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Those who use Tom Dankowski's forum will have seen this thread about a new 'VLF' machine, the Tarsacci MDT-8000:
http://www.dankowskidetectors.com/di...,152652,page=1
It's designed by Demeter Gargov, a former Fisher engineer, the CoinStrike being one of his projects.
It appears to be fundamentally a selectable single-frequency VLF machine (6.4, 9,12,18kHz), with a regular-looking DD search-coil. It has the advantage of giving greater depth than a standard single-freq VLF, it seems. This makes me conclude that it has some method of reducing the effect of the ground signal.
It's not inconceivable that it uses multi-frequency like the Fisher CZ-series, so when 9kHz is selected, it's actually (9 and 27 kHz) etc.
But reading the 'operating instructions' suggests that it is actually something different - the audio has a different sound, there's a special ground-balancing procedure. This makes me think it may be using additional sensors to determine ground signal, probably Hall sensors, though other possibilities exist.
The appearance of the coil shows that if there's anything extra inside the case, it's quite small. There's probably not any secondary transmit or receive coils.
It's also stated that the machine is 'matched' to the coil, it's not possible the swap coils. If it had a secondary sensor, this might imply the main control box is used to calibrate the way 'VLF coil' and 'secondary sensor' are processed.
It's also stated that it is more sweep-speed sensitive than regular machines.
It could be because the two sensors don't match up perfectly. That is to say, the sweet-spot of the main DD is in the exact centre of the coil, but the 'secondary' sensor is perhaps magnetically centred 7 cm to the right. So a small delay process is needed, to match up the readings from the sensors. This would also require an accelerometer/rate-gyroscope in the coil, to determine sweep direction/speed, as the left-right sweep would be processed differently to the right-left sweep.
This delay-processing would be optimised for a particular sweep-speed, hence swinging too slow or fast may give odd results.
My guess is it's got Hall sensors, probably several of them, some near the 'toe' of the TX coil, some near the 'heel'. These would be averaged to give a reading of the mid-point of the coils length.
Anyone got any thoughts, analysis, clever ideas ?
Do you reckon there's any chance of us creating anything like this ourselves ?
I read that Mr. Gargov spent many years on the design, so it's probaly not that easy.
http://www.dankowskidetectors.com/di...,152652,page=1
It's designed by Demeter Gargov, a former Fisher engineer, the CoinStrike being one of his projects.
It appears to be fundamentally a selectable single-frequency VLF machine (6.4, 9,12,18kHz), with a regular-looking DD search-coil. It has the advantage of giving greater depth than a standard single-freq VLF, it seems. This makes me conclude that it has some method of reducing the effect of the ground signal.
It's not inconceivable that it uses multi-frequency like the Fisher CZ-series, so when 9kHz is selected, it's actually (9 and 27 kHz) etc.
But reading the 'operating instructions' suggests that it is actually something different - the audio has a different sound, there's a special ground-balancing procedure. This makes me think it may be using additional sensors to determine ground signal, probably Hall sensors, though other possibilities exist.
The appearance of the coil shows that if there's anything extra inside the case, it's quite small. There's probably not any secondary transmit or receive coils.
It's also stated that the machine is 'matched' to the coil, it's not possible the swap coils. If it had a secondary sensor, this might imply the main control box is used to calibrate the way 'VLF coil' and 'secondary sensor' are processed.
It's also stated that it is more sweep-speed sensitive than regular machines.
It could be because the two sensors don't match up perfectly. That is to say, the sweet-spot of the main DD is in the exact centre of the coil, but the 'secondary' sensor is perhaps magnetically centred 7 cm to the right. So a small delay process is needed, to match up the readings from the sensors. This would also require an accelerometer/rate-gyroscope in the coil, to determine sweep direction/speed, as the left-right sweep would be processed differently to the right-left sweep.
This delay-processing would be optimised for a particular sweep-speed, hence swinging too slow or fast may give odd results.
My guess is it's got Hall sensors, probably several of them, some near the 'toe' of the TX coil, some near the 'heel'. These would be averaged to give a reading of the mid-point of the coils length.
Anyone got any thoughts, analysis, clever ideas ?
Do you reckon there's any chance of us creating anything like this ourselves ?
I read that Mr. Gargov spent many years on the design, so it's probaly not that easy.
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