are hidden too.I'm not sure why anyone would contribute to these types of flexible campaigns, as you run the risk (even greater than normal) of the developers running out of money before they can deliver anything.This is the µCurrent Probe PCBI see 4.99ohm and 4.99K shunt resistors. But the chip numbers look to be rubbed off or photoshopped out.

author: Stonent
author_rank: Super Contributor
timestamp: February 27, 2014, 02:14:27 am
content: Quote from: dr.diesel on February 26, 2014, 11:00:31 pmThey didn't like Agilent's new name either.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: February 27, 2014, 03:02:41 am
content: From the photo:On the analogue(US product) front end.what are the devices with references LC1-4 ? are they single device LC filters perhaps? Anyone know.Does it do two lots of current? Why 4 inputs. maybe different ranges?Not important, just wondering.

author: BravoV
author_rank: Super Contributor
timestamp: February 27, 2014, 03:08:52 am
content: Quote from: Sigmoid on February 26, 2014, 06:18:45 pmActually not this guy to blame for the campaign, but the "other"guyguru I highlighted below ...Source ->http://www.cmicrotek.com/about.htmQuote

author: EEVblog
author_rank: Unknown
timestamp: February 27, 2014, 04:48:13 am
content: From the screen shot:It looks like two separate channels are being used with the two shunts, but in series (perhaps externally wired like that?) on the same current signal.You can see that trace two is measuring the same signal as trace above it, but is allowed to go off full scale.

author: pickle9000
author_rank: Super Contributor
timestamp: February 27, 2014, 05:38:12 am
content: Regardless of the product, it could be a toaster for all I know. The real issue is that if you google ucurrent and are checking out this guy what will you find? Assuming they are not out to deceive (as they say), they should inform anyone looking to invest. That should be done on the .com and the campaign page. I think that would be the very least they could do.

author: hans
author_rank: Super Contributor
timestamp: February 27, 2014, 10:32:57 am
content: Really confusing campaign. My understanding of low power electronics was that it enables battery powered equipment, not that they save the planet (in the end batteries are a necessary evil). If we want to save the earth from CO2 gasses, then we should probably all stop driving a non-electric cars and stop using coal or gas in power plants.Moreover, I don't think much people will do a low-power optimization cycle for anything non-battery powered, unless there is a heat issue. However, heat issues are often resolved with better cooling.The "power analyzer" looks like a very similar to a project I am working on:https://www.eevblog.com/forum/chat/what-are-u-working-on-right-now-%28electronics-related-and-with-picture-please%29/msg331101/#msg331101Shunt is 10 ohms (0.1%). I use the AD8253 INA, which is programmable gain 1-1000x (per order of magnitude).At 1000x gain I get 50nA/LSB. At 100x gain I get 0.5uA/LSB. The AD8253 has 4MHz -3dB bandwidth of 550kHz at G=100. The noise (because I forgot an anti-alias filter) is about 10LSBpp. So 16-bit / 10LSB = 12.7bits roughly usable bits.INA gain error is typically 0.04%. As the shunt is 0.1%, and I have a resistor divider (0.1%) to connect the front-end to the A/D (which is a bit of a pity to throw away so much gain), I get roughly 0.24% DC accuracy.Unfortunately the MCP3911 has a PGA gain accuracy of 4%, and it's auto-zero feature (which can't be turned off) screws the offset cal up every reset. So it has to go in Rev2.However, it does work:https://dl.dropboxusercontent.com/u/207647/PA/330k%20ohm.pngConnecting a 330k ohm resistor (3.3V rail) at 1000x gain over 10R shunt. Nice 50Hz pickup / body resistance. No filtering done. I still think this image is quite noisy.100x gain is probably the most usable range.https://dl.dropboxusercontent.com/u/207647/PA/Noisefloor gain 1000x.pngNoise "measurement" at 1000x gain. 0dB = FS(1300uA).Not sure whether I should open source this project.Anyway, I really wonder what kind of performance this probe/analyzer achieves. It says it has a dynamic range of 1:40000, which sounds to me 15+ bits of resolution, but at the same time the DC accuracy is 2.5% (order of magnitude worse than my power analyzer, or several orders of uCurrent Gold).So 1:40000 is way overkill for an 8-bit or 12-bit scope resolution measurement, but at the same time measurements can be off by 2.5% for a multimeter.Am I missing something?The picture shown could be from a single low-ohm shunt, but with different gain front-ends. You can clearly see the noise at the microAmp graph, not so much on the mA chart. So as one clips you can view the other one for a large scale picture, and use the other for low-current measurements.

author: EEVblog
author_rank: Unknown
timestamp: February 27, 2014, 10:48:34 am
content: Quote from: hans on February 27, 2014, 10:32:57 amThat's how I do I think for such a logger. Overload recovery on the high gain amp would play a role, but if you sample both at once you can get a good overview of large dynamic range stuff.You are still limited by the trade-off on the choice of sense resistor and usable gain though. I think the Mooshimeter tries to use a 24bit ADC, but ultimately only has 2uA resolution.

author: hans
author_rank: Super Contributor
timestamp: February 27, 2014, 11:41:50 am
content: Or possibly the second graph is "digital gain" (as in Camera digital gain vs optical gain) and only amplifies the bits, as the noise shown is clearly quantization noise.Otherwise looking at a signal with 1:40000 dynamic range is kinda pointless on a monitor with 1080 height pixels.Then the clipping an INA is not an usual use-case.In a previous life I have built a logger like I previously described, with 2 INA's at different gains, and also multiple post-gains (all fixed). The software would decide which one to use. Problem: the A/D's in that system alone was 35 euro's, because all A/D's were simultaneously sampling. Since then (when I am building my own) I decided it's best to assume the guy who uses the logger, better knows how it works and how best to use it, and rely on 1 channel with range switching.And then there always is the trade-off between current shunt. As shown, x1000 gain on a 10R shunt & viewing micro amps is right down in the noise. x100 gain is much more "usable".Didn't the mooshimeter also try to make a huge dynamic range, by using few ranges with high resolution? Like 10A / 24-bit? Even if the ENOB is 20, the resolution is 9,5uA/LSB.Possibly another thing to mention is sampling rates; the uPower samples at 250kHz (it says?), my 10uA test was at 12ksps, the mooshimeter probably isn't accurate to 20ENOB beyond a couple of 10's Hz.