"Michael Karcher" wrote in message
...
Arfa Daily wrote:
I have always preferred an 'old fashioned' 20k ohms per volt analogue
multimeter - in my case an AVO 8 MkIV. Digital meters can give very
misleading resistance readings across transistor junctions.
That's why even the chepest digital multimeters have a "diode test"
mode that measures the forward voltage at 1 to 4 mA (depending on
the multimeter, check the manual). Low-power-transistors should read
about 600mV B-E and B-C, and open circuit C-E.

Regards,
Michael Karcher

Yes, Michael, I've been in the service business long enough to understand
the differences between a digital DMM and its diode test facility. However,
it's not at all uncommon to get unstable readings, particularly if you are
measuring 'in-circuit', and significant (in terms of actual digits)
differences between two equally good devices. Even the temperature of your
fingers can cause the digits to shift, as can the long cooling down period
if the device has just been unsoldered from a board. And of course,
differences between different categories of device.

When training others, I have found that this can give rise to confusion in
students, who expect to see 'absolutes' on meters with digital readouts. An
analogue meter used for this purpose gives a simple go / no go on a junction
that in my experience, is a better than 99% indicator of a good or faulty
device. The OP said at the start that he was a self-trainer in electronics
service. He actually stated in one post that measuring the junction
resistances in-circuit, resulted in a different reading every time. This is
typically what you find when using a digital meter. Often, in these cases, a
good old analogue meter will give a stable and consistent reading, which
will allow you to make a sensible evaluation. This was the point that I was
trying to make to the OP.

Arfa