LCR Meter Vs. Curve Tracing (The Octopus Circuits) - Page 1
Forum section: electronics / beginners

author: ShreveCC
author_rank: Contributor
timestamp: March 21, 2015, 07:35:25 pm
content: I have a curious rookie\young player\seasoned electronic tech topic:The LCR meter Vs Curve Tracing with your Oscilloscope? The benefits and weakness to each other. When would a tech\engineer choose one method of testing over the other? Is an LCR meter really worth the expense over just curve tracing component?

author: Paul Moir
author_rank: Frequent Contributor
timestamp: March 21, 2015, 07:54:15 pm
content: I think I see where you're coming from. Octopus like this?http://www.qsl.net/kd7rem/octopus.htmlLCR meters are really for measuring rather than testing (though they are quite handy for checking electrolytic capacitor's ESR). So something like the Octopus you mention can be helpful for quickly checking if components are working or not working, while an LCR meter can tell you the exact inductance of that coil you just wound.LCR meters often can read much lower or higher values that you can with something like an Octopus. For example the DE-5000 has a ohms resolution of .001 ohm and can read up to 200 Mohm. Down to tens of femto farads and nanohenrys.LCR meters are usually fairly delicate due to their very sensitive inputs. They tend to be expensive like you said but the DE-5000 has kind of redefined the range.

author: ShreveCC
author_rank: Contributor
timestamp: March 21, 2015, 09:02:16 pm
content: Yes, you found one of the hundreds of "curve trace" circuits or methods that I am curious about. I was actually going to post this topic earlier, before I made an LCR purchase (the wife is going to beat me for another expensive "tech toy"). LCR meters can make your head spin on the quality to price ratio, but alas I choose an Applent AT825 for the sorting and bad ESR cap hunts... thank you for responding.Another "curve test", and the one that I like to use for ESR, is with my frequency generator and my scope. It works great for ESR checks, haven't test driven for other uses, but can be done in-circuit... to a point...as you may already know the cautions.I set my frequency generator for a square wave at 1~100Khz 50mV p-p and at 50 Ohm impedance. I than connect a BNC "T" connector to the generator. After the connection to the generator is done, I run a BNC cable on one end of the "T" to my scope and the other end of the "T" to a pair of BNC SMD Tweezers or alligators. Tweeze or clip a suspicious capacitor- ... if I don't see the square wave in any form other than a peak to peak straight line on the scope... it is a "good enough" cap in my book.

author: dannyf
author_rank: Super Contributor
timestamp: March 21, 2015, 09:17:36 pm
content: QuoteHappy wife, happy life. No amount of "tech toy" is worthy of pissing her off.QuoteFor that, many simple plans will work. I built one around a dual opamp like NE5532. Check it out - it is more than sufficient to do what you are trying to do.

author: codeboy2k
author_rank: Super Contributor
timestamp: March 21, 2015, 09:50:36 pm
content: Quote from: dannyf on March 21, 2015, 09:17:36 pmnew wife then?

author: Seekonk
author_rank: Super Contributor
timestamp: March 21, 2015, 10:41:38 pm
content: I had that HEATH scope 50 years ago when I was a kid, it was old then. My camp is solar powered with 1500W of panels. My wife is in a rewards program at the wine store near the camp. In the last four years she has spent more on wine than my entire solar power system cost. At least I didn't piss my money away.

author: Fraser
author_rank: Super Contributor
timestamp: March 21, 2015, 11:12:28 pm
content: IMHO the 'Octopus' is a very useful tool for looking at semiconductor junctions, but less so for looking at whether a capacitor is good or bad. I use the Hameg oscilloscope Component Test function and also Huntron Tracker's. These are just a fancy (refined) Octopus tester. They are also good for looking at potentiometers to see whether the track is noisy !For capacitor, resistor and Inductor testing I use an LCR meter and an ESR meter. My Mastech MS5308 and DEREE DE-5000 ESR meters are very useful bits of kit that I can recommend. They can tell you a lot more about the component than a simple Octopus tester. It is possible to build more sophisticated I-V component analyzers but I would still want an ESR meter these days as a fast and effective means of MEASURING the actual ESR of a suspect capacitor.There are very affordable ESR and LCR meters on e*ay that will serve well in many situations so you do not need to invest a lot of money in one if your needs are not too great. I bought some nicely cased ESR meters from China and they work very well but have less facilities than the more expensive models.http://www.ebay.co.uk/itm/DER-EE-DE-5000-High-Accuracy-Handheld-LCR-Meter-from-Japan-/111620276339?pt=LH_DefaultDomain_0&hash=item19fd164073The DEREE DE5000 offering from Japan is hard to beat in terms of bang for your buck though:http://www.ebay.co.uk/itm/DER-EE-DE-5000-High-Accuracy-Handheld-LCR-Meter-from-Japan-/111620276339?pt=LH_DefaultDomain_0&hash=item19fd164073Just my 2 CentsAurora

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 21, 2015, 11:51:15 pm
content: Quote from: codeboy2k on March 21, 2015, 09:50:36 pmyou make it sounded easy as if a wife is a "tech toy"Quote from: Paul Moir on March 21, 2015, 07:54:15 pmin order to test or check... we need to measure first isnt it? for purely measurement purpose, usually one is to head on to concern about precision isnt it?

author: GreyWoolfe
author_rank: Unknown
timestamp: March 22, 2015, 12:22:47 am
content: I built the W2AEW octopus:It works well with my Tektronix 2235. Also have Der EE DE-5000.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: March 22, 2015, 01:54:55 am
content: Quote from: Mechatrommer on March 21, 2015, 11:51:15 pmI think we just have a communication problem here, and that we are in agreement: Yes you're right, when testing or checking is first thing you do is to measure. I meant to say the purpose of LCR meters is primarily for precise quantitative measurements. My argument is that when testing or checking you don't care about + or - 10% or more, which is easily seen on an oscilloscope screen.If we are in agreement, the misunderstanding was due to a poor choice of words on my part.

author: Shock
author_rank: Super Contributor
timestamp: March 22, 2015, 04:47:05 am
content: An octopus generally shows you VI curve at a certain frequency and current. In order to confirm some degree of accuracy you need to be familiar with the waveform, have the measurements on hand or do a comparative check with waveform of a known good component. Requires an oscilloscope.LCR meters record the components operating characteristics or other relationships that should warn if the component is likely drifting out of spec, or used when matching and sorting is required. They are used by manufacturers themselves which is useful for tolerance checks, and can be obtained cheaply, as low as $10 to $100, while the more expensive bench models have a wider frequency, range of operation and accuracy.An LCR meter along with a transistor/semiconductor tester and multimeter should cover a lot of situations. I think an LCR meter is more useful than an octopus, and if you have other multi-function meters that can take capacitance, inductance and ESR measurements you may have most of the functionality of an LCR meter covered already.

author: glicos
author_rank: Regular Contributor
timestamp: March 22, 2015, 05:09:09 am
content: Quote from: Shock on March 22, 2015, 04:47:05 amAGREE.Nowadays, you can buy cheap ESR+LCR+Semiconductor tester from china if used for repair and troubleshooting task only. Though not recommended for serious work, but useful nontheless. Sample here with zener diode check option for around $44http://www.aliexpress.com/item/Transistor-Tester-Capacitor-ESR-Inductance-Resistor-Meter-Mosfet-Diode-Battery/1939673764.html

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: March 22, 2015, 06:14:40 am
content: Look to this thread.https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg195093/#msg195093you will find a lot of discussion for less than 20$ ESR meter. I have one with a atmega328 that I put on a zif socketso it is very convenient to program to the latest firmware.This is my most useful tool after the DMM for repairing stuff.This tool is amazing as it can check resistor, capacitors, ESR, but also transistors, diodes, triacs, ...Often it can be done on board.

author: dannyf
author_rank: Super Contributor
timestamp: March 22, 2015, 11:22:51 am
content: RE: octopus.It can be used to measure (small) capacitance and (large) inductance, without a scope but just a multimeter.Essentially, put the capacitor in serial with the multimeter (on Vac setting) and apply an ac signal (from a transformer or if safety is of no concern, the ac mains directly). The reading on the multimeter will go up with the capacitance almost linearly, up to 100pf (error at that point is just over 5%).

author: ShreveCC
author_rank: Contributor
timestamp: March 22, 2015, 07:12:42 pm
content: Quote from: dannyf on March 21, 2015, 09:17:36 pmIt's an expression on the wife part- she is happy with me (as long I don't explain the "toys" to her), and I am happy with her:My interests\hobbies go into areas over her head, except when dollars are mentioned for coming "in" or dollars coming "out" are considered. However, her eyes are always smiling when the "tech-gizmos" make us money, so she only whines when I try to explain the "tech-gizmos" to her. I gave up on "serious" explanations of "gizmos" to her awhile ago.

author: ShreveCC
author_rank: Contributor
timestamp: March 22, 2015, 07:40:16 pm
content: Quote from: GreyWoolfe on March 22, 2015, 12:22:47 amHello GreyWoolfe, I know your design, I have learned a lot from your videos and Mr. Jones youtube videos.; The video you linked is actually how this topic started. I added your curve tracing method to my electronic knowledge bag, thank-you very much.I believe your a ham radio guy, so is my father - KC8LLN in Michigan.

author: ShreveCC
author_rank: Contributor
timestamp: March 22, 2015, 08:26:50 pm
content: Quote from: Aurora on March 21, 2015, 11:12:28 pmThank-you Aurora... your right on japan, I picked this as my second choice, but I commited to the purchase of the Applent AT825, I liked the test review/price on this device.

author: GreyWoolfe
author_rank: Unknown
timestamp: March 22, 2015, 10:13:37 pm
content: Quote from: ShreveCC on March 22, 2015, 07:40:16 pmShreveCC, I am not the one who designed it, Alan, W2AEW is the one who designed, I just built it for myself. I am also a ham radio guy, NW0LF is my callsign.Tom, NW0LF