Accurate LC Meter Kit

Update (6/1/12): Not having heard back from electronics-diy.com, on 5/29/12 I inquired by email about the assembled kit I returned. The next day I received this reply: “We have done a range of tests on your LC Meter kit and have found no problems. Both capacitance and inductance measurements are identical to our kit. We even used brand new microcontroller chip and the readings are the same. Per your request we can either ship the kit back to you, or if you are not fully happy with it offer full refund.” I asked for a full refund, which they promptly granted (minus $5 shipping that I initially saved when placing an order over $99, but now have been charged since my return brings that order under $99).

Update (3/7/12): Yesterday I prompted support@electronics-diy.com for a reply, mentioning the number of pageviews this post has received. I received a prompt and polite response. I learned that I was mistaken in expecting the meter to read capacitors 1 uF or higher, since the published range of the meter is only 0.1pF-900nF. There was no explanation of why I am having problems with inductors that are within the published range of the meter. However, I was quite favorably impressed by an offer to test and fix the kit at no extra charge! I shall take them up on this offer and keep you updated.

Update (2/8/12): I am having trouble with this LC Meter. It gives me the same reading for all capacitors 1 uF or higher, and the same reading for all inductors higher than about 70 mH (this last value is just a guess): 838.8 nF and 83.88 mH, respectively. As you can see the digits are the same. It seems to work for really small capacitors and inductors, but anything bigger and these are the only readings I get. I emailed support@electronics-diy.com on 1/8/12 about this, but as of 2/8/12 I have received no reply. Unless and until I learn the problem is due to some error of my own in constructing this kit, I recommend against purchasing it.

Yesterday evening I finished building the “Special Edition Accurate LC Meter Kit with Blue Backlight LCD”, available from Electronics-DIY.com for $69.95. I have no experience with such devices; a more experienced fellow told me he was impressed by its specifications, so I ordered the kit. Soldering it up was a snap. The main printed circuit-board is all through-hole construction, and the LCD-board that mounts over the top of it requires nothing but a connector.

If you want to build one of these you may want to order this version of the kit instead of the one I purchased: Accurate LC Meter Kit with Green Backlight LCD, for $59.95. My kit’s “Blue Backlight LCD” turned out to be green anyway, and I think the two kits have the same circuit, save an adjustable potentiometer on mine that controls the contrast of the LCD (which I just set to maximum anyway). Certainly the cheap case that comes with the kit I ordered is not worth the extra $10 — to use it you have to carve out a bunch of stuff (to make room for the circuit-boards), including two of the four stanchions that attach to the lid. After going to all that trouble (I used a Dremel tool) you are left with a case that requires adhesive tape to hold down one side of the lid!

The instructions that came with the kit were pretty sketchy, mostly limited to how you need to carve up the case (by the way, the measurements were wrong, so ignore them). The only thing that got me into trouble was the voltage regulator, which gets in the way of the LCD-board (and protrudes too high to seat the lid of the supplied case) if you solder it in the way you normally would (which I did!). By bending the voltage regulator out at angle I managed to get the LCD-board mounted, but the lid still won’t seat properly. Learn from my mistake, and bend the leads of the voltage regulator into a Z so that they lay flat on the board and allow the voltage regulator to sit just off the edge of the board. (Of course, this only matters if you try to use the case provided.)

You’ll need to supply your own power to this unit. There isn’t enough room in the case for a 9V battery, so I purchased a DC socket. You’ll also need to supply your own connectors for testing inductors and capacitors; the photograph on the Electronics-DIY.com website shows them in the case, but they aren’t supplied. I used banana-plug sockets. You’ll also need to supply your own pin-connectors if you use the supplied pins on the circuit-board, and you’ll need your own stand-offs if you want to support the LCD-board (only two of the four screw-holes match up with the lower PCB, but that’s probably good enough).

There is no way to select the units displayed on the screen, e.g. pF vs. nF. But the dearth of selector switches is actually one of the nice things about this unit. There is no need to select a range of capacitances or inductances. The only thing you have to do is plug it in, hit the reset button whenever you want to calibrate it, and stick in a capacitor to get a reading. If you want to test an inductor, you simply press one button to select inductance-mode, then attach your inductor. It just works — and it works with precision.

Here is a slideshow of some snapshots that I took with my cell-phone. They didn’t turn out very well, but they’re good enough to give you an idea of what it looks like. Notice that I used black electrical tape to mask the edges around the LCD. That’s because the opening I made was downright ugly. Next time I’ll try using a cutting wheel on my Dremel tool instead of a grinding tip!

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8 Comments

Filed under Kit Building, Test Equipment

8 responses to “Accurate LC Meter Kit

  1. Good morning it sure does seem for a kit that there was a lot of mod’s that had to be done. A case for 10.00 and in the end having to hold it together with tape is not good at all. I hope there was an email send to the company to bring this to their attention! In theory the kits seems it can be useful but for all the troubles you had to go through and modifications seems better to just go and purchase a commercial unit ….or look for another kit. Thanks for the review.

  2. Todd Mitchell

    You’re welcome, Mike. You might be right. I simply don’t know how the performance of this meter stacks up against other ones. The version of this kit that comes without a case may well be a good buy.

    I hope to write up another kit from this same company — a signal generator that I’ve finished soldering up and just need to mount in a box.

  3. George

    I just checked their web site and it says the case comes free. It seems that $10 difference you pay for are for high precision calibrating caps & inductor, better quality through-hole PCB with red solder mask, metal film resistors, machined IC sockets, gold plated header pins and contrast pot. It seems like a good quality kit to me. For commercial LC Meter be prepared so shell a couple of hundred bucks and I am not sure they can measure inductance as low as this one. Just my two cents.

    • Todd Mitchell

      Thanks for the comment, George. I compared the parts list on their website for the two versions of this kit. They show that all the parts are identical except for the LCD (which turned out to be identical anyway), but I don’t know if the parts list is reliable since it actually shows a contrast pot in the cheaper version (which isn’t on the pictured PCB). Is there a significant difference between red vs. green solder mask? If so perhaps it’s worth the extra $10; I’m ignorant about this.

      I agree with you that this is a good deal; we just have to look past the obvious gaffs. I think the company who built this kit did themselves a disservice by sending a case with it. Most of their kits don’t come with cases – I also built their signal generator kit, and it’s up to me to encase it. Leave the case out, and you have an excellent kit here. You can purchase LC meters for less money but they’re only around 5% accuracy — this one is at 1%, and far more sensitive, too.

      I would definitely recommend this kit to folks, but only the cheaper version — not so much to save money, but to avoid the temptation to use the “free” case.

      Thanks again for the comment. If you build one of these, let us know how it goes for you.

  4. George

    No problem Todd. The color of solder mask doesn’t really matter. Some folks prefer red because it just looks better or because it is associated with better quality boards. Their PCB with green solder mask looks like it’s a standard single layer board to me with no through-hole plating. The red one looks like it’s a two layer with plating on it so these boards are made with better quality PCB material and solder mask is normally applied on both sides.

    • Todd Mitchell

      Good eye, George! I hadn’t noticed that. You’re right about the through-hole plating on the kit I purchased.

      Thanks again for taking the time to contribute your insight. Comments like yours significantly improve upon the quality of this blog.

  5. Pingback: 1Hz-2MHz Function Generator Kit | Elmering

  6. Geoff Cronyn

    I too built the accurate lc meter….excellent kit, but I didnt use the case! The only problen I had was when I powered it once with a 12 volt PSU which had a faulty smoothing cap. This damaged the 16F628A, now that it has been replaced, I cant find a copy of the firmware to flash to the replacement PIC. Has anyone a firmware file, or know where I might download one?
    Thanks, Geoff.

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