Minelab Metal / Gold detector modifications SD2000 SD2100 SD2100E SD2200 SD2200V2 GP Extreme GP3000 GP3500 GPX4000 GPX4500 Detectormods is part of Link Technologies.
What are the advantages of a Modified Minelab Detector? Many people would ask this question and i will explain some of the rational behind the science.
Ever since the first Minelab detectors, such as the SD2000 came onto the prospecting scene many people complain about noise and false signals. All these detectors have a very wide bandwidth receiver preamplifier and this is in order to make the detectors better at finding very small Gold. This wide bandwidth approach also makes the detector susceptible to man made interference and natural interference such as lightning strikes from storms many hundreds of miles away. Minelab have used a filter that can be classed as a high impedance in an attempt to stop this type of interference, we found a better approach in using low Q low impedance filters that start operating just above the pass band of wanted signals. Instead of trying to stop these signals our technique absorbs these interfering signals and has a negligible effect in the range of 1hz to 15khz. We use material that can operate correctly with unipolar pulses and need no reset mechanism when compared to the standard ferrite inside the metal detectors.
Most users have noted that these pulse induction detectors are relatively noisy in mineralized soil, the jitter, groans and growls easily mask the signals from Gold Nuggets. It is imperative that we reduce or eliminate this type of noise from the system. I noticed that the filter band pass response was not sharp enough to reduce this type of noise so we remodeled the filter response to that with a greater low frequency cut off to reduce the noise.
Small Gold and short time signature Nuggets.
I do not want to get too technical here but it is important to understand the nature of the ground and gold to be able to design a properly working and optimized metal detector. When a pulse induction metal detector energizes the coil it emits an electromagnetic field into the ground and above the coil. this field excites the ground minerals as well as gold nuggets and many other metals. When the energy from the detector ceases to flow into the coil, the energy still stored in the coil collapses, this energy wants to go somewhere and it is converted into a high voltage pulse. This is clamped inside the detector by a FET used as a resistive element across a 200 volt rated capacitor, a voltage feedback circuit controlled by a comparator clamps the voltage to around 185 volts.This high voltage pulse is nuisance value, it takes time to get rid of it. It also masks the initial signal being sent back to the detector from the ground and any metal targets.When current flows into the coil it generates a field that creates a current flow into any conductive object it connects with, when the flow is stopped the round and metal targets give of the current as their own field that is picked up by the coil.These fields are very small and die off very fast, that is why it is a fine balance of waiting for the back EMF pulse to dissipate and get the metal detectors receiver turned on as fast as possible to capture the signal from the target before it dies off. There is a lot going on at this point because you have target signals mixed with ground signals and they all need to separated or the detector will not know whats what.
Minelabs patented ground subtraction is critical to removing the ground signal from masking target signals, the system can be looked at as gold is one vector and ground is another, by some maths it can be determined to some degree what is ground and what is metal.
Im probably getting a little carried away with all of the above but it comes down to this, Fast Coils, Correct Coil Damping, Very low noise Receivers, Wide Bandwidth but correctly filtered, Low Capacitance in relation to the Receiver input, Very good and accurate ground balance circuitry. Overall it is the quieter the detector the more Gold you will find.
There are some prospectors that turn everything up flat out and only find surface bits of Gold, the smarter ones get the detector as quiet as possible and they find the larger deeper ones.
Modded detectors are so much quieter, that is why they pull the largest lumps at depth.
