Author Topic: EEVblog 1473 - How Your LCR Meter Works  (Read 4867 times)

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Offline EEVblogTopic starter

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EEVblog 1473 - How Your LCR Meter Works
« on: May 19, 2022, 02:08:52 pm »
How an LCR meter works.



Part 2:
« Last Edit: May 19, 2022, 02:13:33 pm by EEVblog »
 

Offline mawyatt

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Re: EEVblog 1473 - How Your LCR Meter Works
« Reply #1 on: May 19, 2022, 02:56:56 pm »
Excellent video as usual Dave :-+

Just a small note, on the graph of jX vs. R. The vector is indicated as Xs (at least seems so on the graph), this vector should be the DUT impedance or Rs + jXs and when projected to the jX axis (Vert) is Xs and when projected to R axis (Horz) is Rs.

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Offline HighVoltage

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Re: EEVblog 1473 - How Your LCR Meter Works
« Reply #2 on: May 19, 2022, 04:23:35 pm »
Nice video,

The Philips / Fluke LCR meters came a a few good charts and they showed exactly what you explained.
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Offline EEVblogTopic starter

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Re: EEVblog 1473 - How Your LCR Meter Works
« Reply #3 on: May 20, 2022, 12:40:54 am »
Excellent video as usual Dave :-+

Just a small note, on the graph of jX vs. R. The vector is indicated as Xs (at least seems so on the graph), this vector should be the DUT impedance or Rs + jXs and when projected to the jX axis (Vert) is Xs and when projected to R axis (Horz) is Rs.

Yep, correct.
 

Offline jknightandkarr

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Re: EEVblog 1473 - How Your LCR Meter Works
« Reply #4 on: May 20, 2022, 12:51:40 am »
Since it was in your video, and would help me learn this subject better.  Where did your open source capacitor substitution box come from??

Joe
 

Offline EEVblogTopic starter

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Re: EEVblog 1473 - How Your LCR Meter Works
« Reply #5 on: May 20, 2022, 02:04:41 am »
Since it was in your video, and would help me learn this subject better.  Where did your open source capacitor substitution box come from??

https://www.ak-modul-bus.de/cgi-bin/iboshop.cgi?showdsearchrlc%3A11111100%210%2C746296692357891%2CRLC-Box2
 

Online thm_w

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Re: EEVblog 1473 - How Your LCR Meter Works
« Reply #6 on: May 20, 2022, 09:15:53 pm »
So how does flipping the meter do anything if the output signal is AC with no offset?
I guess that implies the LCR meter is only sampling on the positive half of the sine wave, for cost/simplicity reasons.

Could potentially have a more advanced LCR/component tester that samples both halves and tells you what it sees in either polarity.
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Offline EEVblogTopic starter

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Re: EEVblog 1473 - How Your LCR Meter Works
« Reply #7 on: May 21, 2022, 03:53:57 am »
So how does flipping the meter do anything if the output signal is AC with no offset?
I guess that implies the LCR meter is only sampling on the positive half of the sine wave, for cost/simplicity reasons.

Could potentially have a more advanced LCR/component tester that samples both halves and tells you what it sees in either polarity.

They have varying DC offsets that I measured, and measurements may only be taken at 0 and 90deg, so that's effectively one polarity.
 

Offline Kleinstein

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Re: EEVblog 1473 - How Your LCR Meter Works
« Reply #8 on: May 21, 2022, 10:28:53 am »
So how does flipping the meter do anything if the output signal is AC with no offset?
I guess that implies the LCR meter is only sampling on the positive half of the sine wave, for cost/simplicity reasons.

Could potentially have a more advanced LCR/component tester that samples both halves and tells you what it sees in either polarity.

I would not expect them to sample only one polarity half the wave: it does not same much on the cost side and makes it sensitive to DC offsets. So it is more like save costs by sampling the whole wave and this way don't worry about DC offsets and save there.

It depends on the meter if they have an DC offset or not. Also the amplitude of the test signal can vary. So some meters can be more suiteable for in circuit test than others.

Changing the leads can still effect the effect of parasitic capacitance. Chances are one of the leads is more sensitive to parasitic capacitance than the other. This can especially make a difference when measuring in circuit or with small capacitors (e.g. < 1 nF).
 

Offline harrimansat

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Re: EEVblog 1473 - How Your LCR Meter Works
« Reply #9 on: May 26, 2022, 07:39:03 pm »
To measure capacitors in board I use a XY oscilloscope with a funtion generator with DC offset to meassure only de capacitive region. You can select a small vpp and a large dc offset to avoid diode



 
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Offline HighVoltage

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Re: EEVblog 1473 - How Your LCR Meter Works
« Reply #10 on: May 26, 2022, 09:18:34 pm »
To measure capacitors in board I use a XY oscilloscope with a funtion generator with DC offset to meassure only de capacitive region. You can select a small vpp and a large dc offset to avoid diode


Is that a live update on the PC from the Tektronix THS?
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Offline EEVblogTopic starter

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Re: EEVblog 1473 - How Your LCR Meter Works
« Reply #11 on: May 27, 2022, 05:57:51 am »
To measure capacitors in board I use a XY oscilloscope with a funtion generator with DC offset to meassure only de capacitive region. You can select a small vpp and a large dc offset to avoid diode

Old school  :-+
 

Offline harrimansat

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Re: EEVblog 1473 - How Your LCR Meter Works
« Reply #12 on: May 27, 2022, 04:59:37 pm »
To measure capacitors in board I use a XY oscilloscope with a funtion generator with DC offset to meassure only de capacitive region. You can select a small vpp and a large dc offset to avoid diode


Is that a live update on the PC from the Tektronix THS?

Yes, is a live update at 38400bps, the "trick" is read only 128 points per sweep. I can attach de VI if you want to try it
 

Offline HighVoltage

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Re: EEVblog 1473 - How Your LCR Meter Works
« Reply #13 on: May 28, 2022, 08:40:29 am »
To measure capacitors in board I use a XY oscilloscope with a funtion generator with DC offset to meassure only de capacitive region. You can select a small vpp and a large dc offset to avoid diode


Is that a live update on the PC from the Tektronix THS?

Yes, is a live update at 38400bps, the "trick" is read only 128 points per sweep. I can attach de VI if you want to try it

Interesting!
Yes, please attach it, just for fun.
Thanks
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Offline harrimansat

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Re: EEVblog 1473 - How Your LCR Meter Works
« Reply #14 on: May 28, 2022, 12:45:40 pm »
To measure capacitors in board I use a XY oscilloscope with a funtion generator with DC offset to meassure only de capacitive region. You can select a small vpp and a large dc offset to avoid diode


Is that a live update on the PC from the Tektronix THS?

Yes, is a live update at 38400bps, the "trick" is read only 128 points per sweep. I can attach de VI if you want to try it

Interesting!
Yes, please attach it, just for fun.
Thanks
 
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Offline harrimansat

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Re: EEVblog 1473 - How Your LCR Meter Works
« Reply #15 on: May 28, 2022, 12:54:46 pm »
automatically says if it is a capacitor or an inductor. It works but there are things to correct. I remember that the main calculation must be done from the phase and right now it doesn't work like that. The calculation of the very resistive inductance is not correct, for example. It is because the first version was only for measuring capacitors.
 


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