Capacitance and Resistance in epee wiring

[jjefferies]

Just rewired an older blade. Wanted to assure that the cup with the contacts didn't rotate ( a problem that I've noted previously creating problems) so I put a bit of loctite on the bottom of the cup before I inserted it. That appears to have gone correctly but as a caution that it wasn't crimping against anything I measured the resistance with a digital multi-meter. Found the resistance between wires and between the wires and the blade to be in the meg-ohms but still measurable. Further, resistance would decrease as I put on a new coating of glue (crazy glue). So I thought that the still wet glue was causing the observable resistance and so I continued as usual. But after the glue has hardened I still find a finite resistance where it should be open. Moreover I find that the resistance will begin in the 10 megohm region and then continue to increase like it was a capacitor. So any suggestions? votes on it being:
1. a crimped wire or the wire being pressed against the metal somewhere?
2. use of the loctite on the bottom of the cup?
3. some weirdness having to do with the use of superglue??
4. Anything else?

[Mergs]

Well, one of the problems I see is that the required resistance of the weapon is supposed to be 2 ohms max, so if you are seeing megohms resistance, you have a problem. The capacitance effect is probably related to the use of CA. I would do away with the CA entirely and use compression to ensure a good connection, ie the pommel nut.

[migopod]

Well, one of the problems I see is that the required resistance of the weapon is supposed to be 2 ohms max, so if you are seeing megohms resistance, you have a problem. The capacitance effect is probably related to the use of CA. I would do away with the CA entirely and use compression to ensure a good connection, ie the pommel nut.

If I'm correctly understanding the OP it's in the megaohms when the circuit is open rather than infinite resistance. In theory couldn't the contacts inside the tip, or maybe some dielectric effect of the CA on the wires mimic a capacitor? Curious as well if the effect is significantly diminished when the glue completely cures.

Personally I don't think I've put nice enough ohm meter on an epee to distinguish between infinite and megaohms.

[K O'N]

Just rewired an older blade. Wanted to assure that the cup with the contacts didn't rotate ( a problem that I've noted previously creating problems) so I put a bit of loctite on the bottom of the cup before I inserted it. That appears to have gone correctly but as a caution that it wasn't crimping against anything I measured the resistance with a digital multi-meter. Found the resistance between wires and between the wires and the blade to be in the meg-ohms but still measurable. Further, resistance would decrease as I put on a new coating of glue (crazy glue). So I thought that the still wet glue was causing the observable resistance and so I continued as usual. But after the glue has hardened I still find a finite resistance where it should be open. Moreover I find that the resistance will begin in the 10 megohm region and then continue to increase like it was a capacitor. So any suggestions? votes on it being:
1. a crimped wire or the wire being pressed against the metal somewhere?
2. use of the loctite on the bottom of the cup?
3. some weirdness having to do with the use of superglue??
4. Anything else?

What kind of wires are you using? If they're single insulation you are likely seeing some connection through the wire to the blade, then to the other wire. Measure A and B to the blade individually, I bet you get the same thing or that one of them is actually making contact and grounding. If neither is grounding you're fine, just put it together and fence with it. I don't think 10^6 ohms will show up on any box as grounding out.

K O'N

[brtech]

A thought:

How are you measuring: in particular, are you holding the meter leads to the wires with your hands?

If you are, the meter is reading your body resistance.

I wouldn't worry about 10 megohms.

[LordShout]

I had a similar issue last week, turned out to be the resistance of my hand. Check your procedure, if it still doesn't disappear maybe the parallel wires are acting as a cap. Anyone know the dielectric constant of superglue?

[migopod]

I had a similar issue last week, turned out to be the resistance of my hand. Check your procedure, if it still doesn't disappear maybe the parallel wires are acting as a cap. Anyone know the dielectric constant of superglue?

Link

Cured: @10MHz 3.3
@1Kc 5.4

[jjefferies]

Perhaps I wasn't explicit enough but not sure what Mergs means by CA? Perhaps loctite? But the resistance is between the two wires and then between each wire and the blade. And I'm not measuring my own skin's resistance. This is without human touch. The phenomena is the same wire a to blade, wire b to blade, wire a to wire b. Multi-meter shows a starting resistance of around 8 1/2 meg ohms which steadily increses by about .01 megohm per second and continues for as long as I cared to sit there and watch. at last measure had gotten to 25 megohms. One check was of the multi-meter, a FLuke 75 digital. Old but very reliable. On other weapons wired using the same crazy glue it shows infinite resistnace, i.e. open.

My next choice is to see if a scoring machine will accept the blade as is or if I will need to re-wire it again. I am using french epee wire, red in color if that clues anyone. Has a double winding of cotton insulation. The original issue was that the prior plastic contact holder (plug) was the variety that has a square recess to take the one time popular square contact piece (a German experiment?). I use Estoc tips and the tips rotate and the contact spring's end point can sometime be oriented so it doesn't make a proper contact unless it has just the right amount of travel and the square socket of the contact block was interfering. At this point my best guess is that the loctite is creating some sort of dielectric effect resulting in a small capacitance. Oh well best laid plans .......

J.

[VorpalCat]

not sure what Mergs means by CA? Perhaps loctite?

CA = cyanoacrylate = generic name for SuperGlue, Krazy Glue, Dermabond etc.

[migopod]

Perhaps I wasn't explicit enough but not sure what Mergs means by CA? Perhaps loctite? But the resistance is between the two wires and then between each wire and the blade. And I'm not measuring my own skin's resistance. This is without human touch. The phenomena is the same wire a to blade, wire b to blade, wire a to wire b. Multi-meter shows a starting resistance of around 8 1/2 meg ohms which steadily increses by about .01 megohm per second and continues for as long as I cared to sit there and watch. at last measure had gotten to 25 megohms. One check was of the multi-meter, a FLuke 75 digital. Old but very reliable. On other weapons wired using the same crazy glue it shows infinite resistnace, i.e. open.

My next choice is to see if a scoring machine will accept the blade as is or if I will need to re-wire it again. I am using french epee wire, red in color if that clues anyone. Has a double winding of cotton insulation. The original issue was that the prior plastic contact holder (plug) was the variety that has a square recess to take the one time popular square contact piece (a German experiment?). I use Estoc tips and the tips rotate and the contact spring's end point can sometime be oriented so it doesn't make a proper contact unless it has just the right amount of travel and the square socket of the contact block was interfering. At this point my best guess is that the loctite is creating some sort of dielectric effect resulting in a small capacitance. Oh well best laid plans .......

J.

If you short the wires does the resistance return to its initial state?

[jjefferies]

If you short the wires does the resistance return to its initial state?

If you leave the wires connected to the multi-meter it will eventually read infinite or "OL". If you short the wires the resistance will drop down to 30 megohm region and then begin increasing in resistance. Looks like capacitance to me.
J.

[LordShout]

Add a 9volt to the circuit and see if it reads infinite. For funsies you should find out how many pF's it is.

[jjefferies]

I finally decided that the whole thing needed re-doing and am using the blade for practice with my coach. Something really weird was going on.