Fence testers: why the cheap one tells you the least useful fact

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Research. Bought, not yet lived with. This is what the different kinds of tester do and which one we chose to start with; the durability verdict comes after it has spent a year in a coat pocket.

There are three ways to find out whether an electric fence is live, and only one of them is any good.

The three ways

Touch it. Free. Tells you the fence is on. Tells you nothing about how well, teaches you nothing you can act on, and is a poor habit to build in front of children.

A neon tester. The cheap pen-style one with a bulb. It glows if there is voltage. It will not tell you how much, which means it cannot tell the difference between a fence that will turn a heifer and a fence that will merely annoy one. Both make the bulb glow.

A digital tester. Gives you a number in kilovolts. This is the one worth owning, and the gap in price is smaller than the gap in usefulness.

What the number should be

Rough working figures:

• Above 5 kV — a fence doing its job for most livestock.
• 3 to 5 kV — working, but something is drawing it down. Usually vegetation.
• Below 2 kV — the animals already know.

The value of a number rather than a glow is that you can walk the line and watch it fall. The place where it drops is the place with the problem. A neon tester makes every point on the fence look identical right up until the fence stops working.

The feature worth paying for

A fault finder. Some digital testers show not just the voltage but the direction and size of the current leak — so instead of walking the whole fence, you stand at a point and it tells you which way the fault is.

On a long fence that is the difference between a ten-minute job and an afternoon. On a short one it is a luxury. We are short, for now, so we did not buy it, and I expect to regret that the first time a wet limb comes down at the far end.

What it does not fix

A tester tells you the fence is weak. It does not tell you why, and the answer is nearly always one of three things:

1. Vegetation touching the wire. Most common by a distance. 2. A bad ground system — too few rods, too short, or badly clamped. See the charger page, because this is the thing most new fences get wrong. 3. A broken insulator letting the wire touch a post.

Check them in that order. It is that order roughly every time.

What we bought

The tester is bought and not yet lived with. The make and model are not in this section yet, and that is deliberate: a name printed the week a tool arrives is only the box repeated back. It goes here once the thing has been carried a while, alongside what it cost and whether the money landed in the right place.

The fault finder is not an open question. The line is short, so we went without one. That is a decision this page has already made, not one it is still weighing.

Durability is what is left. No specification sheet tells you whether a case survives being sat on, or whether the reading stays honest after a season of damp. A year in a coat pocket settles that, and the Research tag at the top stands until the year is up.

Before you buy

• Get a digital one with a number on it. The neon pen is a false economy — it tells you the least useful fact about your fence.
• Keep it where the fence is, not where the tools are. A tester in the shop is a tester you do not use.
• Test after you build, not the first time something gets out.

— Chris D., McEwen, Tennessee