HOW TO TEST ZENER DIODE
by digital multimeter and Analog multimeter
ZENER DIODE TESTING Zener diode is a subtype of a diode and it use on circuit as a different function from standard diode. Standard diode we use it as forward bias mode but for Zener diode we use it as reverse bias mode on circuit. When applying forward bias to zener diode it will conduct and let current flow as standard diode , another condition when applying reverse bias to zener diode it will not let current flow until the voltage supply is over the zener breakdown voltage then it will let current flow.
Basic Circuit of zener Diode
How to check zener diode , it has more detail then checking standard diode as it is a subtype of diode so in some condition checking method is as same as standard diode. Before checking you have to know important technical detail of multimeter. We set analog multimeter to range Rx1 or Rx10 , let consider at the test lead there is 3VDC 150mA for Rx1 range and 3VDC 15mA for Rx10.
There is 1.47VDC at the test leads of Diode Test Function of Digital mulimeter(some model)
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Test IGBT Part 1
1. Turn rotary switch of digital multimeter to Diode Function test.
2. If zener diode has zener breakdown voltage above the lead test voltage .
( We use Digital mulimeter that has 3.28VDC at test leads)
2.1 If it is a good zener Diode it will show voltage drop across diode when applying forward bias.
and show "OL" when applying reverse bias.
2.2 If it is a BAD zener Diode ( Open) , it show " OL" on both forward bias and reverse bias.
2.3 If it is a BAD zener Diode ( shorted ) , it show very small voltage drop on both forward bias and reverse bias.
3. If a zener diode has zener breakdown voltage below the lead tests. we use Digital mulimeter that has 3.28VDC at test leads.
3.1 When applying forward bias to zener diode it will let current flow and there is voltage drop across it around 0.4-0.7V and when applying reverse bias to zener diode it will let current flow too as voltage magnitude from the test leads is over zener breakdown voltage , for example 2.7V zener diode , it will display 2.7V when applying reverse bias.
3.2 If it is a BAD zener Diode (open) , it show " OL" on both forward bias and reverse bias.
3.3 If it is a BAD zener Diode (shorted) , it show very small voltage drop on both forward bias and reverse bias ( such as 0.002V).
Step to c heck Zener Diode with Analog multimeter.
1. Turn the rotary switch of analog multimeter to Rx1 test Function.
2. If a zener diode has zener breakdown voltage above the test leads voltage. We use Analog mulimeter that has 3.1VDC at it's test leads.
2.1 If it is a good zener Diode it will show low resistance around 3-10 ohm when applying forward bias. and pointer point at ∞ resistance scale when applying reverse bias.
2.2 If it is a BAD zener Diode ( open) , pointer point at ∞ Infinity resistance for both forward bias and reverse bias.
2.3 If it is a BAD zener Diode (shorted ) it show 0 ohm resistance for both forward bias and reverse bias.
Good Zener Diode has low resistance around 3-10 ohm when applying forward bias.
Good Zener Diode has ∞ infinity resistance when applying reverse bias.
Shorted zener Diode has 0 ohm resistance for both forward bias and reverse bias.
3. If a zener diode has zener breakdown voltage below the test leads voltage (for example ZD = 2.7V) . We use analog mulimeter that has 3.1VDC at it's test leads.
3.1 when applying forward bias to zener diode it will let current flow and there is low resistance around 3-10 ohm and when reverse bias to zener diode it will let current flow too as the voltage at test leads is over zener break down voltage so current flow and there is some low resistance ( but resistance is not as low as shorted case 0 ohm)
3.2 If it is a BAD zener Diode (open ) , pointer point at ∞ infinity resistance scale for both forward bias and reverse bias.
3.3 If it is a BAD zener Diode (shorted) , pointer point at 0 ohm resistance for both forward bias and reverse bias.
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