delta pulse more sensitive to gold delay reduced

[ossamaussama]

to make delta pulse work with lower delay

need to reduce the effect of feedback network on delay sample

by inserting 50k

and the gain have to be reduced

so use pot 100 k instead of 20 k

to ensure stability

and use 300 hz instead of

100 hz


try it and its work

now it can detect small gold

http://www.geotech1.com/forums/attac...1&d=1322337584

[Geo]

Yes, but if the delay is <= 30us then you need to shield the coil.

[ossamaussama]

Yes, but if the delay is <= 30us then you need to shield the coil.

will be tested in ground

for small gold that cannot be detected before

[Jose]

I agree with you ossamaussama
We must make a quick shielded coil (Scotch tape No. 24)
No nesecidad to reduce the gain, but increase to 1.5 K. R6
regards

[ossamaussama]

does any one know what cause beating at integrator output in delta pulse

that is voltage goes from -.15 to .37 in slow beating

[Jose]

It could be due to interference of the electric network Energia.
Adjust the TX frequency to see if it reduces the effect.

[ossamaussama]

no i try outside home no near electric line


check with analogue voltmeter

you will see beating

slow but exists


i need to remove this beating in order to

use another VCO circuit that have clike sound and when metal is near sound change

you know it is like palse star sound

i try it it can detect 1 euro at about 50 cm

but the problem in beating make it not stable

[Jose]

I will perform the same test, far from the electric line to see how does my DP.
50 cm for a currency is a very high sensitivity.
I found that most of the problems of instability, increasing R6 improved, the value is 1.5 to 2.2 K. The delay setting is softer, you can use lower inductance coils (400 uH), although the sensitivity decreases slightly.
Another notable improvement is to incorporate a trigger circuit for the IRF740, with an integrated 4427 or similar.
We also need to adjust the damping R for best results.
My DP is just over 40cm for a currency.

[ossamaussama]

thanks jose
increase R6 to 1.5k give more stability

[pigeon]

hi



I have to change the resistance6 value of 680R by another value 1.5K?

[ossamaussama]

note

in original design it was 680 and keep in mind delta pulse is designed for large deep object

not small


make it 1.5k will increase stability as Jose said

but i don't know effect when using large coil


any way it is experiments

you have to try

[Jose]

hi



I have to change the resistance6 value of 680R by another value 1.5K?

If, whenever "R6", in some schemes Figure 680, in other 1K.
Jose

[Jose]

in original design it was 680 and keep in mind delta pulse is designed for large deep object

not small


make it 1.5k will increase stability as Jose said

but i don't know effect when using large coil


any way it is experiments

you have to try

I performed large coils of 1X1 meters, equal to 1.5 K. R6
Is more stable.
We must reduce the TX frequency between 150 ... 170 Hz
Increased to 200 usec. the width of Pulte TX.
I use 12 turns for coil 1X1 mtrs.

Roll 45X45 cm. I use 18 laps.
Frequency .... 550 650 Hz
Scotch tape Blindage No. 24
In all cases, reset the value of R buffer.
In all cases, R6 = 1.5 K.
Greetings Jose

[ossamaussama]

more depth

who notice that using more gain in large coil will reduce the depth??


at last i found the Reason for that

it is because more gain before integrator will cause fast retuning

so deeper target will eliminated by re tune circuit

my idea is to reduce the gain before integrator by use larger
the potentiometer 20 k have to be increased

and use the following circuit

which is 2 stage non inverting amplifier

tested already with 1M coil

and the target was aluminum coca can

which is easily detected at 1.7 meter good sound

[Jose]

It's very interesting what you say, I did not experience it.
Large coils tend to be unstable and require more transmission power.
I can not explain the razan theoretical but real.
It seemed to work best with low frequencies in the ground.
My MD detected in the air more than 1.4 meters from a soda can of 333 cm3.
The same can of soda is detected at 1.1 meters below ground.
The higher frequencies work well in the air, but not in the field.
Coil 1X1 m.
Jose