tunning of sensor

[Novic]

congratulation you have success to make long range locator electronic, for gold is depend on your frequency you use, for gold I suggest 5 Khz
until 7,5 Khz square wave, but I don't know a circuit you make it's use frekuensi or magnetic respon.

[Iftekhar]

tunning of sensor

Hello,
As you have mentioned,i followed the following procedure
1- I connected up my sensors with a RF generator using a resistor.
2- I Adjusted the RMS amplitude of the AF generator to get 100mV
3-Ran the spectrum Lab program and started the AF generator at 500Hz
4- now I kept the RMS amplitude as set earlier and increased the frequency to 1000hz.
5- I kept on increasing the frequency to 5000hz.
6- i got max peak at 3500hz (-46.o32)
7-Now i added capacitor of different values in parrallel , again set the RMS amplitude to 100mv and ran spectrum lab and started the AF generator at 500hz and kept on increasing frequency to 4500hz while RMSamplitude is only once set at 500hz.
8- AT capacitor value of 940 nF I got max amplitude (-35.200) at my desired frequency
(1916.5)

I have placed the sensors away from building using 12m long microphone cable. you mentioned that cable wil also add up to capacitance but I am getting capacitor vallue on higher side (940nF).
I am really very much upset and do not know what to do really .
With this tunning capacitor i have try to use Phil cct but did not get any results.
Plz guide me if you have any amplifier cct . why this cct is not responding . i am hpeful that sensors are wokring then where is the actual problem?
Time is running out for my project plz do help as mucm as posible.

[Willy Bayot]

Re: tunning of sensor

You should now carefully test your amplifier chain alone.
Feed the amplifier input (not connected to the sensors) with a very weak (1µV) sine wave signal coming from an AF generator. To precisely get this RMS amplitude of the input signal, make a resistance bridge of 100000/1 ratio and measure the AF generator RMS value with a scope.
Connect the output of the amplifier to the Spectrum Lab adjusted to show a vertical scale graduated in mV instead of dB. (It would first need to be calibrated from a signal of known RMS voltage.)
You should then clearly measure the total gain and the SNR of the amplifier. By modifying the injected frequency of the sine wave, you should also see the filter band effect.
Try this first.
Willy

[Iftekhar]

Re: tunning of sensor

Dear Willy
With reference to the Email sentences quoted

"In principle, when the two sensors are connected in opposition without any
magnetic influence around them, you should get a sine wave of 1916Hz lasting
around 2 seconds WITHOUT variation of amplitude."

well the two sensors are differential so they will cancel the effect of each other then how come the sensors will give output frequency of 1916Hz lasting for two or three seconds...

and another one is
there is an output signal
of 1916Hz as well but WITH an amplitude beat whose frequency increases with
the value of the sensed difference (the gradient).
how come the frequency increases i think you want to write Amplitude here... isn't it

[Willy Bayot]

Re: tunning of sensor

For the second remark :
This mag makes a SUBTRACTION operation (DIFFERENCE)and not a MULTIPLICATION of the two signals. With a multiplication, you would get a signal whose FREQUENCY would be the difference between the frequencies of the two sensors.
Here, I meant the frequency of the BEAT.

For the first remark:
Theoretically, if they were EXACTLY at the same frequency (absolutely no gradient), there would be no amplitude beat but as the amplitude of the two signals are never exactly the same, the result of the subtraction would be a signal at 1916Hz with a small amplitude. However, in practice, there is no chance that the two signals have exactly the same frequency, thus there will always be a VERY LOW frequency amplitude beat (that you will not be able to hear)

Willy

[Iftekhar]

Re: tunning of sensor

Dear Willy
I have tested the whole circuit it is working fine on 5uV signal and giving the frequency signal much much amplified but comparatively with a very low noise level.

I connected the sensors in a differential configuration and configured it to the near by frequency but the frequency that the spectral lab program is giving is a wide band of frequency. it is giving a peak at 1896HZ now could u guide me how to remove the band of frequency except the one i am looking for i will try to configure it to 1916 later on. but the main problem is the band.

Secondly Which size of ferromagnetic material or Magnet do i Use to get a detection on my sensors and how far away from the building will the sensors + electronics circuit be place to get the clean signal. about the orientation of the sensors

Phil wrote that the sensors must be on the east west plane but what about the sensor individual itself in which direction the head of the bottle be pointed to...

About the power supply we cant carry an AC to DC power supply far away from the building so which portable power supply would u recommend to use to Polarize the sensors.

[Willy Bayot]

Re: tunning of sensor

To expand (zoom in) the frequency scale, put your mouse cursor on the frequency scale at the frequency you want to zoom in and click on right button. One of the pop-up menu entries will say zoom-in. Click on it. After that you could zoom-out the same way.
Do not put a magnet or a large piece of iron too close to the sensors otherwise the signal will disappear. Try to put a piece of iron of 1 Kg at a decreasing distance starting at 5 meters or a car starting at 50 meters.
You must be at least 5 meters away of buildings, large iron or steel objects and power lines.
The bottles can be pointing in any direction but they better be horizontal to get a maximum signal.

You can use any lead-based battery. Car, motorcycle for boat usage on sea wghere the weight is not important or better, gel cel types with a sufficient amount of AH. Ordinarily, 1200 mAh gel cel are quite sufficient for portable use without being too heavy to transport.

Willy