LC meter that only measures capacitors

[sanjubluerock3]

my lc meter isn't working i am only able to measure capacitors "C" but not inductance "L"

i have attached schematic, board layout and pcb layout

when i switch from "C"
to "L" its says over range... but where as i am able to measure capacitors...



plz help me..

 

[karesz]

LC meter

Hi,
Did it some one working pls?
I dont know these circuit, but seems me that your Lx will be connected in serie with the 82uH_maybe that is too much for the measuring system & gives overflow?...
K.

Added after 40 minutes:

I found just a description/adaptation of your circuit : **broken link removed**
In text, bottom of the side; over calibrating etc. is to read:
http://www.marc.org.au/ "Over Range - Don't be alarmed if you see this indication. It is normal for the meter to display this when switched to inductor and not having an inductor connected to the terminals."
I think thes is your case too!?
K.

 

[pranam77]

Re: LC meter

The said project of LC metere is available here with complete description, codes, and PCB layout. You may go through it and try to debug it yourself.
**broken link removed**
Cheers

 

[karesz]

LC meter

Hi Pranam,
as you can see too: it must be not a failure_(I think) only understandings problem of an equipment(by first starts)...
Maybe has Sanju never applyed a short to the Lx/Cx contacts & didnt calibrating/zeroing for "L"!?
K.

 

[sanjubluerock3]

Re: LC meter

thanks a lot....i ll refer the link and check my lc meter ....

 

[karesz]

LC meter


Im waiting with suspens on your refering!
Tnx & greetings!
K.

 

[pranam77]

Re: LC meter

Hi Pranam, as you can see too: it must be not a failure_(I think) only understandings problem of an equipment(by first starts)... Maybe has Sanju never applyed a short to the Lx/Cx contacts & didnt calibrating/zeroing for "L"!?
K.

Yes..karez..i agree with you..Actually its a cute n nice design constructed and worked by many many people even today. I am personally using this design without any problems since 2 years now...anyways, we'll wait for "Sanjay" response..
Cheers

 

[karesz]

LC meter


Yes,
After some delaying :-(, yet I can remember, that in the so past 5 years I meat it in lot of versions on diverse HAM & other hobbiest sides ...
Ciao
K.

 

[sanjubluerock3]

Re: LC meter

still i couldn't troubleshoot i am able to measure only capacitor value...
when i switch to L it says over range...

donno whats the prob i even changed the relay thinking that it might have gone bad..even the the prob exist

i have used 12v relay


shall i upload the pic of my lc meter ???

 

[Ruslan_Windrivers]

Re: LC meter

i have used 12v relay

shall i upload the pic of my lc meter ???

12v Relay is unusable in this meter - max battery voltage is 9v, and as it is now, it even connected to 5V - so it won't work.

I would suggest, if you'll be unable to fix your meter, build a much better meter using the almost the same components (just few more will be needed). I just posted the English manual for the meter - see for yourself.
They do not sell them anymore (it wasn't supposed to be commercial product AFAIK).

 

[karesz]

LC meter

Hi,
I can not agree, than the most 12V relays are good working on 9V, OK its not optimal, but with a new like battery , most time they are OK, & these meter has a external or wall adapter forseen...
Both relays are connected direct to 9V, also can be working.
Otherwise I have seen yet that K2 (& S2) has a serial 1K Ohm, i dont understand that, & see it as not needed, or can/must be a lower value!!
@sanju;
can you test it pls? are the relays right switching over, especially K2, the L/C modus switcher?
Concret, you must check pls the datasheet for nominal current & is for that a serial resistor needed (or can be applyed) or not...
K2 would need a diode too...
K.

 

[mvs sarma]

Re: LC meter

That resistor was planned in case you use 5V relay and its value can be adjusted for the current needed.
the relays were shifted to 12V line to reduce interference due to back emf on 5V line.

Diode across K2 is planned already in the schematic and artwork.

 

[karesz]

LC meter

Hi mvs sarma,
The basic function of these 1KOhm is clear me, but not in situation if its a 12V relay used from 9V_or even 8V or 6VType--it will be more clear with some smaller value, this was my reason to write what you are reading...
You are speaking over what kind of schema & artwork pls?
Greetings!
K.

 

[mvs sarma]

Re: LC meter

Hi mvs sarma,
The basic function of these 1KOhm is clear me, but not in situation if its a 12V relay used from 9V_or even 8V or 6VType--it will be more clear with some smaller value, this was my reason to write what you are reading...
You are speaking over what kind of schema & artwork pls?
Greetings!
K.

the design mod was by me. I should have called it test selected
instead of calling it 1K

 

[karesz]

LC meter

Hi,
welcome!
OK, sorry_I didnt know...
If you means the 1K serial on the relay, yes its pro examplar to select, but with 12V relays on 9V battery: you will need surly nothing_maybe some higher battery voltage!
Greetings!
K.

 

[mvs sarma]

Re: LC meter

after having made the PCB, if one has a 5V relay , he/she should have a chance to manage it on 12V line and , it is here the resistor comes to use.. As already commented, I should have called it Test selected value to suite the relay.

 

[karesz]

LC meter


clear me!
It was not a critic of the design, but a notice for these rebuilding only_apart of missing diode on these relay too...
K.

 

[sidy50]

Re: LC meter

Hi...
i have already built the same project, although its not an accurate LC meter plus u
require a lot of debugging i the circuitry...

The very 1st thing is that u should check the switch("The one used to switch between L & C") connection in the circuit thoroughly...i had the same problem but got rectified after properly connecting the switch terminals...

Also its not a matter of relay...Once u switch on or Reset the relays ticks once and takes the reference frequency by parallely connecting the 82uH inductor & calibration capacitor....

 

[mvs sarma]

Re: LC meter

@ Karesz,
if you see the circuit uploaded by sanjubluerock3, the relay Calibhas a diode across the coil as it is expected to be operated by the transistor. Perhaps other one it is not needed as it is manually switched. Hope, this clarifies.

@Sidy50,
Regarding the accuracy ,i feel, (not being the designer, that the accuracy depends on various factors. like
1. clock frequency of 4MHz.
2. the tolerance of the two 1nF capacitors and the actual value and quality of the 82uH inductor. It is specified that one has to use either styroflex or polyester (box) capacitors of at least 2% accuracy. these are available at some cost from Farnell.

The values can be tuned in practice to ensure that the frequency F1 ( measurable with tying a1K resistor between LCD pin D4 and ground) lie below 2^16 (65536). otherwise there is problem of "over range"

I have this meter on the same board i designed and reads 2.2pF between 2 to 2.3
and 47nF is read around 46
a known 3.3uH inductor reads around 3.2 and 22mH is read as 21.8 or so.

Phil rice has provision for slight adjustment in measurement by increase or decrease and thereafter the values of correction are stored in the eeprom.
A grounded 1K resistor is to be connected to LCD D6 or D7 pin for the respective tests.
i have not incorporated these as it is a one time measure and most engineers and hobbyists can do it and later forget. Use of tantalum cap at pin1 of the chip, and other precautions are to be observed.

All of know that accuracy of ant instrument is not by accident. Accuracy, is to be obtained by proper components and software tuning.
For more details I suggest to see the Phil rice's site.
**broken link removed**


I didn't get you on your comment "on the L_C switch" implemented by relay. As already clarified
the 1K resistor in series is a test selection for using lower voltage relays to work on 12V. if your voltage is 9 to 12V DC perhaps it can be shorted out.in case of 5V relays, select value as per the coil current need as per there datasheet.

If you find any artwork I welcome you to indicate the same for further analysis. All the best

 

[sidy50]

Re: LC meter

@mvs I completely agree with you regarding accuracy of the LC Meter...since i built this circuit on PCB...thats why alot of factors could be considered for getting inaccurate results.... I also debugged the same circuit on a PCB created by my friend( which i would say the worst designed PCB i have ever seen)...Almost each n every fault lied in the PCB....But finally got it working The LC switch i was talking is the switch that is used to switch between unknown L or C to be measured Also a normal 6V relay could be used & drive it through PIC using npn transistor I wonder how u get such accurate results...can u measure Inductors in nH range....If possible please post ur designed PCB