Product review: Vernier's Go Direct motion detector (and PASCO's similar product)

Way back in 2010, when I didn't even own a smartphone, I began to explore the use of phone/tablet apps for classroom use.  I wrote, 

I have little doubt that, five years down the line, Pasco and/or Vernier will have updated their data collection line such that the probes work wirelessly with the iPad or equivalent, and the LabPro or LabQuest will be unnecessary.  

They say, either predict the event OR predict the date - never both.  Then you'll always be right.  Within five years, Pasco had indeed made it possible (though not at all easy or cheap) to use their sparkvue app to view the output of their probes.  A couple of years ago the PASCO Smartcart revolutionized motion and force detection in the high school lab.  (I bought a bunch of these.  They're great.)

And finally, as of this summer, I'm seeing all the probes I regularly use available from Vernier and Pasco in a bluetooth version.  I've bought a bunch from Vernier; I've tried out both the PASCO and Vernier versions.  Today I'll focus on just one...

The Vernier Go Direct Sonic Motion Detector

My wife and sidekick, Burrito Girl, can't stand wires.  They look messy, they get tangled... she was amazingly thrilled eight years ago when I bought her a bluetooth keyboard for her computer.  She would love this motion detector.  If she cared about physics equipment, that is.  

It's extraordinarily compact, just a Borg Cube 2.5" on a side.  No wires.  One side - the business end - includes the power button and the sonic generator.  Two of the other faces have a threaded hole for a mounting screw.  And one face includes the microUSB for charging*

* or for connecting to a LabQuest, if you want to.  You don't have to.

There's no demand for a dedicated interface - no LabQuest, LabPro, ULI*, etc.  It sends its data via bluetooth to the smartphone or tablet.  And the app couldn't be simpler.  The "Graphical Analysis 4" app is free to download.  You open the app to connect the motion detector.  That takes three clicks.  The fourth click is to collect data.  That's it.  Even a 9th grader could figure it out without instruction - good thing, since I'm teaching 9th grade.  

* Now I'm really showing my age.  I used the Vernier ULI in my classroom back when Things Were Otherwise and the Moon was Different.  I even used the motion detector connected to an Apple IIgs when I was a student.  When I visited Vernier in Beaverton a few years ago, they showed me Dave Vernier's special space where he kept, in working order, every version of Vernier probes and interfaces they've ever made.  I nerded out a bit, showing the same enthusiasm as when my bachelor party walked through the Corridor of Star Trek Artifacts at the Las Vegas Hilton.  Is that Worf's actual bat'leth?  Is that the interface that used a serial port to connect to a PC?

By default, the detector collects for five seconds.  Here's a screenshot of a typical velocity-time collection.  (Switching to position or acceleration is a matter of just two obvious clicks!)  Of course, as is typical with a sonic detector, it missed a point early on - no cart in my classroom was actually moving 18 m/s, i.e. 40 mph or so.  The real motion was captured after about 1.5 s.

I have to teach students to recognize the physical unreasonability of this common graph; then, I have to show them how to zoom in such that they get the output that makes sense.  On a labquest, zooming requires highlighting the relevant part of the graph, followed by two not so obvious clicks.  Oh, and it requires that the touch screen actually works, which is about as likely as an American Airlines flight departing on time.*

* The similarity is striking - just like with AA, the labquest is somewhat likely to have minor maintenance issues, which are not complicated to solve, but no mechanics are available right this instant, so it'll probably have to wait until late tonight.  In the morning, either the labquest/airplane will be working fine, or a replacement will be trundled in.  Fat lot of good that does anyone right now, of course.

But on the app, highlighting and zooming is a breeze.  I use my finger on the phone touchscreen that always works; I hit the magnifying glass button; and voila, the relevant graph shows up - see the screenshot.  The app is so, so intuitive.  Click a point - the vertical axis value shows up.  That's all I care about for basic data collection.

Yes, the app can do far more.  The button in the bottom-left of the screenshot brings up an easy to navigate menu of further analysis options, including slopes and integrals and curve fits and interpolation - it even lets you add your own annotations.  This app contains very powerful tools, tools that can be used for my undergraduate-level research projects.  I rarely need its most powerful tools, though, so I'm glad that the app has simple and useful default settings.  

Now, PASCO makes a very similar product - a compact, bluetooth sonic motion detector.  It works well, too.  I prefer Vernier here not because PASCO is bad, but because the Graphical Analysis app is far more intuitive to me than the Sparkvue app.  You might have a different opinion.  Try them both.  

The good news is, the landscape of PASCO vs. Vernier has changed.  For decades, teachers have had to choose one sensor manufacturer or the other.  The $250 or so per lab station for a Labquest or Capstone interface, plus $100 per probe that only worked with its own interface, meant that the Vernier-Pasco choice was for richer, poorer, sickness and health, till death do us part or the warranty expires.  

No longer!  With the advent of the smartphone-as-interface, now we are able to pick and choose among the bluetooth probes and devices.  For example... PASCO beat Vernier to the punch by about a year with their wireless smartcart.  I bought a classroom set of these.  But now I'm buying Vernier motion detectors, photogates, and force probes - with no sunk costs.  The smartcarts still work great with the free sparkvue app.

The moral is, just buy whatever of these bluetooth probes you like, from whichever manufacturer.  You're not constrained by your past purchases; you're not locking in to your lab's future.