LCR meter and diode capacitance measurment at 1MHz

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#21
Not all components specifications documents are made by the same quality.
In one of them found this text. Measured at 1.0MHz and applied reverse voltage of 4.0V DC

Therefor my portable LCR does not have this capability, and in conclusion my prior made measurements, them have just an educational value.

When you seek accuracy in a measurement your measuring device this must be fully compatible with the one that the electronic components manufacturer have use in his own measurements.
 
#22
JMFahey said:
What's wrong with putting a known value adjustable inductor in series or parallel with the unknown capacitor, feed said tank 1MHz at a suitable (low) level and adjust the inductor until you get a defined dip or peak?

You might also use a grid dip meter.
Click to expand...

In my application the diodes was supposed to act as additional EMF filter, by using two diodes in series and them connected to earth.
My project was about making an LM35 temperature sensor this to operate with my oscilloscope.
I did all ready an RC filter so this to fight back capacitive load of the coaxial cable that I am using so to connect it to my Oscilloscope.

Here is my project - perfectly working. 😉
Oscilloscope and temperature measurement by using LM35 sensor
 
#23
Kiriakos
You should be able to power your diode in reverse bias through a large resistor, then apply your LCR meter through a capacitor to block DC. If this capacitor is (lots bigger) than the diode capacitance then the diode capacitance should be read on the meter. With 0.5V signal I agree 4V reverse bias should give a reasonably consistent reading.
 
#24
Kiriakos said:
You need to go back to kindergarten because any measurement far and away from the specified by the manufacturer it self as product test frequency, all numbers them are invalid.

As more close to the truth I do consider all measurements from 1KHz and above.
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I know English is not your first language, but it is mine! I mostly have no idea what you are talking about in your posts. 😱
 
#25
john_ellis said:
Kiriakos
You should be able to power your diode in reverse bias through a large resistor, then apply your LCR meter through a capacitor to block DC. If this capacitor is (lots bigger) than the diode capacitance then the diode capacitance should be read on the meter. With 0.5V signal I agree 4V reverse bias should give a reasonably consistent reading.
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John thanks for the tip but in such diodes their specification this is close to 4~5 pF at 1MHz.

For now and just of curiosity I would like some one with a bench-top 1 MHz LCR, him to measure one 1N5819 with 4V reverse voltage but at 100KHz instead of 1 MHz.
Just for me to see how much influence causes to the measurement the addition of the reverse bias voltage.
 
#27
Kiriakos said:
I would like some one with a bench-top 1 MHz LCR, him to measure one 1N5819 with 4V reverse voltage but at 100KHz instead of 1 MHz.
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There must be many many people on diyAudio who are grateful for a response made by Kiriakos, a post reply containing kind assistance and insightful analysis. Surely there is at least one person who would be glad to thank Kiriakos for helping him personally, and who also owns a bench-top 1MHz LCR meter ?
 
#28
I don't have access to an LCR meter. If a signal generator is available it's possible to use a series resistance and an Oscilloscope to measure the impedance. I have just used the technique to measure the high frequency impedance of an 8 ohm load.
 

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#33
Originally Posted by Kiriakos View Post
No one own such a magic box in this large community ?
Good to know so to never start again an topic for big boys in a DIY forum.
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Well, there are a couple "big boys" Forums out there, namely Physics ones, but I'm afraid you won't be able to post your questions there, mainly because you won't be able to pass the "big boys" 5 Physics problems quiz you must solve before even being admitted.

Plus sending a short resume stating your Qualifications, although including some links for a few contributions to peer reviewed scientific magazines may help in making the process smoother.
Just sayin'
 
#36
Morgan Jones in Linear Audio - Volume 5 measures and discusses diode capacitance. For measurements at frequencies above 200 kHz a function generator and oscilloscope was used. Figue 8 shows the test set-up and also states 'the cost of an analyser that measures >200 kHz is prohibitive'.
 
#37
PChi said:
Morgan Jones in Linear Audio - Volume 5 measures and discusses diode capacitance. For measurements at frequencies above 200 kHz a function generator and oscilloscope was used. Figue 8 shows the test set-up and also states 'the cost of an analyser that measures >200 kHz is prohibitive'.
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I am afraid Morgan Jones is incorrect...there are many designs of "voltage network analyzers" which can be built for under $100. It's not Agilent/Keysight/HP but close for our work -- using off the shelf components.
 
#39
Kiriakos said:
This is where you are wrong, slow diodes them are made to serve at 50-60Hz , them is not our topic.

The all conversation is about FAST switching diodes, them they get tested at 1MHz.

And now lets talk with facts, diode 1N5819 this tested at several frequencies.
100Hz this measured 108.56 uF
120Hz ...... 118.73 uF
1K ..... 10.570 uF
10K ..... 1102 nF ( about 1uF + )
100KHz ... 105.55 nF ( 1/10 of 1uF)

Now is it possible someone to measure this specific diode at 1 MHz?
Click to expand...
did you check the voltage was not changed for each of the test frequencies?
 
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