Electronics > Beginners
Testing Silicon Rectifier Diode
Wimberleytech:
--- Quote from: magic on November 06, 2019, 07:10:17 am ---A DMM will measure 1.1V just fine, but you need to use volts mode and apply the test current externally from other source :)
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Of course...I was referring to the diode test mode common on modern DMMs. I checked my Fluke 87V...it tests a blue led just fine. Presents an open circuit voltage around 7 volts
Kirill V.:
--- Quote from: mr.fabe on November 05, 2019, 06:24:14 pm ---Besides a resistance check for open/close
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I'm sorry, but this is the first time I've heard of such parameters. Maybe I'm behind the times?
Direct voltage drop and breakdown voltage are usually measured...
Measuring the reverse breakdown voltage is best done with some kind of current source and voltmeter parallel to the diode. In this case, this is a non-trivial task, but the current source can be replaced with a high voltage source and a resistor to limit the value of current through the test diode.
mr.fabe:
--- Quote from: Kirill V. on November 06, 2019, 05:46:29 pm ---
--- Quote from: mr.fabe on November 05, 2019, 06:24:14 pm ---Besides a resistance check for open/close
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I'm sorry, but this is the first time I've heard of such parameters. Maybe I'm behind the times?
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My mistake. I stated "open/close" incorrectly and confused the issue. Resistance check as a test that you can perform with normal diodes. The point is that the normal DMM diode tests failed with HV diodes. I am aware of testing at rated voltage but sought an alternative method to test at a lower voltage to determine if a HV diode is operating properly.
Kirill V.:
The matter is that semiconductors and ohmic contacts have resistance and too create voltage drop which is added to 0,7 volts of voltage drop at pn junction. As far as I know, HV diodes has more high resistance of semiconductor that another diodes. Therefore, the voltage drop on the diode you are interested in is 1.1 volts at a current of 1 amp, but the voltage drop at pn junction is 0.7 volts approximately, and everything else is ohmic losses. At low direct currents this voltage will not exceed 0.7 volts and can be measured with a DMM.
There are diodes that can not afford a DMM
This is HV diode array. Now I uses amperemeter and voltmeter for testing. Direct current 8 mA, drop voltage 18,6 V
These are diodes that cannot be measured with a conventional DMM. In datasheet says that maximum drop voltage equal 25 V at 10 mA current, therefore they passed the test:)
mr.fabe:
Thank you all for your input!
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