A
Anonymous
Guest
What are the main contributing factors that cause this to happen. Could it be the casing material,the distantance wires or sheilds are apart.
Regards Frank Wallis
Regards Frank Wallis
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A
Anonymous
Guest
Hi Frank,
I suppose that what you mean for 'static discharge' is an electric spark in the coil winding or in the cable , or endly in the electronic unit.
If it is so, well, you probably have a shield problem in your coil or cable ...or maybe the clamping diodes and/or the dump resistor are burned and that causes the discharge to happen.
If the spark is in the cable you must use a different one with a higher/tick internal shield.
If in the winding , then again you need to change your wire or winding scheme or other factors like glue, shielding spray...etc...also the distance of the turns will be important if you use a thin shielded wire <IMG SRC="/forums/images/smile.gif" BORDER=0 ALT="
">
If the diodes/dump res. are burned you only need to find new ones and change them.
Bye,
Massimo
I suppose that what you mean for 'static discharge' is an electric spark in the coil winding or in the cable , or endly in the electronic unit.
If it is so, well, you probably have a shield problem in your coil or cable ...or maybe the clamping diodes and/or the dump resistor are burned and that causes the discharge to happen.
If the spark is in the cable you must use a different one with a higher/tick internal shield.
If in the winding , then again you need to change your wire or winding scheme or other factors like glue, shielding spray...etc...also the distance of the turns will be important if you use a thin shielded wire <IMG SRC="/forums/images/smile.gif" BORDER=0 ALT="
">If the diodes/dump res. are burned you only need to find new ones and change them.
Bye,
Massimo
A
Anonymous
Guest
Hi Massimo and Frank,
I think what Frank means is the occasional transient signal that you get from static electricity build up on the plastic coil case. This phenomena seems to occur when prospecting in dry hot climates. You never get it when searching a wet beach or on damp ground.
Plastics, unless they have a conductive filler like carbon, are very prone to static build up due to friction between the shell and dry vegetation, quartz sand grains, or other dry ground. This will eventually build up to such a potential that it sparks over to a nearby conductor, perhaps the coil shielding. If the detector operator has leather soled shoes, is damp with sweat, or has had too many tinnies, the discharge path will probably be via his body to the ground. The spark often causes a sudden loud audio response as it temporarily reacts with the electronics. However, it is a non-repeatable signal which is not confused with a target response.
Eric.
I think what Frank means is the occasional transient signal that you get from static electricity build up on the plastic coil case. This phenomena seems to occur when prospecting in dry hot climates. You never get it when searching a wet beach or on damp ground.
Plastics, unless they have a conductive filler like carbon, are very prone to static build up due to friction between the shell and dry vegetation, quartz sand grains, or other dry ground. This will eventually build up to such a potential that it sparks over to a nearby conductor, perhaps the coil shielding. If the detector operator has leather soled shoes, is damp with sweat, or has had too many tinnies, the discharge path will probably be via his body to the ground. The spark often causes a sudden loud audio response as it temporarily reacts with the electronics. However, it is a non-repeatable signal which is not confused with a target response.
Eric.
A
Anonymous
Guest
Hi Eric and Massimo
One problem when you are looking for gold is this discharge, which tends to have you swinging the coil back to see if it is a target or not,it is a problem in all coils.I just made a 14x10 and covered the outer with rubber bike tube to see if we could totally solve the problem,but the results were terrible,if you touched a small peice of grass (green)it would sound off,but small twigs did not seem to effect it so much.
I have two feelings that perhaps the sheild must not be too close to the outer case,and not to use resin or glues,to fix it in.
Regards Frank Wallis
One problem when you are looking for gold is this discharge, which tends to have you swinging the coil back to see if it is a target or not,it is a problem in all coils.I just made a 14x10 and covered the outer with rubber bike tube to see if we could totally solve the problem,but the results were terrible,if you touched a small peice of grass (green)it would sound off,but small twigs did not seem to effect it so much.
I have two feelings that perhaps the sheild must not be too close to the outer case,and not to use resin or glues,to fix it in.
Regards Frank Wallis
A
Anonymous
Guest
This discharge can be downright amazing in the way
that it occurs. It appears to need a conductive
green plant to discharge but can charge and discharge repeatedly in some long lilly type leaves. The only solution it seams is to form a
connection between the search head plastic, the
operator, power supply and the ground we walk on
or as Eric has suggested, use a material for the
coil housing that does not create static build up.
Plastic has to be close to the worst for this, try
swinging in strong dry wind, the detector can be
almost impossible to use as it then doesn't need
a highly conductive plant, poor conductors will
trigger a noise.
that it occurs. It appears to need a conductive
green plant to discharge but can charge and discharge repeatedly in some long lilly type leaves. The only solution it seams is to form a
connection between the search head plastic, the
operator, power supply and the ground we walk on
or as Eric has suggested, use a material for the
coil housing that does not create static build up.
Plastic has to be close to the worst for this, try
swinging in strong dry wind, the detector can be
almost impossible to use as it then doesn't need
a highly conductive plant, poor conductors will
trigger a noise.
A
Anonymous
Guest
Hi Robby
I have even used light smear of graphite on the surface of the coil,with tap to the sheild.
Regards Frank Wallis
I have even used light smear of graphite on the surface of the coil,with tap to the sheild.
Regards Frank Wallis
A
Anonymous
Guest
Hi Frank,
It would be interesting to see if my type of coil construction gives any improvement. In an open ring coil, there is much less surface area of plastic on which static can develop. Also, the total shielding of the coil with lead foil should, with proper grounding in the electronics, conduct any discharge away without affecting the electronics. One of the tests we do in industrial PI's (which also use this form of coil construction) is an electrostatic discharge test. If properly designed, the detector is immune to this and gives no false alarm.
Eric.
It would be interesting to see if my type of coil construction gives any improvement. In an open ring coil, there is much less surface area of plastic on which static can develop. Also, the total shielding of the coil with lead foil should, with proper grounding in the electronics, conduct any discharge away without affecting the electronics. One of the tests we do in industrial PI's (which also use this form of coil construction) is an electrostatic discharge test. If properly designed, the detector is immune to this and gives no false alarm.
Eric.
A
Anonymous
Guest
Hi Eric
The type of coils that I make are of the tube design,and that tends to not have less much surface area.I have been making some large coils 2ft and larger,and one problem has been that too much sheilding tends to make it hard to ground balance,on coils this size I have found best to use very fine 0.1mm of high resistance wire.
Regards Frank Wallis
The type of coils that I make are of the tube design,and that tends to not have less much surface area.I have been making some large coils 2ft and larger,and one problem has been that too much sheilding tends to make it hard to ground balance,on coils this size I have found best to use very fine 0.1mm of high resistance wire.
Regards Frank Wallis
A
Anonymous
Guest
Hi Frank,
Is your detector still a SD2---?
Eric.
Is your detector still a SD2---?
Eric.
A
Anonymous
Guest
Hi Eric
I have both SD2000 &2200
Regards Frank Wallis
I have both SD2000 &2200
Regards Frank Wallis
A
Anonymous
Guest
It isn't an easy thing to test. You may think you
have it beat only to go out and have it occur
just as bad. What ever it is should be fixable
but only if you can stop the discharge from
happening as it must make a rf noise when it occurs. Maybe it will forever build up to what
ever potential it takes to do a round circuit
from the coil housing thru the body, dragged
conductor to the moist depth of the plants tap
root as most of the time a dragged conductor is
skidding along leaves, a dead dry clay surface
or small bundles of twigs. I once stuck short
lengths of fishing line to the coil housing with
the thought that it would bleed any build up to
ground, didn't work.
have it beat only to go out and have it occur
just as bad. What ever it is should be fixable
but only if you can stop the discharge from
happening as it must make a rf noise when it occurs. Maybe it will forever build up to what
ever potential it takes to do a round circuit
from the coil housing thru the body, dragged
conductor to the moist depth of the plants tap
root as most of the time a dragged conductor is
skidding along leaves, a dead dry clay surface
or small bundles of twigs. I once stuck short
lengths of fishing line to the coil housing with
the thought that it would bleed any build up to
ground, didn't work.
A
Anonymous
Guest
Hi Frank,
One problem is that adding shielding also adds capacitance to the coil circuit. I found that when making large coils for the SD2200 that I had to compensate for this capacitance, otherwise the ground balancing would be affected. The extra capacitance causes an overshoot in the coil response, which I had to compensate for both in time constant and amplitude to make the ground balance good again. I used a Minelab mono coil as a reference and adjusted any new coil to have the same response shape. You need a scope and suitable test gear to do this.
Eric.
One problem is that adding shielding also adds capacitance to the coil circuit. I found that when making large coils for the SD2200 that I had to compensate for this capacitance, otherwise the ground balancing would be affected. The extra capacitance causes an overshoot in the coil response, which I had to compensate for both in time constant and amplitude to make the ground balance good again. I used a Minelab mono coil as a reference and adjusted any new coil to have the same response shape. You need a scope and suitable test gear to do this.
Eric.
A
Anonymous
Guest
Hi Eric,
I wonder if you could clarify that a bit more.
You appear to be saying that you have to increase
the damping but if so, how do you then adjust the
time constant, don't you end up with a longer
decay time after all this? Sorry if I have misunderstood.
I wonder if you could clarify that a bit more.
You appear to be saying that you have to increase
the damping but if so, how do you then adjust the
time constant, don't you end up with a longer
decay time after all this? Sorry if I have misunderstood.
A
Anonymous
Guest
Hi Eric
I have a scope,but in regards to sheilding that is what I found that you had to be so careful in regards to the amount that you applied,that task we did in the field.
Regards Frank Wallis
I have a scope,but in regards to sheilding that is what I found that you had to be so careful in regards to the amount that you applied,that task we did in the field.
Regards Frank Wallis
A
Anonymous
Guest
Did you try useing Static Guard? I use it on my truck seat, It prevents the static electricity, I don't get shocks. Spray some on the coil, It may do the trick. You probably can use Bounce also, by wipeing it on the coil. If you have a coil cover, you could put a sheet of Bounce inside. It may do the trick.
Fred
Fred
A
Anonymous
Guest
Terry Crenshaw and I sprayed a "heavy duty" anti-static fluid on the coils of his SD2200d.This gave them a condutive surface by which we bled off any potential to the ground via conductive foam at the lower coil/lower rod joint to a thin stranded wire up the rod to a connection on the control box to a chain or other condutive wire/cable draging on the ground.
We found this most usefull during dry windy days.
We found this most usefull during dry windy days.
A
Anonymous
Guest
We used heavy duty Staticide made by a US co.
acl Staticide part# 2005
acl Staticide part# 2005