If you are an electronics hobbyist then AVR Transistortesters are the greatest thing since sliced bread! Why if Ron Popiel was still alive he'd be hawking these night and day on the Shopping Network. But sometimes there is such a thing as too much of a good thing. Sorting through the myriad of offerings out there now can be daunting. That is where I hope my guide will come in handy.

Step 1: Oh How Bad Can It Be?

Forget about it! Go here and see for yourself

http://www.aliexpress.com/wholesale?catId=0&initia...

There are pages, and pages of these things. All similar, but different. The Devil is in the details with these units. It is the details that I plan on highlighting here too.

Step 2: The Back Story

Or what I didn't know when I bought my first meter.

It turns out all of these meters are variations on an open source project created by some German hams.

http://www.mikrocontroller.net/articles/AVR_Transi...

That is in German, so unless you can read German it is not too helpful. They have a PDF manual for us English language speakers.

http://www.mikrocontroller.net/wikifiles/8/8f/Ttes...

This applies to various degrees depending on which Chinese version you get. But the more it applies the better off you are. Which is where my guide hopefully is going to help with.

Step 3: What You Need to Know

OK you already know more about these meters than I did when I bought the first one I have. But I am going to try to briefly sum up the salient information we all need to be aware of here.

The main differences between all of these meters is how they generate their reference voltage, and their display screen. In my graphic for this step I took screen captures of data sheets for a Precision Voltage Reference, and a Zener diode. Because these meters use one, or the other as their reference. The really cheap meters use the Zener diode, and better ones have the Precision Voltage Reference device. You of course want to get a Precision Reference, and not a Zener diode.

The first meter I bought only has a Zener diode in it. Because I did not know any of this. Score one against me. But I quickly found out about this, then I bought my second meter that has a Precision Reference in it. Then I saw a meter with a Graphical Display, and a Precision Reference. I was like all that and a bag of chips! So of course I bought one of those as well.

I must say the last meter I bought is the deluxe model. It is far and away head and shoulders above the other two in the way of features. In my opinion it is the one to get. Considering that I had to go on such an odyssey to get that one I figured I'd post this article. Just to save others from all I ended up going through.

Step 4: But Wait, There's More!

OK you know which meter to get now but there is more to these meters than just that. There are things to know. This I suppose is the guide section of this article. Now I'm obviously pretty into these particular meters. I mean heck, I got 3 of the things. I have read all of the dense nonsense about them too, so you don't have to!

Also in the course of my research I have viewed a number of Youtube videos showing various people and their impressions, and or experiences with these meters. I have noticed that a number of individuals apparently do not know what their meters are capable of doing. I saw one fellow in fact that wanted to test the accuracy of his meter. But he failed to calibrate it first. Duh!

Let's be real here, the Chinese are cranking these out like mad, so they're not spending the time to calibrate them before they ship them out the door. In any event if you are really concerned about accuracy then you should run through the calibration sequence yourself anyways. It is just due diligence.

So how do I calibrate the meter you may ask? It could not be easier to do. Just connect all 3 test leads together, then press the "Test" button. Yup, pretty easy. Pretty easy if you know about the feature at any rate. When the meter notices it is shorted out it will ask you if you would like to enter Self-Test mode. You need to have a quality capacitor above 100nF to complete the calibration routine. Past that you simply follow the prompts.

Some meters with the proper firmware in them also allow access to calibration mode from the features menu. I will talk a little about the features menu in the next step.

Step 5: The Features Menu

I don't know if that is what this is really called, but it is what I'm calling it here. OK so what is the "Features Menu"? Where is it? You call up the features menu by pressing, and holding the test button down. Hold the button down long enough and it should pop up. Now my first meter only has one item in its features menu, a screen contrast adjustment.

"Real" AVR Transistortesters have a fairly rich features menu built into them though. If truth be told it is all not particularly useful, but heck it's there, so you might as well at least know about it. I certainly played with it myself when I first got my meters. Hooked it up to my scope, etc. Stuff works.

I've already mentioned that Self Test should be in the menu someplace, and related to that is display data. The data is your saved calibration settings. There is also a frequency generator, and a PWM generator too. Plus some other things that I am not entirely sure right now precisely what they are. But it is there, so play around with it yourself, and see what you can make of it all.

I am showing bits of the menu in my Graphical Display meter because it does the menu the best. The Test switch is also a rotary knob too. Turning the knob scrolls through the display. It is nice.

I guess I'll add a link to my favorite meter. I am not affiliated with the seller, and receive no compensation, blah, blah. This is only for information purposes and whatever other disclaimers you can think of.

http://www.banggood.com/DIY-M12864-Graphics-Versio...

It is a kit, so you have to assemble it. But I really like this one myself.

This concludes my AVR Transistortester Guide. As always leave comments, suggestions, and feedback, hate messages, or whatever in the comments. It's all good!