How to check transistor E, B, C with multimeter ?

[learner1]

Hi all,

Does anybody know how to check the transistor emitter, base & collector with multimeter ? Sometimes I can not get the datasheet of transistor.

thks.

 

[Someone Electro]

It shodnt conduct from E to C bouth ways

IT shod conduct from B to E an C one way (wich way depends on the transistor type)

A lot of multimeters hve the tranistor test function.That also displays its gain

 

[eblc1388]

It shodnt conduct from E to C bouth ways

IT shod conduct from B to E an C one way (wich way depends on the transistor type)

A lot of multimeters hve the tranistor test function.That also displays its gain

But which is the C pin and which is the E pin that learn1 wanted to know?

 

[monkeytree]

is pin B always in the middle?

 

[Nigel Goodwin]

It shodnt conduct from E to C bouth ways

IT shod conduct from B to E an C one way (wich way depends on the transistor type)

A lot of multimeters hve the tranistor test function.That also displays its gain

But which is the C pin and which is the E pin that learn1 wanted to know?

You can't test for that very easily, as you know transistors are either NPN or PNP, so in either case the collector and emitter are both the same (either N or P).

Transistors will work either way round, generally you should get higher gain with the collector connected correctly, but it's quite common practice to connect them the same way sometimes, as this gives a lower Vce drop - mute transistors are often wired that way!.

So assuming you can check their gain?, assume the way that gives the highest gain is correct!.

The connections can be various ways round, the most common are base in the centre, or collector in the centre.

 

[eblc1388]

The connections can be various ways round, the most common are base in the centre, or collector in the centre.

I never understand why for a small TO-92 transistor, manufacturers would choose to swap the pins around. I always hated to check before use for every TO-92 I picked from my junk box because I'm not sure which pin is which.

Why can't they just stick to one pin configuration, like the TO-3 or TO-39. :cry:

 

[Someone Electro]

I hate that too

 

[zevon8]

The only reason I can think of for different pin order is to allow easier connections on PCB's , especially when densly packed, or connecting transistors in push-pull. Sometimes it helps with keeping all the transistors physically facing the same way, yet have different lead arrangements.

 

[Morgen]

How to check the transistor emitter, base & collector with multimeter:
1. Using an ohmmeter, measure the resistance between each pair of transistor terminals. The two lowest values are from base to emitter and from base to collector. This identifies the base terminal.
2. Whether the transistor is PNP or NPN is shown by the polarity of the meter test leads in measurement of forward resistance.
3. Apply the ohmmeter test leads to the collector and emitter terminals of the transistor (which is C and which is E is unknown at this time).
4. Pinch the base lead and one of the other leads between the thumb and forefinger to provide "bleeder resistance." Note the resistance reading.
5. Pinch the base lead and the remaining other lead between the thumb and forefinger to provide "bleeder resistance." Note the resistance reading.
6. Reverse the ohmmeter leads and repeat steps 4 and 5.
6. The collector is the terminal that provides the lowest resistance reading when its test voltage is "bled" into the base terminal.