What do they do? Is it to test transistors to see if they match and such?

 

Yes, it's for testing transistors. You can use the slots to figure out whether it's an NPN or PNP transistor, which leads are E, B, C, and what the approximate gain (hFE) is at some fixed current (low current, in the mA range).

 

It is to test the hFE of a single transistor. They provide 4 connections to the 3 leads on the transistor so that you will be able to match any of all the possible different pinouts of transistors.

edit: (Almost beat Wookie this time... but not quite.)

 

Whats the hFE?? And I don't get how to use them...the slots are smaller than the transistors' pins so how would I be able to connect it to test?

And how would you know if its an NPN or PNP by using it??

 

hFE is "the small signal forward current gain of a bipolar junction transistor".
It's often abbreviated simply as "gain".

If your transistors' pins are too large for the slots, then you will need to use some wire jumpers.

To start off with, you look up a datasheet for the transistor. They usually have the transistor terminal connections documented in some fashion. Then try that combination and see if it works (you get some positive number greater than 5 on the meter display).

If you can't find a datasheet, then just try every combination of the three terminals, on both the PNP and NPN sides.

 

Hello,

The following table has the basic parameters for a lot of transistors:
transistor_tabel.xls.zip
Just unzip it and load it in excell or OOOcalc.

Bertus

 

I understand that hfe is "small signal AC current gain" and hFE is DC current gain.

 

So how can I find out if two transistors are "matched" using my multimeter? And also, which setting do I dial my multimeter to to even test this thing on? The resistance, voltage, or current?

 

Turn the dial on the multimeter to "transistor test" or something similar.
Plug in a transistor with its pins according to the label on the multimeter (look at the datasheet of the transistor to see which pin is which) and record the hFE number. Then plug in more transistors and do the same.

When you have two transistors with the same or similar number then their hFE are matched at that tested current.

 

But there's no writing on my this stupid cheap multimeter I have...which symbol is for "transistor test"? There's a whole bunch of symbols but I'm only familiar with mainstream voltage, current, ohms, and a couple others but that's all.

 

But there's no writing on my this stupid cheap multimeter I have...which symbol is for "transistor test"? There's a whole bunch of symbols but I'm only familiar with mainstream voltage, current, ohms, and a couple others but that's all.

Post a clear photo of the front of your multimeter.

 

Your meter should have two switch positions marked NPN and PNP.

 

I have seen some meters with a single switch position marked hFE, the meter being provided with separate socket positions for NPN and PNP transistors.

It seems very strange though if the meter has no markings - perhaps they have worn off, or are in a foreign language (Chinese?).

 

Meter should have a roatary position for \(H_{FE}\), usually hidden around the diode check/continuity.

Some meters only have 3 pin sockets, unlabled, and will auto identify (NPN, PNP), show pin out (EBC, CBE, etc), then show gain, giving about 1 second to each display and cycling through them until you remove the transistor.

 

It is marked with a hFE sign. Rotate your Multimeter’s pointer and make it point toward hFE sign. Then put the transistor in the according space and you will get the beta value at display.

Also, the only way the hFE test could be useful is that you check the hFE for each transistor (the parameters of your multimeter are ok) before and after your experimentation, if you get a very different value probably your transistor is fried.

 

Ok thanks guys! Thank you!

 

So, which meter do you have? What marking is on the meter?

 

http://www.kpsec.freeuk.com/components/tran.htm
http://www.youtube.com/watch?v=YsJXFLnA62s

 

Thanks but I already have figured it out. I have an hFe marking on my multimeter but it doesn't seem to work...it just displays 0.00 for any transistor I use anyway so I dunno, maybe its my transistors that are crappy (I'm testing TIP29C, TIP30C, MJE172, and MJE182's).