Gain and Sensitivity

[Mikel]

How does the gain differ from sensitivity in the XS? I heard the output to the coil is always the same and is not adjustable? Is this true?

 

[Cody]

Gain and Sensitivity is a function of the receiver and does not increase or decrease "power" transmitted. Gain adjusts the ratio of input to output for amplification. As an example if we have a gain of 10 for an amplifier with one volt in we get 10 volts out. Sensitivity would adjust the same amplifier for how small of a signal we amplify at the gain setting. As an example with the Explorer set to max gain we will amplify the faintest signals at the gain setting. If we have a signal, just as an example, of .01 volts and the gain set to 10 then the output of the amplifier would be 10 X .01 = .1 but consider the problem of external noise that is also .01 volts. You see what happens we amplifier the noise and signal to .1 so we can miss the signal in the noise.

Gain on the Explorer is what is often called modulated. It is not linear so that from 1, 2, 3,........10 increase the gain in a linear manner. Instead if gain is set below 5 we are going to hear the insensitivity of the signal in relationship to how deep the target is in the soil. At a setting of 5 the gain is between this and amplifying all signal to a fairly intense level. So, from 6 to 10 all signals sound pretty much the same but below five a deep signal will sound faint and surface signals intense.

I set the sensitivity as high as I can get it with good stability, use good headphones, and most of the time have the gain set to 3 or 4. It is like getting use to hearing a sound in a room full of loud noise or in one with little background noise. Once our ears get use to a gain of 3 or 4 it sound very normal. A primary reason I do is due to tinnitus which is ringing in the ear and loud sound can aggravate the condition. One thing I have noticed is when gain is at a high level the pinpoint report is more clear on ultra deep targets.

 

[Mikel]

So the sensitivity sets the size or amount of signal the gain amplifies?

 

[Travis]

OK, here's how I understand it, now I am no expert but I think I understand this pretty well. Cody is good, I will just try and rephrase his answer.

Gain:
It is a "signal volume boost". At a lower setting, shallow targets sound louder in volume and deep targets sound lower in volume. At a higher setting, it "boosts" or amplifies the deeper target sound so you can hear it easier, but is harder to tell the depth from the sound alone then. I use a higher gain setting. This is NOT related to the tone or pitch, but ONLY the volume of the target sound.

Sensitivity:
This is a setting that you set to tell the detector how sensitive you want it to be. The higher you set it, the more it will be sensitive to any possible targets (within the bounds of your discrim. settings). The lower you set it, it will not be as sensitive to very small or weak targets.

Hope this helps.
HH
Travis

 

[Chris(SoCenWI)]

Cody's answer was short, sweet, and accurate. Very nice job Cody.

Sensitivity (We Think?!) sets the level at which the signal must exceed to get processed, discriminated, and eventually amplified by the gain circuit. Using Cody's example above, with sensitivity at Max - real manual max - not auto, all signals would get amplified, so a teeny .01 volt signal would be acted upon and amplified.

Most places there is too much ambient electrical noise for us to run at this high of a sensitivity. Remember that your coil acts much like a radio's attennae and will pick up signals from the air. When you hear your explorer going crazy when you are not moving the coil it is because it is processing all the signals it is picking up through the air.

Noise canceling can help, but often the electrical noise from powerlines covers alot of frequencies and changing the recieve frequencies slightly does little to help. In this case the only solution is to start turning down the sensitivity. This basically means we are telling the explorer not to process any signal below a certain voltage because we think it is likely that these signals are caused by noise, not a target. Thus maybe the smallest voltage is now .5 volts that will get processed.

The down side is that real deep and faint targets will also be missed.

Chris