Have you figured out that the T2 has 2 levels of zero discrimination?
Posted by: Mike Hillis
Date: June 25, 2006
This is important to understanding the T2.
Nearly all machines show the iron range as the very first conductive range on the discriminatory scale. Zero discrimination is acceptance of the iron range. There are machines with various degrees of iron acceptance, but the end result is the same; iron acceptance.
On the T2, the iron discriminatory range is 10-40. So a setting of 10 on the T2 is the same as a zero discriminatory setting we are familiar with on all other machines. This is the first zero discrimination level.
Unique to the T2 is the ability to go below iron into the mineral range, which is the 0-9 discriminatory settings. This can be technically considered to be a sub-zero disc range that is totally wide open and very susceptible to outside electrical effects as well as the internal noise of the T2 circuitry itself. This is the second zero discriminatory range. A discrimination setting of 0 on the T2 opens the T2 to receive any and all signals, including it's own circuitry noise. Once you understand this it becomes much easier to set up a stable T2 as regards to electrical interference.
This is how I am achieving stable setups:
With the coil held flat and unmoving on the ground, I select my primary tone id/target processing mode, then turn my sensitivity and discrimination settings both to zero.
I begin raising my sens setting until I start to just hear noise. I find that in my areas that it doesn't take much, usually somewhere around a sens setting of 15-25 before I start picking up electrical interference noise. I adjust my sens setting down a number or two so that the noise is barely coming through and at this point I run through the frequency selections to find the one that works best. I have found that doing the freq check at this level ensures that I am choosing the best one because I'm not overpowering the circuit, which in turn, lets me really hear which one works the best. If you can't tell as you cycle through them, then your sens level it too high and you need to back it down another number.
Once I've selected the quietest frequency, then I raise my discrimination setting to 10 (full iron acceptance or zero discrimination). Now I raise my sensitivity settings until I hear noise again and then back off a number or two until its quiet. I have now set my machine stable as far as electrical interference is concerned.
This easily lets me raise my sensitivity up into the high 70s, low 80's with no noise from electrical interference. Now, if the ground will let me, I can raise my disc up to around 25 and increase my sensitivity into the 90s and still remain stable. Thats IF the ground will let me.
The T2 is so sensitive to small and tiny targets (it is a gold machine after all) that the 'small signal' ground responses may force you to lower your sensitivity lower than required by electrical interference.
Switching to All metal mode, start with sens and hum level both at 0. Then raise the sens until you hear noise. Once you hear noise, raise your hum level until it runs steady and covers the noise. Then raise your sens level again until you hear noise. Then again raise your hum level until it 'hums' steady. I do this until I reach a hum level that I choose not to go beyond. For me, I typically stop when I reach a hum level of +3, which so far allow me to achieve higher sensitivity levels as regards to electrical interference. Then the ground always has the final say as to if I can keep it that high or not.
Remember. Electrical interference is adjusted to with a motionless coil. Ground interference is checked with coil in motion. If your detector is quiet when it is held still, you are not hearing electrical interference.
Hope this helps someone.
HH
Mike
