EEVblog 1473 - How Your LCR Meter Works - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: May 19, 2022, 02:08:52 pm
content: How an LCR meter works.Part 2:

author: mawyatt
author_rank: Super Contributor
timestamp: May 19, 2022, 02:56:56 pm
content: Excellent video as usual DaveJust 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.Best,

author: HighVoltage
author_rank: Super Contributor
timestamp: May 19, 2022, 04:23:35 pm
content: Nice video,The Philips / Fluke LCR meters came a a few good charts and they showed exactly what you explained.

author: EEVblog
author_rank: Unknown
timestamp: May 20, 2022, 12:40:54 am
content: Quote from: mawyatt on May 19, 2022, 02:56:56 pmYep, correct.

author: jknightandkarr
author_rank: Contributor
timestamp: May 20, 2022, 12:51:40 am
content: 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

author: EEVblog
author_rank: Unknown
timestamp: May 20, 2022, 02:04:41 am
content: Quote from: jknightandkarr on May 20, 2022, 12:51:40 amhttps://www.ak-modul-bus.de/cgi-bin/iboshop.cgi?showdsearchrlc%3A11111100%210%2C746296692357891%2CRLC-Box2

author: thm_w
author_rank: Super Contributor
timestamp: May 20, 2022, 09:15:53 pm
content: 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.

author: EEVblog
author_rank: Unknown
timestamp: May 21, 2022, 03:53:57 am
content: Quote from: thm_w on May 20, 2022, 09:15:53 pmThey have varying DC offsets that I measured, and measurements may only be taken at 0 and 90deg, so that's effectively one polarity.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 21, 2022, 10:28:53 am
content: Quote from: thm_w on May 20, 2022, 09:15:53 pmI 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).

author: harrimansat
author_rank: Regular Contributor
timestamp: May 26, 2022, 07:39:03 pm
content: 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

author: HighVoltage
author_rank: Super Contributor
timestamp: May 26, 2022, 09:18:34 pm
content: Quote from: harrimansat on May 26, 2022, 07:39:03 pmIs that a live update on the PC from the Tektronix THS?

author: EEVblog
author_rank: Unknown
timestamp: May 27, 2022, 05:57:51 am
content: Quote from: harrimansat on May 26, 2022, 07:39:03 pmOld school

author: harrimansat
author_rank: Regular Contributor
timestamp: May 27, 2022, 04:59:37 pm
content: Quote from: HighVoltage on May 26, 2022, 09:18:34 pmYes, 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

author: HighVoltage
author_rank: Super Contributor
timestamp: May 28, 2022, 08:40:29 am
content: Quote from: harrimansat on May 27, 2022, 04:59:37 pmInteresting!Yes, please attach it, just for fun.Thanks

author: harrimansat
author_rank: Regular Contributor
timestamp: May 28, 2022, 12:45:40 pm
content: Quote from: HighVoltage on May 28, 2022, 08:40:29 am

author: harrimansat
author_rank: Regular Contributor
timestamp: May 28, 2022, 12:54:46 pm
content: 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.