Vallon VMH3CS Mine Detector

[Qiaozhi]

Hi All,

I have just obtained a Vallon VMH3CS mine detector and am surprised at how good the performance is. I've not done any detailed tests as yet, but it will detect coins at great distances in air and a 0.3gm gold nugget at 2-3 inches. This is without ground compensation. With compensation switched in (mineralisation on switch) it will cancel a substantial piece of Australian ironstone. The machine is fantastically rugged and runs off three D size batteries, so it feels a bit heavy, but is reasonably well balanced. The search coil measures 1.5mH and is 3 ohms resistance. TX pulses are bipolar and 50uS wide. It is not immediately apparent how such narrow pulses are effective using a coil of 1.5mH.

I have been off the forum for quite a long time and would be interested to know if anyone else has experience with this detector. I shall take it to the local beach next week and see how it performs there.

Eric

Wow! - that's interesting. ..... a 1.5mH coil with a 50us pulse width, but still able to detect a small gold nugget.
Did you measure the TX pulse rate?

[KingJL]

Hi All,

I have just obtained a Vallon VMH3CS mine detector and am surprised at how good the performance is. I've not done any detailed tests as yet, but it will detect coins at great distances in air and a 0.3gm gold nugget at 2-3 inches. This is without ground compensation. With compensation switched in (mineralisation on switch) it will cancel a substantial piece of Australian ironstone. The machine is fantastically rugged and runs off three D size batteries, so it feels a bit heavy, but is reasonably well balanced. The search coil measures 1.5mH and is 3 ohms resistance. TX pulses are bipolar and 50uS wide. It is not immediately apparent how such narrow pulses are effective using a coil of 1.5mH.

I have been off the forum for quite a long time and would be interested to know if anyone else has experience with this detector. I shall take it to the local beach next week and see how it performs there.

Eric

Eric,
I am extremely interested in some of the performance specs of this one. I have been working on a design that the TX is based on the Fisher Impulse. The RX preamp has just enough gain (G=32 - 64) to supply the most sensitivity and dynamic range to give a 18 bit ADC the senitivity of a 24 bit while not overloading on strong signals . Further DSP processing will be done by a FPGA... 9 samples per tx cycle. 1 for envirionmental cancellation, 8 channels cic innput filtering, 8 channels ground/mineralization filter for cancellation, 8 channel equaliztion filter. I am playing around with different timing placements of the 8 filtered channels to find out how to extract the mot information. I chose the FPGA route because all that filtering, TX control, and sample control can be done concurrently in parrallel. I was going to start with 4Khz bi-polar w/ 50 sec pw. The 1.5 mh coil sounds intriguing as I am working with ~300 uh. I have the TX/RX and the 18 bit ADC boards desgned and built. Some of the FPGA code is in design stage. The real FPGA (Spartan 6 LX25) will be obtained in the very near future.

I only detailed the above to illustrate why my interest in this detecor is high. I do not want this thread to morph into a discussion of my detector, but remain about the Vallon VMH3CS detector. If there is really any interest in what I am doing, I will start another thread. KEEP THE INFO COMING!!

[Ferric Toes]

Hi All,

I have just obtained a Vallon VMH3CS mine detector and am surprised at how good the performance is. I've not done any detailed tests as yet, but it will detect coins at great distances in air and a 0.3gm gold nugget at 2-3 inches. This is without ground compensation. With compensation switched in (mineralisation on switch) it will cancel a substantial piece of Australian ironstone. The machine is fantastically rugged and runs off three D size batteries, so it feels a bit heavy, but is reasonably well balanced. The search coil measures 1.5mH and is 3 ohms resistance. TX pulses are bipolar and 50uS wide. It is not immediately apparent how such narrow pulses are effective using a coil of 1.5mH.

I have been off the forum for quite a long time and would be interested to know if anyone else has experience with this detector. I shall take it to the local beach next week and see how it performs there.

Eric