Recommendation for low cost LCR meter - Page 1
Forum section: electronics / general

author: kc1980
author_rank: Regular Contributor
timestamp: May 05, 2010, 12:16:21 am
content: Can anyone recommend me an inexpensive LCR meter for hobby use? I'd prefer a hand-held over a bench unit. Thanks in advance....or, maybe I should make one???

author: Unknown
author_rank: Unknown
timestamp: May 05, 2010, 05:03:20 am
content: I believe the leader in the hobbyist market is theAADE L/C meter. It doesn't do the R part, only L and C. It's available as a kit or pre-assembled. The build quality is not on the level of a professional case, but better than many hobby projects. I like the high resolution, I can accurately measure a few pF (assuming the parasitic capacitance in my test setup is constant). It's much better than the capacitance range of my Fluke DMM's in that respect. It won't do large capacitors (like most electrolytic caps), but I don't often find a need to measure them anyway. For testing for broken ones, an ESR meter is much more useful. >1uF capacitors are rarely in places like filters were accurate capacitance is important.

author: Polossatik
author_rank: Frequent Contributor
timestamp: May 05, 2010, 08:27:44 am
content: Quote from: kc1980 on May 05, 2010, 12:16:21 amI don't have this, but thehttp://electronics-diy.com/lc_meter.phplooks pretty neat.I found no download of the pic source code, but they sell kits.

author: kc1980
author_rank: Regular Contributor
timestamp: May 06, 2010, 09:23:07 pm
content: I have somewhat of a theoretical question regarding impedance. Are the resistance, capacitance and inductance of real-world, non-ideal discrete resistors, capacitors and inductors (respectively) frequency-dependent? I understand that reactance is proportional to frequency, but what about the actual value of L or C, which is ideally constant. I'm assuming that it does change with frequency, but is the effect negligible?This leads to my next question: What frequencies are typically used to measure R (i.e. ESR), L, C?Thanks!Ken

author: mkissin
author_rank: Regular Contributor
timestamp: May 06, 2010, 10:38:02 pm
content: Yes, they can be heavily dependent on frequency, but that's a sweeping generalisation that will be of no real help to you.Take the easiest case: resistance.The resistance of a small, straight piece of single-stranded copper wire at DC at 25° is really simple to calculate. As soon as you put AC into it, that value is no longer valid. Skin effect (which is itself a complicated magnetic thing) dictates that the current will tend to flow preferentially at the surface of the conductor, meaning that less current will flow in the centre of the conductor. Take that a wee bit further and you can get to a high enough frequency (which often isn't that high, a few kHz) where there will be no current flowing in the centre of the conductor. Which means you might as well use a copper pipe rather than a solid piece of wire. The AC resistance will have increased due to the fact that you now have less area of copper which is actually being used to conduct the current.Capacitance and inductance also vary wildly with frequency, but are much more complex as you now have to take into account the properties of the dielectric material of the capacitor, or any core material used in the inductor. That's in addition to the geometry of the component itself. Often your choice of package will have a large effect on how well the component performs over a frequency range. Surface mount capcitor packages will naturally have lower values of parasitic inductance than through-hole simply due to the lack of long leads.In extreme cases, the inductor you carefully wound can end up looking like a resistor (at one very precise frequency), or even a capacitor!Typical test frequencies offered by cheaper test equipment are 50/60Hz, 1kHz, 10kHz, and sometimes 100kHz. Ideally, you want to measure the properties of your component at the frequency it will be operating at.

author: EEVblog
author_rank: Unknown
timestamp: May 06, 2010, 11:54:29 pm
content: BTW, I should be reviewing the Extech LCR meter soon.http://www.extech.com/instruments/product.asp?catid=56&prodid=349Dave.

author: kc1980
author_rank: Regular Contributor
timestamp: May 07, 2010, 07:52:18 am
content: Cool! Thanks mkissin for the detailed reply.I've very familiar with the skin effect. We use flat-braided grounding straps to minimized voltage drops in the event that lighting strikes the airplane fuselage. And with capacitors, I guess the "dielectric constant" isn't truly a scalar constant; it is complex with respect to frequency.

author: Zad
author_rank: Super Contributor
timestamp: May 07, 2010, 07:12:08 pm
content: Analog Devices do a nifty chip that you may be interested in: AD5933: 1 MSPS, 12 Bit Impedance Converter Network Analyzerhttp://www.analog.com/en/rfif-components/direct-digital-synthesis-dds/ad5933/products/product.htmlIt would take a bit of work with an external micro, but it would be an interesting project:

author: dimlow
author_rank: Frequent Contributor
timestamp: May 07, 2010, 09:13:30 pm
content: I just ordered the ESR Micro v4, looks good, they also have the ESR micro V3.1 that is very cheep and has had good reviews. Here is a page that has links to buy and links to the designers site.http://preher-tech.com/esrmicro.aspx

author: Rhythmtech
author_rank: Regular Contributor
timestamp: July 28, 2010, 08:33:53 pm
content: I recently bought aUni-T UT603The main consideration was price - $39.68 shipped and my need was mostly based on just wanting rough values of inductors pulled from boards I salvaged. I was willing to accept lowered measurement range and resolution to be able to measure inductance.Taking into account the price:Pros:The unit is stout, feels good in the hand, works well propped on its tilting bale, and the manual is not horrible.The diode test lit up an LED at 1735 mV.I generally stay away from meters with transistor testers on them, but in this case I am kind of happy it is on my "cheapy" LCR meter, just in case I find a use for testing transistors out of circuit.I now have an LCR meter...Cons:The through-case test terminals don't seem to line up and suck the leads in well, about 50% of the time I have to take a little extra care to thread the leads in nicely.Power button is mechanical, if you leave it on you're batt will be dead.I want more resolution, accuracy, and ranges.Not Autoranging!!!!!! arggh, but given the price....I wish it said Agilent on it.

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 29, 2010, 01:06:16 pm
content: Quote from: polossatik on May 05, 2010, 08:27:44 amif just someone could explain how to feed the analog circuit ofhttp://electronics-diy.com/img/lc_meter_pic16f84a.jpginhttp://electronics-diy.com/lc_meter.php, from PIC chip i will be glad to program this. i know about the formula f = 1 / (2pi sqrt(LC)), but the explanation about "freq this and freq that" makes me boggled!and whats the reed relay?

author: ElektroQuark
author_rank: Unknown
timestamp: July 29, 2010, 01:25:38 pm
content: Reed relay is a relaybut it needs a few milliamps to work, so it can be driven directly by a PIC pin.

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 29, 2010, 01:54:17 pm
content: well, transistor.. or optocoupler is just like a relay to me? any difference to the reed relay?

author: ElektroQuark
author_rank: Unknown
timestamp: July 30, 2010, 08:14:25 am
content: Reed relay is a real relay, a mechanical one.