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PIC-controlled LC meter: Working now, pictures inside!

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Dr. Shark

Sun Feb 19 2006, 08:11PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

While surfing the web I came across

, a description how to build an LC meter which is, unlike most cheap commercial LCR meters,good for very small inductances, like they come up a lot in the stuff we like to play with, namely TCs, or even Class E TCs. From the description is seems that it is quite simple to build, basically its just the PIC, a hd44780 display and a few off-the-shelf components. Its been years since I have been doing PICs, but this seems simple enough to get back into it.

Has anyone build this thing?

Would anyone like to build this think (common, you know you want!) and send me a spare PCB while he is at it (kidding, I am hoping to to my own PCBs soon.

Anyway, let me know what you think about this, it seems like a fun and useful project to me!

Marko

Sun Feb 19 2006, 08:14PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I really doubt it works as good as profesional multimeters, but for a toy it can be used :)
But for shematic, says 404

Dr. Shark

Sun Feb 19 2006, 08:26PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Fixed the link. It is supposed to be accurate to 1%, also the digital display readout looks really professional. Most meters you get for 100â‚¬ or so only go down to 1uH and cannot even get close to the nH range of this meter. Only the really expensive bench LCR-meters that even cost 1000s of â‚¬s used measure these low inductances.

HV Enthusiast

Sun Feb 19 2006, 08:30PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

I actually have one of these, although i purchased it as a complete kit.

I found it to be extremely accurate and was in fact even better than some of the professional meters out there (i.e. BK Instruments LCR, etc...)

Its a very good design!

Marko

Sun Feb 19 2006, 08:52PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

yep it seems nice, but I dont know will I really need one even in future, now i MUST grab some kind of osciloscope, any...

Wolfram

Sun Feb 19 2006, 09:17PM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

I built it around a year ago, but I never got around to put it in a case. Accuracy seemed to be good, but I didn't test it against any commercial meters.

Dr. Shark

Sun Mar 12 2006, 12:14PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Since I can't do PICs and PCBs, I ordered a kit of eBay which contains both and the LCD for 20â‚¬ and put the thing together. It works marvelously:
First picure: Measuring the inductance of a TC primary coil:

Second: The PCB, note how neat and simple it is: Only three active compnents!

And third, measuring the capacitance of a TC topload against ground:

Note how the capacitance reads much higher than the calculated 5pF, no idea why that is.

Operation is very simple, you switch it on, push the "zero" button to calibrate it, and conntect the DUT.
Assembly was also a piece of cake, took me a couple of hours because I salvaed a lot of the discretes from other PCBs, but when I switched it on in worked right away.

The thing seems to be really accurate for hobbyist purposes, for TC secondarys it agrees very well with calculated values, and for capacitors it is usually in the tolerance range of what the label of the cap says. The range of capacitances and inductances it measures is very well suited to TC and other HF stuff, most cheap LCR meters can't do this.
Since I did not have a project box at hand I just mounted it on an acrylic L-bracked, how stylish is that?

If you are interested, this

is where I got it. Shipping was a fair 4â‚¬ throughout europe. Seems the price has gone up a bit, but for people like me who can't do PICs and PCBs I guess it is still well worth the money. (No, I am not affiliated with the seller, I am just sharing my personal experience here)

HV Enthusiast

Sun Mar 12 2006, 12:26PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Excellent - very nice. Didn't cost much either!

Sun Mar 12 2006, 01:50PM

Registered Member #85 Joined: Thu Feb 09 2006, 01:22PM
Location:
Posts: 21

Jup, you got a very nice meter.
Thinking about the reason why your toroid reads higher capacitance than calculated, I believe this could be due to the proximity of it to the table (ground). In normal condidtions it is on top of the secondary and therefore further away from ground, which would cause a lower capacitance.

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