SCHOTTKY DIODES SILICON, GERMANIUM

SILICON, GERMANIUM AND SCHOTTKY DIODES
When testing a diode with an analogue meter, you will get a low reading in one
direction and a high (or NO READING) in the other direction. When reading in the LOW
direction, the needle will swing nearly full scale and the reading is not a resistancevalue
but a reflection of the characteristic voltage drop across the junction of the
diode. As we mentioned before, a resistance reading is really a voltage reading and the
meter is measuring the voltage of the battery minus the voltage-drop across the
diode.
Since Silicon, Germanium and Schottky Diodes have slightly different characteristic
voltage drops across the junction, you will get a slightly different reading on the scale.
This does not represent one diode being better than the other or capable of handling a
higher current or any other feature.
The quickest, easiest and cheapest way to find, fix and solve a problem caused by a
faulty diode is to replace it.
There is no piece of test equipment capable of testing a diode fully, and the circuit you
are working on is actually the best piece of test equipment as it is identifying the fault
UNDER LOAD.
Only very simple tests can be done with a multimeter and it is best to check a diode
with an ANALOGUE MULTIMETER as it outputs a higher current though the diode and
produces a more-reliable result.
A Digital meter can produce false readings as it does not apply enough current to
activate the junction.
Fortunately almost every digital multimeter has a diode test mode. Using this, a
silicon diode should read a voltage drop between 0.5v to 0.8v in the forward direction
and open in the reverse direction. For a germanium diode, the reading will be lower,
around 0.2v - 0.4v in the forward direction. A bad diode will read zero volts in both
directions.