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Using a Ferrite Ring to Proof-Test the GB pot in a Tesoro Bandido II µMax.

ToddB64

Elite Member
Joined
Jan 30, 2006
Messages
749
Location
Georgetown, Ohio, USA
Hi All ! :tiphat:

Without addressing the word "null" in all it's various forms (noun, verb, adverb, adjective, etc., etc., I think we know that null basically means of no value, zero, non-existent. OK, so that definition is what we usually strive for when adjusting the GB control to null the Threshold "Hum", or whatever description you use to describe your metal detector's Threshold sound.

In addition, due to the level of mineralization in the ground where we decide to hunt, absolute zero Hum may not be possible. Therefore, we adjust the GB control positive or negative to achieve the lowest Hum levels possible as we raise and lower the coil typically from 6" or 8" above the ground, down to about 1" above, repeating this "bobbing" of the coil and noting whether the increase or decrease in Hum level occurs as we lowed or raised the coil and then making the needed GB control adjustments until the Threshold Hum gets as close to 'Spot-on' as possible. However, some detectorists prefer a slightly positive Ground Balance. They believe a tiny bit positive helps the machine run smoother and will work well in more conditions and soil types. I like a 'Spot-on' ground balance setting.

Having said the above, I'll get to the gist of this post. I have a ferrite ring for testing whether or not the GB Variable Resistor (or Variable Potentiometer Control, also referred to as a "POT" in electronics.) in my Tesoro Bandido II µMax control box circuit is functioning correctly. The test involves attempting to null the Threshold Hum while bobbing the coil over the ferrite ring and adjusting the GB control using the method described in the previous paragraph.

I presume a ferrite ring normally contains a much higher degree of iron dust or iron particle saturation than the average ground, and therefore is a more severe test of the GB pot. If the pot passes this test, we can be certain that it is operating correctly and will meet all the ground mineralization challenges normally encountered, at least in the Ohio parks that I hunt. :ewink:

As always, I welcome your comments.

Thanks,
ToddB64
 
ToddB64: said:
Hi All ! :tiphat:

Without addressing the word "null" in all it's various forms (noun, verb, adverb, adjective, etc., etc., I think we know that null basically means of no value, zero, non-existent. #1.. OK, so that definition is what we usually strive for when adjusting the GB control to null the Threshold "Hum", or whatever description you use to describe your metal detector's Threshold sound.

In addition, due to the level of mineralization in the ground where we decide to hunt, #2.. absolute zero Hum may not be possible. Therefore, we adjust the GB control positive or negative to achieve the lowest Hum levels possible as we raise and lower the coil typically from 6" or 8" above the ground, down to about 1" above, repeating this "bobbing" of the coil and noting whether the increase or decrease in Hum level occurs as we lowed or raised the coil #3..and then making the needed GB control adjustments until the Threshold Hum gets as close to 'Spot-on' as possible. However, some detectorists prefer a slightly positive Ground Balance. They believe a tiny bit positive helps the machine run smoother and will work well in more conditions and soil types. I like a 'Spot-on' ground balance setting.

Having said the above, I'll get to the gist of this post. #4..I have a ferrite ring for testing whether or not the GB Variable Resistor (or Variable Potentiometer Control, also referred to as a "POT" in electronics.) in my Tesoro Bandido II µMax control box circuit is functioning correctly. #5..The test involves attempting to null the Threshold Hum while bobbing the coil over the ferrite ring and adjusting the GB control using the method described in the previous paragraph.

I presume a ferrite ring normally contains a much higher degree of iron dust or iron particle saturation than the average ground, and therefore is a more severe test of the GB pot. If the pot passes this test, we can be certain that it is operating correctly and will meet all the ground mineralization challenges normally encountered, at least in the Ohio parks that I hunt. :ewink:

As always, I welcome your comments.

Thanks,
ToddB64
Todd, I'll gladly try to help by letting you know you are incorrect in your adjustment descriptions.

Readers should understand that with most detectors, you would be using an All Metal search mode with a properly-adjusted slight audio Threshold 'Hum' during the search. This would be the case using your Tesoro Bandido II µMAX if you are trying to adjust for a 'proper' Ground Balance to use in the All Metal mode.

There are some makes and models that use a Threshold audio in the motion-based Discriminate mode, but perhaps a majority today that are 'silent-search' in the motion-based Discriminate mode. Many of these detectors rely on a factory preset GB for the Disc. modes and a manual or automated Ground Balance is only done in, or for, the All Metal mode which usually also applies to the Threshold-based Pin-Point function.

Therefore, when discussing the use of a Threshold setting and making a Ground Balance adjustment, it is typically going to be done in an All Metal mode. Thus, let me explain by referring to what I numbered above:

#1.. Incorrect .. We should not try to adjust the Ground balance to 'Null' the Threshold 'Hum.' We should be adjusting the Ground Balance to cancel out or ignore the effect of mineralized ground so that we maintain a 'spot-on' or consistent audible Threshold 'Hum' from ±6" down to about 1". Ground Balance is just that, an adjustment method to 'Balance' or 'Cancel' or 'Ignore' the effects of mineralization on the EMF. That way it allows us to search while listening to the faint or slight audio 'Hum' which is referred to as the 'Threshold' of sound.

#2.. "Absolute zero 'hum' is not what we are trying to achieve. We want to hear the audio Threshold 'Hum' in order to discern slight variations in the ground mineral make-up or to better hear a weak good-target response.

#3.. When you first start any Ground Balance procedure, you are already starting with 'proper' Threshold audio with a slight 'Hum' when the search coil is held at ±6" off-the-ground. That is a 'spot-on' Threshold setting. The Ground Balance adjustment is done so that you maintain that Threshold 'Hum' when raising or lowering the search coil because the GB setting cancels any positive or negative influence on that 'proper' or 'spot-on' Threshold setting.

So we start out by adjusting a 'sport-on' Threshold and then we don't change the Threshold adjustment.

We only change the Ground Balance adjustment so that we then have a 'spot-on' GB setting in order to maintain a 'spot-on' Threshold setting. Two different settings and each has their own 'spot-on' adjustment.

#4.. The ferrite ring, or a mineralized rock, or using an asphalt parking lot or the bare dirt in your yard, can let you see if the GB control is functioning correctly. The only thing you might notice is that using a smaller test piece, such as a very mineralized rock or a ferrite ring, won't have the same effect on the whole EMF like balancing over dirt or parking lot asphalt, but instead must be presented in a direct toward-and-way motion in-line with the center-axis of the search coil.

A small intense test piece in the tighter EMF orientation to achieve a proper GB adjustment. The result can be a touchier GB adjustment, especially since that model only uses a 3¾-turn GB Pot. So the control is more of a coarse-tune rather than a fine-tune control. Additionally, you won't have any control over the Sensitivity setting in the Threshold-based All Metal mode because that model's Sensitivity is already preset for the All Metal mode. The variable Sensitivity control is only a receive-gain function for the motion-based Discriminate mode to help deal with EMI or other challenges.

So you need to adjust for a proper Threshold 'Hum' and then adjust the GB control in order to cancel ground effects on the EMF in order to maintain that proper Threshold 'Hum', and do so with a touchy variable GB pot, and in the All Metal mode.

#5.. NOPE! The 'test' of the ferrite ring or any other mineralized matter is to be able to adjust the GB to maintain the Threshold audio 'Hum' and NOT Null it out.

Keep in mind that we are talking about adjusting for a proper Threshold audio and Ground Balance for use in the All Metal search mode for peak efficiency.

Monte
 
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