The comments about ground balance and noise balance are interesting so I thought I would add some input. Let me provide an illustration so clarify the differences between ground balance and noise cancel that may help. (This is a rough original of some material that will be including in my book on detectors using several of the major detectors as examples. The trick is going to be to force myself to complete the book Anyhow, you see the general way it will be presented as operating tips and tech information with about four major sections, basic and advanced, application, then basic and advanced technical theory for electronics at the science applies to metal detectors in general.)
We can think of the signal from the detector with the illustration of a runner tied to the starting line with a bungee cord. The runner has a starting point and runs away at a specific pace, reaches the maximum limits of stress of the cord and is pulled back to the starting line. (The electromagnetic field of the coil expands outward from the coil and when it reaches a maximum distance then collapses back to the coil. (The coil is the starting line and the field is the runner. The oscillator or generator in the electronics is used as a 9 reference point but the above illustration will work for now.)
Assume we are going to take measurement in two ways by which we use TIME and DISTANCE. If we use distance from the starting point then we can divide the distance into feet so that 5 feet from the starting line is 5 degrees, 90 feet is ninety and so on up to 180 feet for 180 degree. We can also use the term PHASE ANGLE for degree so we have phase angles of 5, 90, and 180 in this analogy. When we say a detector is FREQUENCY DOMAIN we are saying that the design is going to have a platform that is best explained in FREQUENCY DOMAIN as illustrated above. (We cannot purely separate frequency domain and time domain due to how they are related as both types have common applications but the implementation of the technology is considerable different in some area.)
Ground balance in FREQUENCY DOMAIN is based on the phase angle of soil minerals using PURE FERRITE as the reference. The soil in most areas is one big conducting target, and is measured, then rejected. This is like the runner on the bungee and we ignore anything that happens in the first couple of feet as he runs toward 180 feet. In other words we discriminate by TUNING OUT the soil minerals and do so with phase angles. It is obvious we can do this manually or with an automatic circuit.
Now assume we are going to take measurement using TIME instead of phase angle. We clock our runner from the starting point and make the time from 0 to 180 seconds. Now instead of phase angle we are interested in time increments. We can DISCRIMINATE but do so based on time so we ignore events that happen within the first couple of seconds which again is a form of discrimination. Since the soil minerals are one big target we can ignore any of them that fall within a specific time frame. We know that the soil will always fall within a specific time frame. If we consider a runner that can make the round trip 3000 times in a second then we see that we would need to divide the time in increments that are less than a second and each round trip represents the FREQUENCY of operation per second.
Time Domain and Frequency Domain are the fundamental operation of all hobby detectors. The Explorer operates with technology based on pulsed time domain. We can easily visualize that the Explorer rejects soil minerals based on time domain measurements. The actual implementation uses current data, what is going on at that instant in time, historical data which is what just happened, and predicts future soil data and the microprocessor uses this data to pretty much eliminate soil minerals.
NOISE CANCEL is in some ways related in that it interferes with our measurements in both frequency and time domain. However, there appears to be a lot of confusion by someone at Minelab that suggest the coil be noise canceled at waist height.
If we use the Edit accept function with a clear screen and hold the search head in free air we will see noise injected into the coil and dots start to appear on the screen. If we turn in a circle we will find that when we are pointed towards a transformer or other source of external noise we have more noise injected. If we lower the coil to the soil we will see a very different pattern of injection for noise. Movement of the coil is immaterial if the coil is in the air other than the directional properties that change if we are pointed at a noise source. In other words we can hold the coil in the air and wiggle it with no serious problem to noise cancel.
When the coil is resting on the soil we need to keep the coil still simple because the detector is motion based and we don
We can think of the signal from the detector with the illustration of a runner tied to the starting line with a bungee cord. The runner has a starting point and runs away at a specific pace, reaches the maximum limits of stress of the cord and is pulled back to the starting line. (The electromagnetic field of the coil expands outward from the coil and when it reaches a maximum distance then collapses back to the coil. (The coil is the starting line and the field is the runner. The oscillator or generator in the electronics is used as a 9 reference point but the above illustration will work for now.)
Assume we are going to take measurement in two ways by which we use TIME and DISTANCE. If we use distance from the starting point then we can divide the distance into feet so that 5 feet from the starting line is 5 degrees, 90 feet is ninety and so on up to 180 feet for 180 degree. We can also use the term PHASE ANGLE for degree so we have phase angles of 5, 90, and 180 in this analogy. When we say a detector is FREQUENCY DOMAIN we are saying that the design is going to have a platform that is best explained in FREQUENCY DOMAIN as illustrated above. (We cannot purely separate frequency domain and time domain due to how they are related as both types have common applications but the implementation of the technology is considerable different in some area.)
Ground balance in FREQUENCY DOMAIN is based on the phase angle of soil minerals using PURE FERRITE as the reference. The soil in most areas is one big conducting target, and is measured, then rejected. This is like the runner on the bungee and we ignore anything that happens in the first couple of feet as he runs toward 180 feet. In other words we discriminate by TUNING OUT the soil minerals and do so with phase angles. It is obvious we can do this manually or with an automatic circuit.
Now assume we are going to take measurement using TIME instead of phase angle. We clock our runner from the starting point and make the time from 0 to 180 seconds. Now instead of phase angle we are interested in time increments. We can DISCRIMINATE but do so based on time so we ignore events that happen within the first couple of seconds which again is a form of discrimination. Since the soil minerals are one big target we can ignore any of them that fall within a specific time frame. We know that the soil will always fall within a specific time frame. If we consider a runner that can make the round trip 3000 times in a second then we see that we would need to divide the time in increments that are less than a second and each round trip represents the FREQUENCY of operation per second.
Time Domain and Frequency Domain are the fundamental operation of all hobby detectors. The Explorer operates with technology based on pulsed time domain. We can easily visualize that the Explorer rejects soil minerals based on time domain measurements. The actual implementation uses current data, what is going on at that instant in time, historical data which is what just happened, and predicts future soil data and the microprocessor uses this data to pretty much eliminate soil minerals.
NOISE CANCEL is in some ways related in that it interferes with our measurements in both frequency and time domain. However, there appears to be a lot of confusion by someone at Minelab that suggest the coil be noise canceled at waist height.
If we use the Edit accept function with a clear screen and hold the search head in free air we will see noise injected into the coil and dots start to appear on the screen. If we turn in a circle we will find that when we are pointed towards a transformer or other source of external noise we have more noise injected. If we lower the coil to the soil we will see a very different pattern of injection for noise. Movement of the coil is immaterial if the coil is in the air other than the directional properties that change if we are pointed at a noise source. In other words we can hold the coil in the air and wiggle it with no serious problem to noise cancel.
When the coil is resting on the soil we need to keep the coil still simple because the detector is motion based and we don