# testing zener diodes

T

#### tempus fugit

Jan 1, 1970
0
Hey all;

I'm trying to test a 5.4 volt zener in a piece of equipment I'm trying to
fix. I've got a Fluke digital meter with a diode test on it. What should the
reverse voltage reading be if it's good? I get around 0.6 in a forward test,
but what should I get in the reverse reading (5.4v)?

Thanks

J

#### John Popelish

Jan 1, 1970
0
tempus said:
Hey all;

I'm trying to test a 5.4 volt zener in a piece of equipment I'm trying to
fix. I've got a Fluke digital meter with a diode test on it. What should the
reverse voltage reading be if it's good? I get around 0.6 in a forward test,
but what should I get in the reverse reading (5.4v)?

Thanks

It should be the same reading you get with an open circuit. Most
diode checkers apply less than 3 volts to an open circuit. You could
apply a small current through the diode by hooking a 9 volt battery in
series with a 1K resistor, and measure the diode voltage drop.

R

#### Ross Mac

Jan 1, 1970
0
5.4 volt zeners are cheap...just swap it out....that's the crude
way...or...if you can power up the circuit...measure the drop!..Not rocket
surgery as they say in the Eggo comercial......good luck...Ross

N

#### norm d.

Jan 1, 1970
0
A simple and reliable method to test a zener is to hook up a simple series
circuit with a voltage a few volts more than the rating of the zener across
the resistor and zener, with the zener in a reverse bias mode. Select the
resistor to limit current to a value less than & no more than the forward
current limit of the device. If the zener works it should force it's rated
value across itself, and the remaining voltage should be dropped across your
carefully selected resistor.

J

#### John Fields

Jan 1, 1970
0
A simple and reliable method to test a zener is to hook up a simple series
circuit with a voltage a few volts more than the rating of the zener across
the resistor and zener, with the zener in a reverse bias mode. Select the
resistor to limit current to a value less than & no more than the forward
current limit of the device. If the zener works it should force it's rated
value across itself, and the remaining voltage should be dropped across your
carefully selected resistor.

---
Well... No.

Since the specified range of the voltage drop across the Zener is only
specified with the _test_ current flowing through the Zener, that's what
should be used.

J

#### JeffM

Jan 1, 1970
0
A simple and reliable method to test a zener
Well... No.
Since the specified range of the voltage drop across the Zener is only
specified with the _test_ current flowing through the Zener,
that's what should be used.
John Fields

I notice that no one has yet said to
disconnect one end of the zener from the circuit.
A shunt path will distort your results
and a short in the load will really screw you up.

T
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