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Am I testing diodes properly?

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1

$begingroup$

I decided to test some diodes that I have, using a multimeter to measure their forward bias voltage. I set my multimeter to voltage test and connected the diode across:

I tested a bunch of different diodes, both germanium and silicone type, so I expected to see voltages around 0.2 - 0.7V. However, all diodes showed 0V!

I tried reversing the polarity of the diodes, as well switching multimeters. Always my measurement came out as 0V. So am I making some kind of mistake in measuring diodes, or are both of my multimeters/all diodes broken?

diodes multimeter

share|improve this question

asked 8 hours ago

S. RotosS. Rotos

1,03522 gold badges99 silver badges1818 bronze badges

$endgroup$

add a comment | 

1

$begingroup$

I decided to test some diodes that I have, using a multimeter to measure their forward bias voltage. I set my multimeter to voltage test and connected the diode across:

I tested a bunch of different diodes, both germanium and silicone type, so I expected to see voltages around 0.2 - 0.7V. However, all diodes showed 0V!

I tried reversing the polarity of the diodes, as well switching multimeters. Always my measurement came out as 0V. So am I making some kind of mistake in measuring diodes, or are both of my multimeters/all diodes broken?

diodes multimeter

share|improve this question

asked 8 hours ago

S. RotosS. Rotos

1,03522 gold badges99 silver badges1818 bronze badges

$endgroup$

add a comment | 

$begingroup$

I decided to test some diodes that I have, using a multimeter to measure their forward bias voltage. I set my multimeter to voltage test and connected the diode across:

I tested a bunch of different diodes, both germanium and silicone type, so I expected to see voltages around 0.2 - 0.7V. However, all diodes showed 0V!

I tried reversing the polarity of the diodes, as well switching multimeters. Always my measurement came out as 0V. So am I making some kind of mistake in measuring diodes, or are both of my multimeters/all diodes broken?

diodes multimeter

share|improve this question

asked 8 hours ago

S. RotosS. Rotos

1,03522 gold badges99 silver badges1818 bronze badges

$endgroup$

share|improve this question

asked 8 hours ago

S. RotosS. Rotos

1,03522 gold badges99 silver badges1818 bronze badges

share|improve this question

asked 8 hours ago

S. RotosS. Rotos

1,03522 gold badges99 silver badges1818 bronze badges

asked 8 hours ago

S. RotosS. Rotos

1,03522 gold badges99 silver badges1818 bronze badges

asked 8 hours ago

S. RotosS. Rotos

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5 Answers
5

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5

$begingroup$

In voltage mode, a multimeter just measures what voltage is present between its leads. What you want is diode test mode, which is usually indicated on the dial with a diode symbol. On your meter, it's the option one to the left of your voltage mode--set the dial to that and press the mode button a few times to put it in diode mode; it'll say on the LCD. In diode mode, the meter applies a known current to the diode -- you can check the meter's datasheet or instruction manual to know what current it uses, and fancier meters might even let you select a current -- and then measures the voltage across the diode.

Note that this usually won't work for LEDs, as most meters limit their diode test voltage to only one or two volts, which is too low to turn on any LEDs except maybe some red or yellow ones. But for a conventional diode like the one you show in the picture it will work fine.

share|improve this answer

answered 8 hours ago

HearthHearth

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add a comment | 

3

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Nope. You need to set your multimeter to diode test mode. One click anticlockwise, and then press the "mode" button until the LCD shows a diode symbol.

share|improve this answer

answered 8 hours ago

pericynthionpericynthion

4,7021010 silver badges2929 bronze badges

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add a comment | 

3

$begingroup$

The guys in forensics had a difficult job enhancing the dodgy photos but the problem is clear.

1. The meter is set to measure DC.


2. Volts.


3. (Barely visible in this rendering) the range selected is 'V'.


4. The correct switch setting.

Since you selected DC V and a diode doesn't generate any voltage the reading is zero. This is correct.

share|improve this answer

answered 5 hours ago

TransistorTransistor

95k88 gold badges9595 silver badges207207 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  wait, back up... there... zoom in and enhance.... Seriously though, good job on the photo!
  $endgroup$
  – mkeith
  3 hours ago
  

  
  
  
  

add a comment | 

0

$begingroup$

Perhaps you are being misled by the fact that circuit simulators model a diode as a voltage source in series with a resistor. That is a fiction that is required to make the circuit simulate correctly.

A Real diode does not produce a voltage across itself, but will produce a voltage drop when you pass current through it in the forward direction.

share|improve this answer

answered 4 hours ago

Peter BennettPeter Bennett

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-2

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If diodes generated a voltage then batteries would not be needed anymore.

share|improve this answer

answered 3 hours ago

AudioguruAudioguru

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5

$begingroup$

In voltage mode, a multimeter just measures what voltage is present between its leads. What you want is diode test mode, which is usually indicated on the dial with a diode symbol. On your meter, it's the option one to the left of your voltage mode--set the dial to that and press the mode button a few times to put it in diode mode; it'll say on the LCD. In diode mode, the meter applies a known current to the diode -- you can check the meter's datasheet or instruction manual to know what current it uses, and fancier meters might even let you select a current -- and then measures the voltage across the diode.

Note that this usually won't work for LEDs, as most meters limit their diode test voltage to only one or two volts, which is too low to turn on any LEDs except maybe some red or yellow ones. But for a conventional diode like the one you show in the picture it will work fine.

share|improve this answer

answered 8 hours ago

HearthHearth

6,81511 gold badge1616 silver badges5050 bronze badges

$endgroup$

add a comment | 

5

$begingroup$

In voltage mode, a multimeter just measures what voltage is present between its leads. What you want is diode test mode, which is usually indicated on the dial with a diode symbol. On your meter, it's the option one to the left of your voltage mode--set the dial to that and press the mode button a few times to put it in diode mode; it'll say on the LCD. In diode mode, the meter applies a known current to the diode -- you can check the meter's datasheet or instruction manual to know what current it uses, and fancier meters might even let you select a current -- and then measures the voltage across the diode.

Note that this usually won't work for LEDs, as most meters limit their diode test voltage to only one or two volts, which is too low to turn on any LEDs except maybe some red or yellow ones. But for a conventional diode like the one you show in the picture it will work fine.

share|improve this answer

answered 8 hours ago

HearthHearth

6,81511 gold badge1616 silver badges5050 bronze badges

$endgroup$

add a comment | 

$begingroup$

In voltage mode, a multimeter just measures what voltage is present between its leads. What you want is diode test mode, which is usually indicated on the dial with a diode symbol. On your meter, it's the option one to the left of your voltage mode--set the dial to that and press the mode button a few times to put it in diode mode; it'll say on the LCD. In diode mode, the meter applies a known current to the diode -- you can check the meter's datasheet or instruction manual to know what current it uses, and fancier meters might even let you select a current -- and then measures the voltage across the diode.

Note that this usually won't work for LEDs, as most meters limit their diode test voltage to only one or two volts, which is too low to turn on any LEDs except maybe some red or yellow ones. But for a conventional diode like the one you show in the picture it will work fine.

share|improve this answer

answered 8 hours ago

HearthHearth

6,81511 gold badge1616 silver badges5050 bronze badges

$endgroup$

share|improve this answer

answered 8 hours ago

HearthHearth

6,81511 gold badge1616 silver badges5050 bronze badges

answered 8 hours ago

HearthHearth

6,81511 gold badge1616 silver badges5050 bronze badges

answered 8 hours ago

HearthHearth

6,81511 gold badge1616 silver badges5050 bronze badges

3

$begingroup$

Nope. You need to set your multimeter to diode test mode. One click anticlockwise, and then press the "mode" button until the LCD shows a diode symbol.

share|improve this answer

answered 8 hours ago

pericynthionpericynthion

4,7021010 silver badges2929 bronze badges

$endgroup$

add a comment | 

3

$begingroup$

Nope. You need to set your multimeter to diode test mode. One click anticlockwise, and then press the "mode" button until the LCD shows a diode symbol.

share|improve this answer

answered 8 hours ago

pericynthionpericynthion

4,7021010 silver badges2929 bronze badges

$endgroup$

add a comment | 

$begingroup$

Nope. You need to set your multimeter to diode test mode. One click anticlockwise, and then press the "mode" button until the LCD shows a diode symbol.

share|improve this answer

answered 8 hours ago

pericynthionpericynthion

4,7021010 silver badges2929 bronze badges

$endgroup$

share|improve this answer

answered 8 hours ago

pericynthionpericynthion

4,7021010 silver badges2929 bronze badges

answered 8 hours ago

pericynthionpericynthion

4,7021010 silver badges2929 bronze badges

answered 8 hours ago

pericynthionpericynthion

4,7021010 silver badges2929 bronze badges

3

$begingroup$

The guys in forensics had a difficult job enhancing the dodgy photos but the problem is clear.

1. The meter is set to measure DC.


2. Volts.


3. (Barely visible in this rendering) the range selected is 'V'.


4. The correct switch setting.

Since you selected DC V and a diode doesn't generate any voltage the reading is zero. This is correct.

share|improve this answer

answered 5 hours ago

TransistorTransistor

95k88 gold badges9595 silver badges207207 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  wait, back up... there... zoom in and enhance.... Seriously though, good job on the photo!
  $endgroup$
  – mkeith
  3 hours ago
  

  
  
  
  

add a comment | 

3

$begingroup$

The guys in forensics had a difficult job enhancing the dodgy photos but the problem is clear.

1. The meter is set to measure DC.


2. Volts.


3. (Barely visible in this rendering) the range selected is 'V'.


4. The correct switch setting.

Since you selected DC V and a diode doesn't generate any voltage the reading is zero. This is correct.

share|improve this answer

answered 5 hours ago

TransistorTransistor

95k88 gold badges9595 silver badges207207 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  wait, back up... there... zoom in and enhance.... Seriously though, good job on the photo!
  $endgroup$
  – mkeith
  3 hours ago
  

  
  
  
  

add a comment | 

$begingroup$

The guys in forensics had a difficult job enhancing the dodgy photos but the problem is clear.

1. The meter is set to measure DC.


2. Volts.


3. (Barely visible in this rendering) the range selected is 'V'.


4. The correct switch setting.

Since you selected DC V and a diode doesn't generate any voltage the reading is zero. This is correct.

share|improve this answer

answered 5 hours ago

TransistorTransistor

95k88 gold badges9595 silver badges207207 bronze badges

$endgroup$

share|improve this answer

answered 5 hours ago

TransistorTransistor

95k88 gold badges9595 silver badges207207 bronze badges

answered 5 hours ago

TransistorTransistor

95k88 gold badges9595 silver badges207207 bronze badges

answered 5 hours ago

TransistorTransistor

95k88 gold badges9595 silver badges207207 bronze badges

0

$begingroup$

Perhaps you are being misled by the fact that circuit simulators model a diode as a voltage source in series with a resistor. That is a fiction that is required to make the circuit simulate correctly.

A Real diode does not produce a voltage across itself, but will produce a voltage drop when you pass current through it in the forward direction.

share|improve this answer

answered 4 hours ago

Peter BennettPeter Bennett

38.9k11 gold badge3131 silver badges7171 bronze badges

$endgroup$

add a comment | 

0

$begingroup$

Perhaps you are being misled by the fact that circuit simulators model a diode as a voltage source in series with a resistor. That is a fiction that is required to make the circuit simulate correctly.

A Real diode does not produce a voltage across itself, but will produce a voltage drop when you pass current through it in the forward direction.

share|improve this answer

answered 4 hours ago

Peter BennettPeter Bennett

38.9k11 gold badge3131 silver badges7171 bronze badges

$endgroup$

add a comment | 

$begingroup$

Perhaps you are being misled by the fact that circuit simulators model a diode as a voltage source in series with a resistor. That is a fiction that is required to make the circuit simulate correctly.

A Real diode does not produce a voltage across itself, but will produce a voltage drop when you pass current through it in the forward direction.

share|improve this answer

answered 4 hours ago

Peter BennettPeter Bennett

38.9k11 gold badge3131 silver badges7171 bronze badges

$endgroup$

share|improve this answer

answered 4 hours ago

Peter BennettPeter Bennett

38.9k11 gold badge3131 silver badges7171 bronze badges

answered 4 hours ago

Peter BennettPeter Bennett

38.9k11 gold badge3131 silver badges7171 bronze badges

answered 4 hours ago

Peter BennettPeter Bennett

38.9k11 gold badge3131 silver badges7171 bronze badges

-2

$begingroup$

If diodes generated a voltage then batteries would not be needed anymore.

share|improve this answer

answered 3 hours ago

AudioguruAudioguru

61311 silver badge44 bronze badges

$endgroup$

add a comment | 

-2

$begingroup$

If diodes generated a voltage then batteries would not be needed anymore.

share|improve this answer

answered 3 hours ago

AudioguruAudioguru

61311 silver badge44 bronze badges

$endgroup$

add a comment | 

$begingroup$

If diodes generated a voltage then batteries would not be needed anymore.

share|improve this answer

answered 3 hours ago

AudioguruAudioguru

61311 silver badge44 bronze badges

$endgroup$

share|improve this answer

answered 3 hours ago

AudioguruAudioguru

61311 silver badge44 bronze badges

answered 3 hours ago

AudioguruAudioguru

61311 silver badge44 bronze badges

answered 3 hours ago

AudioguruAudioguru

61311 silver badge44 bronze badges