From: rob@despammer.com   
      
   On 04/03/2020 19:22, Ralph Mowery wrote:   
   > In article , rob@despammer.com says...   
   >> have some BC547 transistors which I want to use in a circuit, but   
   >> according to this:   
   >>   
   >> Hook the positive lead from the multimeter to the to the EMITTER (E) of   
   >> the transistor. Hook the negative meter lead to the BASE (B) of the   
   >> transistor. For an good NPN transistor, you should see ?OL? (Over   
   >> Limit). If you are testing PNP transistor, the meter should show a   
   >> voltage drop between 0.45V and 0.9V.4 May 2017   
   >>   
   >> None of the BC547's give the those readings, as I get 0.02V on a few of   
   >> what I have, and not 0.45V.   
   >>   
   >>   
   >   
   > If you are seeing .02 v it is as if the transistor is shorted.  Try   
   > testing in both directions with the meter set as an ohm meter.  I assume   
   > you are using a digital meter which usually will not have enough   
   > current/voltage  to bias the transistor into conduction.  It will   
   > probably show shorted or very near zero ohms in both directions.  An   
   > analog meter will usually bias the transistor into conduction so it will   
   > show low resistance in one direction and if the leads are reversed , a   
   > high resistance.   
   >   
   > Seems that you are using the meter like a diode tester.  That is fine.   
   >   
   > For any type of a a bipolar transistor  put one lead on the base.  Then   
   > put the other lead on the emitter, then the collector.  It should show   
   > around .2 to .4 volts if the older germanium and .6 to .9 if silicon.   
   > Then reverse the leads and do the same .  The meter should show an open   
   > circuit  or OL .   Then put the leads on the emitter and collector.   
   > They should show open OL on in both directions.   
   >   
   > A common transistor will test like 2 diodes in series or back to back   
   > with the base as the common connection point.   
   >   
      
   The meter I am using is an old Fluke77 digital from RS about 30 or 35   
   years ago, and I have tried x5 BC547 tansistors.   
   Using the voltage selection, I get 0.0v with negative lead on the   
   collector and positive on the Emitter, and swapping round I get 0.25v   
   Using the Ohm selection, I get OL in both directions, and the same using   
     the diode selection with the negative lead on the base of the transistor   
      
   I don't have an analogue meter now.   
      
   Thanks   
      
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