nulling Tx and Rx fields

[MineDetector]

First of all let me say thanks for Geotech for providing all great resource on building metal detectors.

Now to the question; I am trying to build the Magnum Metal Locator and in middle of winding the coils (4B or pinpoint style). Once this is done I have to fix the position of the coil so transmitted signal cancel around the receiver. Is it possible to check this exact point by connecting the transmitter into a signal generator and the receiver into an oscilloscope? i.e., without building the rest of the circuit at this stage?

Thanks for any feedback.

[James O.]

Yep

Yep. If your also connecting the tuning caps then make sure the signal generator is at the same frequency as the resonance of the tank circuit else it wont produce much of a field. Adjust the coils for the smallest output on the recieve coil and CHECK that ferrous and non ferrous metals affect the signal in the desired way i.e increase or decrease amplitude.

Good luck.

[Max]

First of all let me say thanks for Geotech for providing all great resource on building metal detectors.

Now to the question; I am trying to build the Magnum Metal Locator and in middle of winding the coils (4B or pinpoint style). Once this is done I have to fix the position of the coil so transmitted signal cancel around the receiver. Is it possible to check this exact point by connecting the transmitter into a signal generator and the receiver into an oscilloscope? i.e., without building the rest of the circuit at this stage?

Thanks for any feedback.

Hi,
yes you can do it. Connect right capacitor on tx coil to get resonance as explained above. On rx you need another capacitor like in rx stage in the circuit and a load resistor (from 1kohm to 10kohm) to avoid oscillations at resonance frequency of rx tuned circuit. Then use the scope to get some mV peak to peak of nulling. Try this before apply the shield then again after to see if everything ok...then pot everything with epoxy.

Best regards,
Max