Question for Reg, about induction meter.

[Frank-S]

Reg, over the winter I made a lot of coils. some worked good, some not so good.
I used a hom meter.might need to try a induction meter to get better results.
Question how does a induction meter work.
Is it used like a hom meter or do you hold it next to a coil like a transformer with out
a core to get induction.Does the detector have to be turned on.
Thanks

 

[Reg]

Hi Frank,

An inductance meter works much like a basic OHM meter. It has two leads that connect to the coil just like you would do to measure the resistance, except the meter has the ability to measure the coil's inductance.

There are a wide range of simple portable inductance meters (normally called LCR meters) available that span a cost of $20 to over $300 or so. Personally, I have several and I have found I get very similar readings with the cheap ones as I get with the more expensive models. Some of the cheaper models are not quite as accurate in the fact they won't read quite as precise but still will suffice for most applications.

If you go to Ebay and search for LCR meters you will get a full range of meters to chose from. Keep in mind that a typical LCR meter will also measure ohms and capacitance. So, they are more versatile than a simple OHM meter.

Reg

 

[Frank-S]

Reg, Thanks
Frank.

 

[Sven]

I bought this one off ebay pictured below. It works for me. Look for this one with the 4 buttons. It can also operate of a AC/DC 5 volt adapter. Or run off your PC's USB power with the cord supplied
From the listing
modle:LC100-A
Size: 81 x 47 x 30 mm ( L*W*H )
Supply power: +5v ,mini USB interface
Measurement accuracy:1%
Capacitance measuring range: 0.01 pF - 10uF
The minimum resolution: 0.01 pF
Big Capacitance measuring range ：1uF-100mF/minimum resolution:0.01UF
Inductance measuring range: 0.001 uH - 100mH
Big inductance measuring range: 0.001 mH - 100H
The minimum resolution: 0.001uH
Test frequency range: L/C about 500KHZ/Big inductance 500HZ
Effective display digits: 4 digits
LCD display mode: 1602

Becareful of the handheld ones that look like a multimeter. May claim to have an inductance measurement, when you get them, they don't or if they do resolution is not close enough.

 

[Frank-S]

Thanks Sven, I dont have a acount with ebay.they have some good low price's.I dont mind
sending a money order, but ebay and pay pal wont to much personal information.I will see what
I can find here.if not I can do with out.
Sven I posted a formula for a coplanar coil that I used on a 8"coil.tryed useing it on a 16" coil,it worked
but not very good.I guess different size coils need different formulars.
Thanks for the picture

 

[Frank-S]

Hi Reg,
I am unable to find a simple to use induction meter here.Do you have one
that I can purchase that you dont need.If you do. E-maill me.
fjs5015@yahoo.com
Thanks Frank.

 

[Reg]

Hi Frank,

I don't have any LCR meters to sell but you might try checking for LCR meters at Amazon. They take credit cards or possibly another means of payment. They have LCR meters ranging from about $20 and up. I have one of the $26 red units and it works fine even though some of the reviews are not that great. In fact, my $26 unit matches my two BK units, which are the 875 and the 878 and these cost about $200 and $279 or so.

For most of your work, a cheap one will probably do well for you. Now, I should mention that my Red unit that sells for $26 does act up once in a while but that is because of the cheap meter leads. Wiggle them or pull them out and reinsert them a couple of times to make better contact eliminates the problem.

Keep in mind that the LCR meter recommended by SVEN requires a computer with a usuable USB port and since you are using a public computer at a library, I would pass on the model he mentioned even though it can be purchased on Amazon also.

Reg

 

[BeyWolf]

I have been using a $50 LCR meter for the last 6 years with no problems.
It's made by TENMA and I bought it mail order from MCM Electronics.
They don't have the same model as mine anymore but they do sell a $40 and $50 LCR meter.

 

[Frank-S]

Beywolf
Thanks MCM electronics has one I will give them a phone call and
see if I can order it over the phone.

 

[Frank-S]

Reg Thanks
MCM has same LCR meter as Amazon.I will call them if they will
sell it on the phone I will get one.
Frank.

 

[Sven]

Hi Frank,


Keep in mind that the LCR meter recommended by SVEN requires a computer with a usuable USB port and since you are using a public computer at a library, I would pass on the model he mentioned even though it can be purchased on Amazon also.

Reg

Does not require a computer, it has the option of using the computer USB power or just a plain ole 5 volt AC/DC adapter

 

[Frank-S]

Thanks, I ordered a Tenma 72-8155 LCR meter yesterday from MCS Electronics.
BeyWolf,Reg, Sven. I won to thank all for your help.Now I need to learn how
to use it.
Reg,BeyWOLF, If you have some coil induction numbers,TX and RX readings
for differance coils.that has good dept,dont need name of coil.it will
help me figure out how to use inductions
Frank.

 

[Sven]

Thanks, I ordered a Tenma 72-8155 LCR meter yesterday from MCS Electronics.
BeyWolf,Reg, Sven. I won to thank all for your help.Now I need to learn how
to use it.
Reg,BeyWOLF, If you have some coil induction numbers,TX and RX readings
for differance coils.that has good dept,dont need name of coil.it will
help me figure out how to use inductions
Frank.

There was a whole listing somewhere on Geotech, any coil in particular your looking for the numbers?

 

[BeyWolf]

Hi Frank

The TX coil is usually part of an Oscillator Circuit that also includes a capacitor.
The values of the coil and cap will determine the operating frequency of the detector.

Any detector circuit will be designed for a small frequency range, so the coils and other components are chosen for that frequency.

Depth is usually achieved by making the coil larger in diameter.
The reason some of your coils worked better than others is because they were closer to the correct inductor values which are measured in henrys.

When you get your LCR meter, you can measure the two coils on the factory made search-coil that came with your detector. Then try to make your coils with the same value.
You should be able to find the pinout for your search-coil somewhere on the internet.

Like Sven said, the Geotech website will have most of the information you need.

I hope this helps.

 

[Frank-S]

BeyWolf.
Question.
A coil with a cap,is the cap in line with windings,across a resistor,between TX and RX
coils. Can you tell with LCR meter.
I am tinkering with a 13" coplanar.I found out also that size and restance of RX coil has to
do with dept and sensitivy.I started out with a 4" Rx coil .8 ohms dept US nickel 2"
silver dollar about 4". I am up to 3.9 ohms, dept nickel 11" silver dollar noise 14-1/2''.I haved
about maxed RX ohms out.next, make coil larger.
Thanks Frank

 

[BeyWolf]

Frank

The capacitor I mentioned is probably located on the circuit board inside the control housing. It will be wired in parallel to the coil when the coil is connected.
Sometimes they use 2 caps with a center ground. Don't worry about the capacitor.

The low ohm DC resistance that you're measuring across the coil has almost no effect so you don't need to bother measuring it.
When it comes to coils it's the inductance that matters.

If I'm wrong about this I hope one of you electronic designers will correct me.

I'm sorry Frank, I don't have the knowledge or experience to help you design coils for your detector.

I do have basic analog and digital electronics knowledge and I have designed and built my own pin-pointers.
One of my future projects is to build a PI pin-pointer. I'm hoping I can get some help when I get started. I plan to do a lot of homework before I ask for help.

 

[Frank-S]

BeyWolf
Thanks,It does matter about ohms reading in Rx or TX coils.I have been expermenting all wenter
as to what works and dont work in a detector coil.it tell's me how many turns of wire to put in each coil.
I am not school trained in electronics,so I do and see things different.To me a detector coil is like a stept
down transformer with no center core.Tx is primary Rx is secondary.
I have made a fue pin-pointers in the past,one for a CS-6 PI and the PI that I have now,they both worked.
If I change connectors the pin-pointer will work on both PI.A pin-pointer is easy to make.it has a ferrite
core no air core.If you have a ferrite round core about 2"x3/8"or 1/2"any size round ferrite might do.
To start take about 18 feet of number30 or 31 wire,tape ferrite core,leave about 4'', wind wire ramdon
on one end of core.about 1"long untill you get to end of wire,leave another 4"tape windings tight.you have 2 wires
if you have a PI connector and cable ,connect 2 wires to 2 wires on cable.its ready to test to see if it
works. NOW, if it dont work,take a fue turns of wire off untill it workes,then take 1 turn of wire off untill
you max out dept that you wont.You should be able to detect a US nickel a 5" or better.
As you can see I do things different.
Frank.

 

[Frank-S]

Hi BeyWolf.
I wont to apologize about my last post concerning PI pin-pointers, I posted the wronge
length of wire to start with,before makeing adjustment.
I found a open pin-pointer at home with its wire exposed that I was tinkering with for my
Piranha PI.years ago.It still worked,it will detect a US nickel at 5" and a small nuget 1"
not to good but it works.inductance-1.21 mh.#30 or 32 wire. wire is 24ft long.
I apologize for posting wronge instruction.I made a picture copy of it on a copying machine
if you wont me to post a copy, I will ask the libary-an to post it.
Frank.

 

[BeyWolf]

Hi Frank

Thank you for sharing the information on coils. My plan is to build a complete stand alone handheld PI unit like the DetectorPro Pistol Probe or Vibra Probe.
The last probe I made has features similar to the Garrett Pro-Pointer.
I hope you got your new LCR Meter and find it useful.

 

[Frank-S]

Hi BeyWOLF.
I have the LCR meter.It works OK,Its a new Toy.Useing the LCR meter for the first
time is like being out in the Ocean with a GPS and no numbers.
I was working on a 13" coplanar coil useing Ohms,had it working OK with Ohms.Now
I am tinkering with a 18'' coplanar coil useing mh inductance numbers, it works,not to
good.I supect that larger the coil,it takes different induction numbers.
I am glad that I dont do this for a live-ing.
Frank.