LC100-A : A precise  LC meter for 3.75$  - Page 1
Forum section: electronics / testgear

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: June 06, 2016, 01:15:06 pm
content: I was lacking a device to measure small caps and I came across this incredible deal on ebayhttp://www.ebay.fr/itm/111926481261?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITI took the chance, order it on May 17, for 3.75$ including postage, and just got it today. It is provided with a decent usb cable, alligator hooks, and seems to work just fineHere are some examples of measure of 1% caps I have.A B (A-B)/Anom. prec. meas.value(pf)33 1% 32.65 0.0113300 1% 3290 0.00322000 1% 21950 0.00210000 1% 9964 0.004I have also some old caps of lower valuesA Bnom. meas.value(pf)12 12.6815 15.3518 18.8427 27.54I must say that I am perfectly happy with this device which is based on STM8S103.

author: lukaq
author_rank: Regular Contributor
timestamp: June 08, 2016, 01:04:45 pm
content: what the?? how is it that cheap? and most countries are excluded from sending to

author: PedroDaGr8
author_rank: Super Contributor
timestamp: June 08, 2016, 01:12:34 pm
content: looks to be a typo. Already all sold out, seller now sells them for $14.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: June 11, 2016, 09:21:47 am
content: Yes you are right, they probably made a mistake in the price when they put it at $3.75.They were fair to send it anyway.I have measured some coils and seem to have problems for low inductance valuesfor the same transformer coil,I get 11.73 mH on the HiL scale and 754 uH on the normal scale. Any hint ?My guess is that the 11.73 mH is the right value as the primary gives 4.47 H and this is a 240V/12V transformer,so I expect that the ratio of inductance will be roughly 400 (20^2).

author: elecdonia
author_rank: Frequent Contributor
timestamp: December 22, 2022, 01:47:02 am
content: It’s time to either bump this old thread in a major way or start a new thread for theLC100-Ainductance/capacitance meter.The LC100-A is widely available from many vendors. Typical price is now $15-25 USD.It is worth every penny!While many LCR meters are offered by major test gear manufacturers, most are at least 5-10 times more costly than the LC-100A.The LC100-A is a great companion to the$20 Transistor Testerdevices which many of us already have on our workbenches. A C or L which is difficult to measure accurately with one of these devices might be measured more accurately by the other device. This is because the measurement technology is entirely different for Transistor Tester vs. LC100-A.I have been using the LC100-A for several years. It is incredibly useful for projects containing inductors, such as switching power supplies and audio loudspeaker crossover networks. It is equally valuable for RF projects, especially when tuned circuits need to be measured. I first obtained an LC100-A to help me diagnose and restore vintage AM/FM broadcast band radios. This task frequently requires accurate measurement of very small C (1-500pF range) and also small L (5 to 500uH).I will begin by posting links to several detailed discussions of the LC100-A:The following thread from the Antique Radio Forum is a good starting place:antiqueradios.com LC100-A, LC200-A, and similar low-cost digital LC meters?The LC100-A has also been discussed in these other EEVblog topics:EEVblog Other Equipment & Products board: china-lc200a-lc-meter-teardownEEVblog RF, Microwave, Ham Radio board: microwave-tl-coax-impedanceOther links to the LC100-A:VK4GHZ.com LC100-A LC meter modsludens.cl Understanding, fixing, and improving the LC100-AHackaday.io LC100A LC meter fixThis link describes a comprehensiveredesignof the basic LC100-A circuitry which adds capability to measure Q of tuned circuits:(in German but Google will translate)the-dg5mk-lcq-meter-v-2.3Another home-brew version is described in the next link. It uses the Atmel ATmega8515 MCU. The ATmega328 could easily be substituted.http://uzzors2k.com/index.php?page=lcfmeter

author: edavid
author_rank: Super Contributor
timestamp: December 22, 2022, 01:51:55 am
content: The problem with the AADE/LC100-A style LC meters is that they are only accurate for near-ideal components. Parasitics will quickly degrade the measurement. If you have the money for a DE-5000, it's a much better value, since it makes true (phase-sensitive) LCR measurements.

author: elecdonia
author_rank: Frequent Contributor
timestamp: December 22, 2022, 09:00:51 pm
content: Quote from: edavid on December 22, 2022, 01:51:55 amPro” and “lab grade” LCR meters allow the user to select the test frequency.Fortunately capacitors tolerate wide variations in test frequency. However this isn’t the case when measuring inductors. Selection of appropriate test frequency is quite important when measuring inductors. The only control available to the LC100-A user is to selectsmall Lorlarge L.LC100-A test frequency forsmall Lis 50-600kHz. Test frequency forlarge Lis about 50kHz maximum. However this may still be too high for accurate measurement of some inductors.Example: A 60Hz power transformer should be measured with a test frequency in the audio range, no higher than 1 or 2 kHz. Use of an appropriate oscillation frequency is critically important when measuring inductors with cores made of powdered iron or steel laminations. Another factor when measuring large inductors is that a winding with multiple layers of thin wire may possess considerable internal capacitance.The test frequency used by the LC100-A insmall Lmode is considerably higher than when usinglarge Lmode.Generally thesmall Lmode is reasonably accurate for air-core and ferrite-core inductors.However,small Lmode is likely to be grossly inaccurate for inductors with powdered iron or laminated steel cores. In fact even thelarge Lmode may be inaccurate for laminated steel cores.Fortunately pressing the small button on the LC100-A displays the oscillation frequency of the measurement. If this frequency is well outside of the normal operational range of the inductor under test then the displayed test result for inductance is probably inaccurate.

author: bffargo
author_rank: Regular Contributor
timestamp: December 23, 2022, 04:22:22 pm
content: Note that years on now, (almost?) all of these that are being sold on eBay and AliExpress now are the "B" (F?) grade clones that use both the wrong inductor to compare against, as well as other questionable components. See the various discussions linked from the other forums about how to address this when (not if) you get one that isn't close to accurate. Highly unlikely you will find the original run accurate ones from 7 years ago anywhere anymore.

author: elecdonia
author_rank: Frequent Contributor
timestamp: December 23, 2022, 09:35:35 pm
content: Quote from: JacquesBBB on June 11, 2016, 09:21:47 amYes, 11.73mH is likely to be reasonably accurate.If measurement result islowerfor normal L mode compared to HiL mode, this indicates the inductor under test cannot function well at the (much higher) test frequencies employed by LC100-A normal L mode.Inductors and transformers intended for mains frequency operation (50/60Hz) must be measured with test frequencies in the audio range, preferably no higher than 1 or 2kHz. As much as possible the test frequency should be similar to the frequencies the inductor under test will encounter during normal operation.Low frequency inductors/transformers have cores made from a stack of manythin sheets of iron or steel.These thin sheets are known aslaminations. Although some very expensive wide-band audio transformers made with laminated iron/steel cores are functional up to 50kHz or a bit higher, this isn’t the case for typical 50/60Hz power transformers. Their high frequency performance is limited by eddy current losses in the laminated iron core along with stray capacitance in the windings.These can only be measured by LC100-A HiL mode.Another popular core material is known aspowdered iron. These are often painted or wrapped with tape in brightyellow,red,green, orblue,especially when the core has a toroid shape. These are functional up to about 100kHz and are commonly used in switching power supplies.These should also be tested with LC100-A HiL mode.Ferritecores are usually grey in color. They have a much larger frequency range which can extend up to many MHz. For ferrite cores the LC100-A can test them in either range.Coils with no core (air core)can handle extremely large frequency ranges. Either normal L or HiL mode may be used when measuring air core inductors with LC100-A.LC100-A test frequency range for normal “ small L “ mode is between 50kHz and 500 or 600kHz.Test frequency for “ HiL “ mode is much lower, from roughly 100Hz up to 50kHz maximum.

author: elecdonia
author_rank: Frequent Contributor
timestamp: December 23, 2022, 10:00:19 pm
content: Quote from: bffargo on December 23, 2022, 04:22:22 pmI agree thatmostof the currently available LC100-A units come with anunacceptableinductor which has apowdered iron core.Powdered iron cores are often painted bright yellow (or another bright primary color) and are usually in the toroid donut shape with 20-30 turns of wire wrapped in a single layer around the core. Unfortunately the internal losses of powdered iron corespreventthem from functioning well in the LC100-A oscillator circuit.Therefore the first improvement for an inaccurate LC100-A is to replace the factory inductor with a properferrite coreinductor. The replacement inductor may be anywhere from 50uH up to 100uH. The exact inductance value doesn’t matter. It is OK to use 56uH, 68uH, 82uH, or 100uH.What does matter is the inductor must have aferritecore,nota powdered iron core.Ferrite cores are almost always a dull grey color. They aren’t brightly colored. Acceptable ferrite cores may be in the toroid donut shape or in a form known as “binocular” where there are two holes in the core with the wire wrapped through the two holes. I have also had success with “radial” inductors where the core is shaped like a dumbbell with the coil in the middle. Additionally, some of the tiny SMT “shielded” inductors where the coil is entirely inside the ferrite core also work very well. I will post photos of several inductors and provide a simple method to evaluate them for use in the LC100-A.There are two other components in the LC100-A which determine its accuracy. These are the two reference capacitors. However, the capacitors used by the LC100-A manufacturers are generally “good enough” to use without replacing them. The main issue is the (poorly chosen) factory inductor.So, improving LC100-A accuracy usually requires replacing onlyonepart: the inductor.

author: yuzd
author_rank: Newbie
timestamp: May 22, 2025, 08:41:42 am
content: The LC100-A has a calibration mode that activates during startup. Here’s how to access it:Turn off the power.Set the mode to "small C" (make sure all buttons are released).Press and hold both the Zero and Func buttons at the same time.While still holding Zero and Func, turn the power back on.The display will show:measure Cx0pF xxxxxxHz (frequency)Now do the following:Press the L/C button.Then press the Func button.Release the L/C button.The display will now show:measure Cx1000pF xxxxxxHz (frequency)Connect a precision 1000pF capacitor to the input and press the Func button.The device will calibrate using this capacitor and then switch to normal operating mode.All of the above steps were discovered by trial and error. If anyone has more accurate information, please share it.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 22, 2025, 10:27:16 am
content: and the precision of such would be once the inductor is changedseems this thread is almost a sell thread ... i do know theses parts tester can be useful, but precision wise mmmmm, i do use some models but ...they dont do serial or parallel mode ... they are not true lcr tester, not true inductor tester, they dont "ring" coils ....When i see a title with "Precise" in it, do some compare with say de-5000, hantek 1832 1833, uni-t 612 622, zoyi, keysight, ET43x models and more ... even the M4070, or other known cheapo testers@edavid is right ...