electric fence

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just the cowboy said:
It was explained if the DC contracted your muscles, you could not let go. If AC contracted your muscles they would open in the next half of the cycle. I was also told that is why AC will throw you across the room. Your muscles contract and expand in one cycle faster than we can make them do it. More voltage more push....
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That's not true at all. AC will lock you up just as much as DC if you have a firm grip on a tool or wire. There is no "push" and there is no "more push" with more voltage there is just more pain. A 120V makes you jump a 277V shock will send you across the room because of the violent reaction you have from feeling like you just got kicked by a horse square in the chest with both feet.
 
just the cowboy said:
For testing a fence just grab a piece of grass and wet it, then lay it on the fence at the tip of the grass and slide it slowly up the wire at some point you will just start to feel the shock.
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My dog once helped me with the testing. I was the macho teenager holding on to the fence with my right hand. The poor dog wandered up to sniff my left hand. Wet grass. I had boots. He didn't.
 
I used to test my electric fences by placing a metal rod against the steel post and slid it towards the hot wire. At some point less than 1", you get a spark. You can judge the strength based on the gap at which sparking commenced. I've seen people use the piece of grass method, but other variables (such as footwear) makes the results at best a go / no-go check. And may hurt like he77.
 
I REALLY prefer using an actual electric fence tester, rather than my body parts. Did that too many times as a teenager on the farm.
 
ptonsparky said:
On a more somber note a classmate of my granddaughter worked on computers. A laptop capacitor killed him. I would not recommend discharging any cap via the body parts.
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I have done work on my tube guitar amps. Filter caps can stay lethally energized for a long time after power is disconnected, so I made a discharge probe from a wirewound resistor. Sorry about your granddaughter's friend.
 
ActionDave said:
... AC will lock you up just as much as DC ...
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If I recall correctly, 60-Hz AC is about twice as effective as DC, 400-Hz AC is about equally effective as DC, and increasing frequencies are decreasingly effective.
(I was unable to find the original paper in which I read that; what I do recall is that it was published in the 1940s or 1950s. and the graph of biological effect vs frequency looks a little like a bathtub.)

Here's an online reference that suggests some of the same effect with different ratios for different effects: http://www.highvoltageconnection.com/articles/ElectricShockQuestions.htm
What's slightly disturbing is that 60 Hz seems to be the worst possible frequency available, producing the most effect with the least current.
 
Besoeker said:
My dog once helped me with the testing. I was the macho teenager holding on to the fence with my right hand. The poor dog wandered up to sniff my left hand. Wet grass. I had boots. He didn't.
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When I was a kid, my friends and I used to know a police officer that would come by and shoot the bull with us. If a couple of people grabbed hands, and the first person grabbed his car radio antenna, when the radio mic was keyed, the last person in the chain would get shocked. Or at least that was the claim.

I never had the nerve to try it.
 
drcampbell said:
If I recall correctly, 60-Hz AC is about twice as effective as DC, 400-Hz AC is about equally effective as DC, and increasing frequencies are decreasingly effective.
(I was unable to find the original paper in which I read that; what I do recall is that it was published in the 1940s or 1950s. and the graph of biological effect vs frequency looks a little like a bathtub.)

Here's an online reference that suggests some of the same effect with different ratios for different effects: http://www.highvoltageconnection.com/articles/ElectricShockQuestions.htm
What's slightly disturbing is that 60 Hz seems to be the worst possible frequency available, producing the most effect with the least current.
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IIRC 60 Hz was chosen because if you went much less you may notice strobe effect on lamps, yet other parts of the world settled on 50Hz.
 
For testing, all the fencing brands sell a digital fence tester that will give a voltage readout. They're quite cheap. But they don't work on the older chargers like the "weed burner" types. With any kind of charger a pair of pliers with decent insulation on the handles make a good tester. You just hold the joint of the pliers against a T-post and then get the tip close to the wire. With a little practice you can tell if the voltage is sufficient by how loud the arc pops.
 
Clodbuster said:
For testing, all the fencing brands sell a digital fence tester that will give a voltage readout. They're quite cheap. But they don't work on the older chargers like the "weed burner" types. With any kind of charger a pair of pliers with decent insulation on the handles make a good tester. You just hold the joint of the pliers against a T-post and then get the tip close to the wire. With a little practice you can tell if the voltage is sufficient by how loud the arc pops.
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Tester.jpg
 
Your non contact voltgage testers you use for under 600 volts works well on electric fences also, don't need to get all that close to get a signal either. Won't tell you what the voltage is, but will tell you if fence is hot or not.
 
steve66 said:
I'm not sure where you heard that, or if its true.

But I have heard AC current is worse at making a persons muscles contract in such a way that they can't control it.

I'm really not sure if that's true either. At any rate, I've always heard its safer to test an electric fence with the back of your hand, and not the palm, because the current could make your hand close around the wire, and you may not be able to let go.

Personally, I've always thought there has to be a better way to test an electric fence.
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There is! You make your little brother test it!:rotflmao:
 
electric fence

what voltage does a electric fence operate at ? ( output )
 
domnic said:
what voltage does a electric fence operate at ? ( output )
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They vary in labeled voltage. Mostly you select by the length of fencing you want to energize and the stock you want to confine - some livestock need a stronger zap than others. Due both to pain tolerance and to stupidity. So the ratings are geared towards those details.

I keep cattle that are reasonably well fence-trained in mine. It is powered off a deep cell battery which lasts about 2 weeks. In good conditions it will maintain 10-11kV line-earth. But when it rains contact with wet vegetation bleeds that off to 4-7kV, which will still keep experienced cattle in but probably not newbies. If it shorts it drops to 0.3kV or so. The real problem out here in the dry west is when it doesn't rain, which is 2/3 of the year. It gets so dry that the return path is no good - dry hooves, dry vegetation, dry soil and dry grounding rods. The voltage then will be only 1kV or so, and after a few days the cows figure that out. The same thing can happen in dry washes - they won't get shocked walking on rocks like on soil.

So you need to run a second perimeter wire that's connected back to the charger's ground to bypass the earth return and maintain your full power zap. I run one strand barbed wire anyway in case it gets shorted, and it serves the same purpose.

Interesting note about training cattle to an electric fence for the first time: Ideally you want them to approach it obliquely and slowly, so that the first contact is on their face. Then they recoil away from the fence and figure out what shocked them. If they get shocked anywhere behind the eyeballs the first time they'll bolt FORWARD, right through the fence and have no idea what just happened!
 
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