Tesoro Bandido III

[pito]

I know why detectors have two synchronous detectors, why does this one have a third one?
Ground balance?

[Aleks85]

Thank you Carl for the clarification.The archive contains all the information on Bandido.
https://drive.google.com/drive/folde...usp=drive_link

[Carl-NC]

I know why detectors have two synchronous detectors, why does this one have a third one?
Ground balance?

Yes, many detectors have 2 channels, X & R, and the R channel is rotated for ground balance. However, this alters the target phase reading. Some have a third "G" channel, which is used for GB so that X & R still give an accurate phase reading.

[pito]

The detector is tuned, the initial phase value = 0 degrees.
Air test;
phase shift of the signal for the object X = 20 degrees.
Field test;
phase shift = 20 degrees + ground phase shift.
If the initial meaning of the phase is the phase shift of the ground ( done by pressing the balance button ), then the third detector is not needed?

[Qiaozhi]

A third channel is sometimes provided in VLF detectors that can display a target ID, as this is based on the phase angle of the target, and this can be offset if there is an external ground balance control. It depends on how pedantic you are about the target ID accuracy.
In Tesoro detectors without a display (such as the Bandido) the third channel is a non-motion mode for pin-pointing. I don't know about the Bandido III variant without seeing the schematic.

[Pep_T]

Hi, I actually tried the part of the schematic that generate the negative rail for the op amp and it does not work! It generates barely -2.7V and needs a voltage multiplier to be able to generate at least -5V. With some help I found out that the attached version works, I am still using it to power a couple op amps from +5V. Diodes can be replaced with 1N4148 and the 5kHz signal for the push pull stage generated by anything you want. Measured output voltage is about -7.5V

[pito]

barely -2.7V ":415781}[/ATTACH]

These are old fashioned op amps, if you change all of them to modern ones such as MCP6022 you don't need negative voltage and have only one type of them.

This is my opinion, what another experts say ?

[pito]

A third channel is sometimes provided in VLF detectors that can display a target ID, c.

And what is the phase difference between XCLK and GCLK ?

It depends on how pedantic you are about the target ID accuracy. =

I am not convinced about accuracy of VDI, they are reliable at 50% of maximum range.
At maximum range VID is giving different numbers for the same object for each swing.

[Pep_T]

These are old fashioned op amps, if you change all of them to modern ones such as MCP6022 you don't need negative voltage and have only one type of them.

This is my opinion, what another experts say ?

While it is true that most of modern op amp works with single supply, if the input signal goes negative the op amp must be able to work with that. Dual supply poses no problems, but with singe supply an input biasing stage would be needed that this schematic does not contain

[pito]

it is that simple

[Carl-NC]

Hi, I actually tried the part of the schematic that generate the negative rail for the op amp and it does not work! It generates barely -2.7V and needs a voltage multiplier to be able to generate at least -5V. With some help I found out that the attached version works, I am still using it to power a couple op amps from +5V. Diodes can be replaced with 1N4148 and the 5kHz signal for the push pull stage generated by anything you want. Measured output voltage is about -7.5V

The charge pump inverter running from +5V will never be able to reach -5V, but it should reach -4V even with a nominal load current, and that should be enough. If it only reaches -2.7V then the load current may be too high. For that, you can try increasing the size of the caps.

[Pep_T]

Hi, I made a couple of tests and even widouth any load It did not go beyond -3V. A 1k load did not make any diffference. I should try again and see what happends increasing the size of the capacitors.

[Carl-NC]

And what is the phase difference between XCLK and GCLK ?

It looks like GCLK is fixed at about 5° beyond RCLK. That means when perfectly GB'd to ground with a loss angle of 5° (fairly average) the RCLK will be at exactly 90°. The XCLK phase is set by the Disc setting, I'd have to run a sim to see what the phase range turns out to be. It's a little curious that RCLK varies with GCLK. Normally, you want RCLK fixed and only GCLK varies with ground balance.

In the Bandido, the G channel is used for all target responses: AM, Disc, and pinpoint. It has a retune circuit so it is a first-derivative motion channel, but the retune can be disabled to make it a static non-motion channel for pinpoint. The Disc circuitry (using the X & R channels) provides a blanking signal that kills the G channel signal when the target is seen as something undesirable. Otherwise, desirable targets beep.

Modern VLF designs no longer vary the demod clocks to achieve disc as it weakens nearby target responses. Instead, the X & R channels are fixed at 0° and 90° and discrimination is done after the demods by ratiometric comparisons.

[pito]

the X & R channels are fixed at 0° and 90° and discrimination is done after the demods by ratiometric comparisons.

that what I mean in post #16

And similar story is with Delta Pulse, where they are using 7 x cd4066 ?

[Carl-NC]

And similar story is with Delta Pulse, where they are using 7 x cd4066 ?

Completely different animal.