How to properly use this multimeter tool ?

[eh la bas ma]

Hello,

I am trying to read Hfe on several transistors. On my DMM there is a spot to put the transitor's legs and read them, unfortunatly, if the legs are too short it is impossible.

I noticed a little thing in my DMM pocket, looks like it is supposed to read transistors, but I have been unable to read a single one with it. I guess there is certainly something I am doing wrong...

Do you have an idea if this thing can read Hfe, and how am I supposed to proceed ?






Last picture : We can see some little metal terminals inside the holes. Is there a correct orientation with these ?

Thank you very much for your help !

[antonis]

I presume that little thing is for transistor junctions diode measurement..

[GibsonGM]

Maybe the answer is here?

https://btmco.ir/images/EditorUpload/VC97_manual.pdf

[Eb7+9]

Do you have an idea if this thing can read Hfe, and how am I supposed to proceed ?

... are you serious ??

[FiveseveN]

... are you serious ??

To expand a bit... You need 3 connections to measure hFE, but a multimeter only has 2 probes.
Use the included tool (the round thing) with new transistors or an adapter with longer pins. Or build your own circuit to characterize the transistors.

[eh la bas ma]

Thanks for your replies !

I won't waste anymore time trying to read Hfe with this. Maybe it will be useful one day...

I'll try longer pins in the DMM holes.

Or build your own circuit to characterize the transistors.

What kind of circuit would you suggest to do that ?

[Hairstyle]

I have one of those socket things that came with my cheapo DMM too. It does give me a number if i stick a transistor in it but i don't think i would use it to accurately measure or match transistors, just to get a rough idea of the hfe. Have your transistors had their legs trimmed off or something? I've stuck anything from a 2n3904 to a metal can to germanium, npn or pnp, and always got a reading. Sometimes you do have to wiggle the transistor a bit, the contacts inside aren't the tightest. Also beware of the pinout of course.
Good luck!

[m4268588]

Simplified Quick Measurements

[antonis]

Just make sure for Rb to be much bigger than expected h_FE times Rc..
If not, BJT is saturated and there is no DC current gain sense anymore..

P.S.1
It should be a good idea for h_FE measurement for particular BJT circuit appication Collector working current..

P.S.2
Needless to highlight that any circuit based on h_FEs is a badly designed circuit..

[Phend]

As m4268588 says.
This works,  select resistors in series to get need values.
DMM with those holes in a circle,  na.

http://www.geofex.com/article_folders/ffselect.htm

[deadastronaut]

off topic, but meter related, my old meter has decided to ''beep'' on continuity setting

even when the probes aren't even attached...wtf. 

put a new battery in, still the same...thoughts?

[antonis]

What's the reading on resistance mode..??

[GibsonGM]

Rob - fuse ok? Battery?    Mine goes batty if I measure current and blow 'that' fuse (maybe while doing automobile work), but it still works for other functions - with glitches...HTH

[deadastronaut]

What's the reading on resistance mode..??

aha...you got it, naff all. 

is it the fuse then ?..

[GibsonGM]

Seems it could be...take it out, see if it 'beeps'!   That's always the case when my Extech goes off.

[deadastronaut]

aha, found the culprit...

there is a silver piece of ally in there as a shield, and it slipped down and was touching the piezo..

the bugger...

cheers guys...back to beeping when requested again...

as you were..sorry for the hijack. 

[anotherjim]

It's my experience that cheap DMM's like this yellow peril...

Have far better transistor test sockets than more expensive ones where the contacts are too low down.

[Grunfeld]

I have a similar attachment for my DMM.
I used it to try and match some silicon transistors and got  readings of around 170 hFE on a batch of 2n3903s that I bought, which doesn't seem right because their data sheet lists the max gain at 150.
https://www.onsemi.com/pdf/datasheet/2n3903-d.pdf

Can anyone explain what's going on there?

At the same time I also got readings of 190-200 for a batch 2n3904s, which makes sense to me.

[idy]

Gain varies by current. There is not one number, but a curve, with a hump. Your meter is using a different current than the data sheet did for their minimum.

The corollary to this is that real engineers learn to design circuits to not be too finicky about the gain of the devices.

[Grunfeld]

Gain varies by current. There is not one number, but a curve, with a hump. Your meter is using a different current than the data sheet did for their minimum.

The corollary to this is that real engineers learn to design circuits to not be too finicky about the gain of the devices.

Does that mean that I can trust in the relative measurements between different transistors on my meter? I.e. for determining the ratio between transistors.