|Product Performed to Expectations:||8|
|Specifications were sufficient to design with:||10|
|Demo Software was of good quality:||8|
|Product was easy to use:||10|
|Support materials were available:||10|
|The price to performance ratio was good:||10|
|TotalScore:||56 / 60|
I will start this RoadTest by explaining what it is that I'm testing: it's a "reference design" of a wireless multimeter.
That means I'm not just testing a multimeter here, but also looking into the tools they are providing me in terms of different sample circuitries and software.
On the surface, it's a really great little tool, slightly bigger than a pen, maybe comparable to a big sharpie-type marker. The first image compares it to my main multimeter, the 2nd is the "unboxing" image, and the 3rd compares it to an AA battery and an iPhone5. Note that they currently do not have an iPhone app available, so that iPhone is just a prop. I live my life on an Android phone that I used to take the picture, and that I used to run the companion app, so all is ok.
This multimeter connects to a smart phone or tablet via bluetooth. The smart phone provides the display, which opens up a lot of capabilities without adding to the complexity or cost of the multimeter. This multimeter is fairly limited in what it can do: it only tests voltage and amperage, not resistance, capacitance, or inductance, but that's not the point of this exercise - it's for reference, not for sale. Plus for this reference design they've kept the voltage capabilities to just 50V - good idea, since it doesn't have a cover
Note to self: don't lick the exposed circuitry while testing higher voltages.
A Reference Design
A "reference design" is essentially the hardware version of what us software types call "sample code". And that's in addition to the actual sample code they also provide to go with it. Rather than simply throwing some chips at us and telling us what they can do, the brilliant minds at Texas Instruments are actually taking the time to show us HOW. In the past I've dealt with several electronic creations, including some small display modules from brand-name companies, where it was extremely difficult to get started simply because the sample code was incomplete and limited, and there were no hardware reference designs to speak of.
In my opinion, Texas Instruments is really setting themselves apart by spending the time and money to create REAL designs, coupled with REAL software, that can be used by engineers to more quickly and more reliably create their own projects based on the building blocks provided. This is a nice change from companies that rely on their communities to figure it all out, which often leads to days of searching and inefficient, often dangerous, results.
TI, in their documents, state that the main reason for putting this particular piece of hardware together was to demonstrate how to use Bluetooth Low Energy (BLE) to connect the CC2640 microcontroller to an Android device, as well as how to pair using the RF430CL330H NFC transponder. Part of the reason for such connectivity is to allow designers to choose to use Android devices for their human interface, and thus saving money while increasing capabilities. I totally agree that this is a brilliant way to do that.
While for myself I'm not likely to create a digital multimeter, I can see myself using a BLE connection to other devices (like my greenhouse controller or hummingbird feeder heater/monitor) to make the UI easy to build. As I'm mainly a software guy, and specializing in mobile apps right now, this is right up my alley: using an Android app to control my projects is ideal.
This reference design also uses a lot of other smaller pieces that I'm not fully familiar with, but here are a couple of pieces that even this hardware hobbyist/novice finds interesting:
I'm quite fond of the new Lithium battery technology, as I'm sure most techies are - more power available in convenient packages. I've been using 18650 batteries in flashlights for a few years now, and the difference at night is nearly day (hahaha groan, sorry). This RoadTest introduced me to a similar battery, the 10440 standard - it's the AAA version of the 18650 really. Same voltages (3.7 nominal) and charging requirements in an even smaller package.
To easily work with these batteries within our own design, TI, in this reference design, shows us some very nice chips we can use:
By the way, these things are TINY!
Of course when powering low power devices you need power efficient regulators to go with it, and they show 4 different ones in use in this design.
What's also interesting to note is that on their website TI provides even more information for each of the parts, in the form of more focused reference designs, as well as tools that help you find the parts most suitable. Check out the right-hand-side of this page (I added the "note!" arrows)...
Using the Multimeter
I found this multimeter to be quick and easy to set up and connect - the longest wait was the app download itself, which was not long at all, meaning everything responds very quickly with very little lag trying to find and connect to the hardware.
The Android app connects to the multimeter quickly via Bluetooth, but I was not able to pair it via NFC. According to the documentation, that requires an NFC antenna to be connected to the multimeter.
It does mention being able to pair via Bluetooth by using the "settings", but I was not able to find that feature anywhere in the app.
This wasn't really a big deal, as it does connect very quickly when picked from the list. The unfortunate part is that a software example of pairing to the device could be handy for those wanting to create their own projects.
With there being an indirect connection between the app and the hardware, you might think there would be some delays when doing test readings, but I haven't found that to be the case - the tests are quick and the UI updates instantly.
One definite advantage of a wireless link like this that I can see being useful in an industrial design is that there isn't a direct link between the tester and the hardware, and therefore no chance of the person getting injured (due to electrical shock) if something did go wrong.
I did run into a small bug - after first inserting the battery, the volt meter did not work until I switched the physical "mode" switch to Amp and then back to Volts again. Luckily this was only an issue at startup, and there's no need to ever replace the rechargeable battery. However, new users could think that they received a defective device.
This is what I saw when I tested a 9 volt battery after first inserting the battery:
After figuring that out, here are some more random tests I did, which all gave easy to read, stable results.
It also has a cool graphing feature, which I tested using a flashing multi-coloured LED:
The app should probably request that the OS doesn't sleep, as it was a bit annoying that my phone went to sleep while I was trying to take various tests.
For my tests, I didn't find the 50 volt limit an issue; however, the 50 mA limit meant that I couldn't use it to test current draw for my hummingbird feeder heater, or for my sprinkler valve, so I just played around with some LEDs to give it a try.
One bug that I found rather confusing was that choosing the current range of 500 uA or 50mA didn't show me a clear out-of-range indication. Usually multimeters show a 0 or -1 to indicate the value being out of range.. While testing the LEDs, I couldn't quite figure out from the UI which the correct setting to use should be.
The other thing I felt needed to be there was a charge indicator - either in the circuitry or in the app. I could tell that the battery was charging because the battery gauge % did go up slowly over time. This is the kind of reference circuitry (or software) detail that I would want as part of a battery management system in a custom project. I'm not sure if the software may be able to determine battery charge and it's just a lack of UI at this point, or if it's something that needs to be added to the hardware.
Final thoughts and take-aways
Texas Instruments is doing an amazing job at providing high quality circuit designs along with well designed software for their hardware components. This RoadTest opened my eyes to some of the possibilities with regards to the specific hardware, but also opened my eyes to the company - I now know to look at TI as a source of reference material and designs when it comes to getting ideas on how to build my own projects.
The design of the multimeter and the related app is also excellent, showing that TI is investing in some quality engineers, and allowing them the right amount of time to build high quality examples for their components. There are a few glitches that could be cleared up, but overall the results are very useable.
I would have liked a proper enclosure for this product though, because it's something I would like to use more regularly. A clear shrink cover would probably do the job. Maybe one day they'll supply some 3D print designs
And I wish I had more time to really dig into the software - I did spend quite a few hours over several days porting parts of the Android source code over to a little demo iPhone app, but unfortunately I'm not well versed enough with BlueTooth to pull this off in the time I had available over the past couple of weeks. I will most likely return to it at some point in the near future though.
This is the main TI page for this item: TIDA-01012 Wireless IoT, Bluetooth® Low Energy, 4½ Digit, 100kHz True RMS Digital Multimeter Reference Design | TI.com
The TI page for the software, which includes schematics, design files, and Android source code: TIDC-01012 Industry 4.0 NFC and Bluetooth® Low Energy User Interface Reference Design for IoT Metering | TI.com
The original E14 RoadTest page: TI Wireless IoT Bluetooth Digital Multimeter
My blog on E14: Nico teWinkel's Blog
A pre-RoadTest blog post, which includes the obligatory picture of a cat: TI Wireless Bluetooth Digital Multimeter - pre-Roadtest
My blog in the wild: http://techblog.mulberryland.com/
This was a RoadTest: the hardware was provided by Element14 and Texas Instruments.