Resistance and Epee Testing

[sah62]

I'm testing an epee by measuring resistance across the two wired plugs of the body cord connector. Tip extended (no contact): 0 ohms. Tip depressed (circuit complete): fluctuates widely with numbers that cause my meter to read into the millions of ohms. I expected a nice, steady reading for a weapon that's functioning normally. What does this fluctuation with high resistance readings imply? This weapon is newly re-wired with new Uhlmann wire and a Leon Paul tip.

[Mergs]

Scott,

Even though it is rewired, it may be that there is some corrosion or an intermittent short in the way you are hooking up the wire to the ohm meter. Also, if you are using german wires, make sure you have scraped off the varnish from the wire. Are you going to be at VAF tonight? If so I can take a look at it there.

Regards - Michael

[neevel]

Well, first off, for the non-depressed state do you really mean 0 ohms, or infinite (i.e., open circuit)? A reading of 0 ohms means a perfectly closed circuit, which is exactly the opposite of what you're supposed to have with the tip up. I'll proceed for now assuming you just meant that the meter showed an open circuit.

As for the reading fluctuating, that means you've got an intermittent contact somewhere. Possible causes:

-- The contact spring is bent over a bit, or is only just barely long enough, so that it's not making a good closure across the wire contacts. Straighten the spring and lenghten a tad. You said you used an Uhlmann wire and a Leon Paul tip-- I don't have any direct experience with the Leon Paul epee points, so I don't know if they're compatible with Uhlmann wires or not. If the LP point is designed to have the contacts sit higher up in the barrel than the Uhlmann wire provides for, the contact spring may not reach.

-- Did you strip off the varnish from the Uhlmann wire? Uhlmann wires have a thin coating of varnish beneath the insulating cloth-- if you don't remove it you will get high resistance. Use a bit of fine sandpaper on the stripped end of the wire.

-- The contacts and/or the end of the spring have some dirt or corrosion on them that's acting as an insulator. Clean the point out (plastic-safe contact cleaner or alcohol and Q-tips), gently scrape the wire contacts with a small screwdriver, and sand the end of the contact spring on some fine-grit sandpaper or emery paper.

-- The contact nuts at the socket might be loose or dirty. Tighten and clean them if necessary.

-- Check to make sure the wires aren't crushed beneath the grip or socket-bracket and guard.

-- Lastly, the wire managed to get broken somewhere in the wiring process, such as when you tightened the barrel (it's good idea to only feed a short length of the wire through first, tighten the barrel, and then pull the wire though- that way you only risk breaking the wire near the end).

-Dave

[sah62]

Mergs -- I won't be at the club until Friday for free fencing. I'll bring the weapon along in case you're there.

Yes, I took care of the varnish. I've also tried different tips to see if they make a difference. Nope, no difference.

The meter is indeed reading 0 ohms; maybe that's just the way this meter reflects an open circuit -- I don't know. The wire isn't broken as I run the wire only after tightening the barrel, but I can check under the grip again. Everything is nice and tight at the socket, too.

I'll check the situation at the contacts again, maybe something got screwed up in there when I set the point. It eyeballs OK, but I can't see what's going on when the contact spring sits on the contacts.

Thanks for the ideas...

[DHCJr]

Some digitals do say 0, but they usually have a small E or other indicator of Error or Open. That is one of the problems with digital meters.

One other problem with digitals is they were designed for electronic circuits, not mechanical circuits. Unless you have a very good (Expensive), it may not be fast enough to show an accurate reading.

You can get an analog that will be accurate enough (X x 1, center around 5 ohms for around $20 to $25.

All the suggestions, I saw are good. Another check is to use your tip screwdriver to short out the 2 contacts and see what the reading is.

I have both digital and analog meters, but when I am doing serious work outside the machine, I always use analog. Everything outside the machine are mechanical connections and switches.

Inside the new machines, I mostly use digital.

[oiuyt]

While we're discussing your meter, what does it read when the ends of the leads aren't connected to anything (ie you're holding them apart in the air)?

-B :)

[sah62]

While we're discussing your meter, what does it read when the ends of the leads aren't connected to anything (ie you're holding them apart in the air)?

0 ohms

[DHCJr]

I am going to ask you to look at the whole screen, not just the numbers. Put the leads together you should get 0 and you have stated when you hold them apart you also get 0.

Now is there any thing that changes on the screen, especially added when you go from connecting them together to apart. This will be your "Error" indicator or you might call it "Out of Range" or "Open".

That is how you will tell 0 from infinity.

[sah62]

The meter reads "0.L", and the "M" for the millions scale is present when the leads aren't touching anything. After reading the manual again (when all else fails... ) I found that this is the "out of range" indicator. OK, this makes sense.

I think I also managed to get past the problem tonight, which looks like it was an inconsistent contact area between the contact spring and the contacts. After spending some time to make sure that both were nice and flat the weapon is testing properly.

Interestingly, Mergs and I tested the weapon with an analog meter on Friday and it looked fine. When used on the strip, though, it was only registering touches intermittently.

Thanks for all the tips!

[neevel]

If the contact spring is a tad uneven, then the epee may register just fine when you push the button down straight-on (as people tend to do when testing) but not when it gets pushed in only from the edge of the tip, since the tip will tilt over a little as it depresses and cause the end of the spring to not touch both contacts. It's a good idea to check an epee point by pushing it down from a few spots around the edge of the tip as well as dead-on (and remind referees about this when you want them to check your epee during a bout).

-Dave