Electronics      Reviews, Teardowns, & Guides

Introduction


One day I noticed this cool-looking mini oscilloscope.  It's basically a circuit board with a TFT LCD screen on it:  oscilloscope-on-a-board.

For the low price, I figured it was worth a try.



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In This Article

Unboxing

Instructions

Power On

Input Impedance

Input Voltage

Basic Test

Granularity

Other Stuff

Try This

Conclusion



Unboxing


It was packaged in an anti-static bag. 

You can buy this scope either in kit form or assembled.  I got the assembled one. 

The unit has two circuit boards, one of which has the TFT LCD.  Shown here, the lower circuit board without the LCD screen:




In the package there was also the test probe and a couple folded instruction sheets.


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Instructions


Very good.  There's a schematic and a full-color guide that shows each component type. 

The instructions include a troubleshooting flowchart and a list of test-point voltages.  Excellent.

Assembling the unit from kit-form will require you to have soldering skills already.


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Input Impedance


1 Megohm. 

If you wanted to upgrade to a 10x probe, any standard "20 MHz" 10x probe should work without issue.  It's the higher-frequency scopes that start to need the more sophisticated ones.


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Input Voltage


For the device under test:

50 Volts peak-to-peak, max (1x probe) 

400 Volts peak-to-peak, max (10x probe). 

The probe supplied with the unit is 1x.  Don't use a 1x probe to test mains voltage or tube amps;  you'll need a 10x probe.


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Power On


This will require a benchtop power supply.  I prefer linear supplies;  this one is actually very good for the money.  Or, try this one.  Set it to 9 volts DC.

There are two ways to connect it.  You can use a two-pin header like you'd find on a computer board (which it basically is); or, you can use a standard center-positive barrel connector.  I just happened to have the right size connector; didn't measure it but I should probably update this with the diameter.

The o-scope goes through a couple of quick boot-up screens, and then you should see the proper oscilloscope grid. 

Current draw is about 140 milliamps.


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Basic Test


If you're in a building, chances are you've got a 60Hz AC signal.  Not the building;  you.  The human body may have as much as a volt or three at 60 Hz.

Most RF noise is in the microvolt range, so this oscilloscope won't detect it (or will it?  Stay tuned.)  But the 60 Hz "air signal" will be anywhere from millivolts to a volt.  You can easily read that on this unit.

At 60 Hz, each complete cycle is 0.0167 second.  That is about 17 milliseconds.  Keeping that in mind, study that picture at the top of the page again.  When each major grid line is 5 milliseconds, you can see that a complete sine wave is 17 milliseconds.  So there's the 60 Hz wave.  (And it looks like 4 volts peak-to-peak... wow.)


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Granularity


There are 9 different voltage ranges for the display.  It uses a fairly standard 1-2-5 multiplier sequence.  When you combine that with the other three adjustments (1V, 0.1V, and 10 mV), that gives you all the different ranges.  So that's pretty good.

There's no "fine adjustment" from what I can see.  (Obviously it can't replace something like this.) 

The time-base has a total of 24 different settings, again using a 1-2-5 sequence.  The range limits are 10 microseconds to 500 seconds.  500 seconds... if you were troubleshooting a digital clock, that would let you detect some of those voltage signals to the LED tiles.  You could at least check the 1-minute tile, and sort of the 10-minute tile.

And the 10 usec time base... you'll need that for the higher frequencies (up to 200 kHz.)


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Other Stuff


The acrylic case (might be sold seperately, depending on the seller) was a project I decided to leave for another time.

For now, I'm just using this as an oscilloscope-on-a-board.  The main thing is to keep from zapping it with static electricity.  This is why it's smart to keep a grounded metal plate attached to the side of your bench.  De-energize periodically with it.


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Try This


Here's a fun thing to try.  Set the time base to 50us and the voltage to 10mV AC.  Pick up the GND lead and let the other lead free in the air.  Move it around until the red lead hovers over the oscilloscope board.  If you do this right, you should see a definite waveform.

One complete cycle looks like about 65 microseconds to me. 

65 microseconds is about 15.38 kHz.  As I move the oscilloscope leads, the amplitude goes highest over the middle of the TFT display.  Here it looks like about 36 or 37 millivolts.  (Press the OK button for HOLD, which will store the waveform.  Then you can use the grid to measure the wave characteristics.)




When the red lead is over the dead-center of the TFT display, the signal is loudest.  It's originating from the display.  This unit shows it to be loud, but actually it's nothing compared to my computer screen.

Sure enough, this oscilloscope can pick up the 200 kHz RF noise from my computer monitor.  (Time base: 10 microseconds.)  200 kHz is the limit of detection.  The amplitude seems much lower on the 'scope because the test leads don't pick it up well, for a couple of reasons.  (But a LW radio picks it up loud and clear;  it's loudest at 192 kHz.)

Fun stuff.  I like this little oscilloscope.  Try this link to get yours.


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Another Cool Thing


Sure, it would be better if it were 10 MHz or something, but there's actually a lot you can do with a 200 kHz oscilloscope.  Look for audio-frequency AC hum, bad filter capacitors, ground loop contamination, all sorts of stuff.  A lot of the things you'd look for in an audio amplifier are well under 200 kHz.  If you're building the basic low-cost electronics bench, you need one of these.

Let's say you have a mini stereo system and you keep hearing speaker hum.  Test the RCA or speaker connectors and see what the oscilloscope finds.  Check each site with a multimeter first (just to make sure there's not enough voltage to fry your scope).  Then scope it with this. 

The basic digital storage feature lets you catch one-time events, if you're quick.  Such as, look for a voltage transient when you turn off your favorite bench power supply.  I still have to test mine for this. 


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Conclusion


It's a fun little gadget that's actually a real oscilloscope.  With a bandwidth of only 200 kilohertz, it's primarily for audio-frequency work.  You could also use it for Arduino and that type of thing, I would guess.

There are many times it's necessary to measure low-frequency AC in electronics.  Test audio stages or RF stages for 60 Hz and its harmonics.  Lots of possibilities here.  Also, a unit like this is certainly more expendable than a Rigol or Tektronix, so that could be an advantage as well.

It's also a good learning tool;  there are fewer buttons and switches than on a benchtop scope.

For the price, yep I'd get one.  Try this link for the assembled version. 



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