CurrentRanger review & availability

Sunday morning I woke to an unusual amount of email asking about the CurrentRanger availability. And the limited stock was all gone, so I knew something happened.

I was then pointed to to Andreas Spiess’s latest video:

Thanks to Andreas for posting a thorough review of the CurrentRanger, I especially appreciate how he was able to quickly tune the code to his own needs and customized the CurrentRanger to behave the way he wanted.

He also kindly posted a 3D printable model of the case he shows in the video, some folks already printed it and it looks great! Find it on thingiverse here. The stock case needs some modification to fit the green terminal and access to the USB case, as well as allow mounting the buzzer. If you have a 3D printer you can print this case and keep the black stock case for another project, thanks Andreas!

Availability

I am working to get more units in stock this week. There are a lot of moving parts to making this product. First a large BOM and a complex assembly and testing procedure. I want to ensure to the best of my ability that each unit is able to deliver what it claims.

Some components like the banana jack terminals and OLEDs come from the place we hate to love, China. I’m currently waiting for the small banana jack terminals and OLEDs. However I have a surplus of GOLD terminals, and could replace the small terminals with those if some folks are interested – let me know!

Pricing

I can understand concerns about the cost especially for hobbyists or students. Let me reiterate what I’ve already mentioned in the forum and to others. Here’s the TL;DR of that:

I always tend to design something that I would first and foremost use. While not a high end product, this is not a toy either. I spent over a year – among other things of course 🙂 – developing this product and I put a lot of thought into pricing it before release. I’m not interested in selling high volumes at razor thin returns on my investment and my effort. I prefer fewer sales for people that can appreciate it and not abuse it. I think it was priced fairly, given the high cost of the BOM and the complexity and time it takes to make and test, it really is probably the most complex thing I ever made both in hardware and software. Also, it is not much more expensive than the uCurrent, I am sure anyone reasonable who understands the differences and the set of extra features (perhaps watched the video above for some contrasts), can appreciate all that for just $30 more. The uCurrent is always a great option for those needing accurate current measurements at a lower price.

CurrentRanger: auto-ranging current meter

I’ve always wanted a fast auto-ranging low-burden voltage current meter. You may find expensive high end bench meters which can auto-range they may be slow or lack the bandwidth to capture fast dynamic loads that go through several orders of magnitude of current consumption. Most multimeters also have a large burden voltage, which means their internal current shunts can cause your DUT to see a very significant voltage drop.

I own a µCurrent GOLD from EEVBlog which is great in that it has the precision and bandwidth to capture fast current transients, but it’s a simple manual device that cannot auto-range and unfortunately it’s really noisy in the nA range where it picks up mains noise and it’s unusable without an extra cap on the input (I thought mine was broken but this problem is also reported in the EEVBlog forum here and here). It’s useful when you know your DUT is going to stay in 1 range or if you can predict when your DUT might wake up from deep sleep and manually range just before that happens but it’s a guessing game. Hence the mechanical switches get a lot of abuse and wear, add output noise during switching, and introduce some contact resistance with noticeable effect in the mA range.

Looking around, I couldn’t find much else in terms of affordable fast auto-ranging and highly precise ammeters. So over year ago I started to design my own version of a current meter that has the precision and bandwidth, can auto-range, and has some extra nice-to-have features like:

  • Low pass filter for smooth oscilloscope tracing
  • Unidirectional measurement mode by default for maximum measurement range
  • Standalone OLED display
  • Bluetooth logging would be nice
  • Buzzer for tactile feedback (and why not also play some Beethoven on power-on)
  • Auto-power-off to spare the battery, oh how I craved this simple feature
  • LiPo powered, rechargeable, easily re-programmable – wouldn’t all that be great?
  • Great value vs. features without breaking the bank

It was a bit ambitious and immediately became obvious that this needs to be digitally controlled by a microcontroller to do all that. Five prototype revisions and a year later I think the result is finally ready for release. So I’m pleased to introduce the CurrentRanger, click here for full specifications and user guide.

As a side story – out of the birth pains of the CurrentRanger, resulted the Moteino M0 which uses the same SAMD21 ARM processor that controls the CurrentRanger.

The CurrentRanger is now available in the shop. Please let me know if you did something interesting with this meter. It’s certainly a complex device with a large BOM and lots of parameters to test. With your help I think it can be made even better in so many ways. As resources/code/new features become available they will be added in the CurrentRanger Guide.

Enjoy!