Electronics > Beginners

MultiMeter

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rstofer:
On the theme of equipment, I would suggest you at least consider the capabilities of the Digilent Analog Discovery 2.  This one gadget has a 2 channel Arbitrary Waveform Generator, a two channel Oscilloscope, a dual output power supply, 16 channels of digital input/output with protocol decoding and a lot of other features.

I have the feeling that a lot of folks just blow off this recommendation.  In my view for LEARNING electronics, there is nothing like it.  Every tool I need in a small, breadboard friendly package.  Maybe it is suboptimal for tinkering and I'll concede that when I want to see some arbitrary waveform, I might use my scope(s) but if the intent is to breadboard small circuits, there is no tool on the planet that comes close.

Read over the Features list and download the free Waveforms software.  There is a "Demo" device that will allow you to exercise the various features.  There are a lot of videos on YouTube and they are probably worth watching.

The problem is, it's expensive by the time you get it kitted out.  Heck, it starts out expensive even when just bare bones!  You can delay some of the add-ons and just use it the way it comes.  Or, think about buying 2 or 3 Breadboard Adapters.  You can then build up an experiment per breadboard and keep them assembled for a while.  The other stuff, like the BNC adapter and scope leads can wait.  BTW, you lose the differential input capability of the AD2 when you add the BNC connectors.  The shell of the BNC connector will be connected to earth ground through the PC - if the PC is grounded.  Be careful here!  I don't tend to use my BNC adapter very often but I have other scopes.  YMMV on this...

https://store.digilentinc.com/analog-discovery-2-100msps-usb-oscilloscope-logic-analyzer-and-variable-power-supply/

https://store.digilentinc.com/breadboard-adapter-for-analog-discovery/

Look in EveryCircuits -> Examples -> RC Step Response  I like to build this circuit with a 10k resistor and a 0.1 ufd capacitor.  I then hit it with a square wave (offset such that the voltage swings between 0V and, say, 1V) with about a 12 ms period.  That leaves 6 ms high and 6 ms low and since the time constant Tau = R*C = 1 ms, I get 6 Tau high and 6 Tau low.  We know from 1-e-6 that we are 99.75% of fully charged/discharged in 6 * Tau.  Experiment!  Cut back to 3 Tau or stretch it out to 10 Tau.  Exercise your calculator to figure out the percentage of full charge.

The EveryCircuits video on the home page of their web site deals with this very circuit around 2:30  In the Example they settle on 5 Tau.  Fair enough but it's only 99.33% charged.

I can spend an entire morning with just these two parts and the AD2.  We know from ELI the ICE man that the current leads the voltage in a capacitive circuit and that it leads by 90 degrees.  Prove it!  You measure current using the differential input feature of the AD2 scope across the resistor (differential connection) and voltage across the capacitor on channel 2.  See attached  PhaseShift.png.  The yellow trace is current through the resistor (by measuring voltage across the resistor) and the blue trace is capacitor voltage.  You can see that the yellow trace leads the blue trace by 90 degrees - exactly what ELI the ICE man predicts.

https://www.khanacademy.org/science/electrical-engineering/ee-circuit-analysis-topic/ee-ac-analysis/v/ee-eli-the-ice-man

Or maybe you just want a Bode' Plot of the RC filter - see BodePlot.png  Note how the -3dB point occurs at 1/(2*pi*R*C) - I'm telling you, this stuff is magic!

See the section Cut-off Frequency and Phase Shift here:
https://www.electronics-tutorials.ws/filter/filter_2.html

I could go on for pages about this tool.  It really is the best thing around for learning - maybe that's why so many universities have adopted it.

I could put on a fairly long class using just those 2 parts and the AD2.  Wait until we get to transistors!

Alas, there is a difference between "learning electronics" and "tinkering with electronics".  The AD2 is more aligned with "learning electronics".  See the "Real Analog" course at Digilent.

A 27" scope screen is pretty cool!

ETA:  I added the AD2 plot of the forced response example discussed above.  10k Ohm, 0.1 ufd, Tau = 1 ms

AVGresponding:
I would add that you should not rule out purchasing used, higher quality equipment.

All of my higher end gear is used, I reckon I've spent less than $1500, and have what would cost ten times that to buy new.

The Products section include many threads on test gear, the TEA (Test Equipment Anonymous) thread is in fact the most popular thread on the EEVBlog forums!

There's certainly plenty of advice to be had on finding, buying, and repairing this kind of gear.

rstofer:
But the question is, can a beginner with essentially no skills or equipment actually fix anything that is defective?  And they need to know which pieces of gear can't be fixed at all.  Like those Tek scopes with unobtainium ICs.  And how many times has the statement been made that "you need a working scope to repair a defective scope".  Maybe you do, maybe you don't, but if you do and don't have one you're in a heap of trouble.

I bought my two bench meters and my Tek 485 from eBay and all 3 have been perfect.  But I didn't want another CRO, I wanted a DSO and they aren't particularly cheap on eBay.  The bench meters were cheap because of the dumping from that pay-to-learn college.  If they hadn't been cheap, I wouldn't have bought them.

In my view, buying used is a tremendous risk given the presumed lack of skills of the purchaser.

I might consider a power supply but, in spite of my outcome, I wouldn't recommend a scope unless it was recently refurbished and calibrated.  Unfortunately, these don't tend to be cheap.

AVGresponding:
Perhaps I should have added "if necessary".

None of my gear has required anything more than minor repairs, and most of it hasn't needed repairing at all.

As for a scope, my main one is a TDS420A with all the options which I got for £90 shipped, and with 7 top quality probes included. It's old and out of date compared with modern stuff yes, but it's more than capable for my purposes. I'll eventually have to replace the NVRAM batteries of course, but for now they still have plenty of juice.
I have a Hameg 203-6 as well, useful for its component tester, and even though it's only a 20MHz 2 channel jobby, that's probably all a beginner would need. I paid £50 shipped iirc. A couple of the pushrods that connect internal switches to the front panel needed fixing is all.

I'd say that a DE-5000 is overkill for a beginner, those cheap Atmel 328 based component testers for around £5-10 are close enough; I have one and it's not a million miles away from a £2000 (if I'd bought it new   ;)  ) LCR meter I recently acquired.
Another advantage those have is their ability to identify type and pinout for most transistors and diodes, though I wouldn't trust the hfe readings.

I'd go so far as to say those little 328 based gizmos are an essential part of any EE toolbox, pro, am, or novice.

rstofer:
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR1.TRC0.A0.H0.Xtds420a.TRS0&_nkw=tds420a&_sacat=0

That TDS420A is priced all over the map at eBay.  Some for a couple of hundred bucks and some for nearly a couple of thousand.  That's it's 4 channels and 200 MHz makes it very useful for the hobbyist but they first need to sort out the difference between the $200 versions and the $2000 versions.

While the TDS420A is 'digitizing', I'm not sure how it compares to a modern DSO.  These new fangled scopes do everything!  I bought the DS1054Z primarily to do decoding of SPI (without having to drag out my logic analyzer) and it works well for microcontroller projects.

The measurement capabilities of the modern DSO make it far more useful than a traditional CRO.  My 350 MHz Tek 485 is still here because it has bandwidth.  There's no way I would want to buy a DSO with similar bandwidth.

In any event, these are choices for the newcomer to make.  There are some old-dog scopes around that are perfectly adequate for those just starting out.

eBay has the DS1054Z for a couple of hundred bucks more that Amazon!

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