Digital Electric Fence Tester?

[torgil@torgil.com]

Hi!

I've got an electric fence with 1Hz high-voltage pulses (2kV-10kV).
I'd like to monitor the voltage from the fence using an ADC. Could
anyone give me some ideas for a high-impedance circuit that could be
connected to an ADC?

Could I use a capacitor and a diode? Any ideas are welcome!

 

On Wed, 6 May 2009 05:49:32 -0700 (PDT), "torgil@torgil.com"
<torgil@torgil.com> wrote:

Hi!

I've got an electric fence with 1Hz high-voltage pulses (2kV-10kV).
I'd like to monitor the voltage from the fence using an ADC. Could
anyone give me some ideas for a high-impedance circuit that could be
connected to an ADC?

Could I use a capacitor and a diode? Any ideas are welcome!

You probably don't want a direct connection from the 2KV+ pulses to
solid state electronics.

Use a small transformer to pick up the magnetic field from the wiring
and have it drive a diode + capacitor to give an output that could be
measured by an ADC. No connection to the electric fence wiring, just
inductive pickup.

For a working/not-wrking sensor, use a neon bulb driving a photodiode
or phototransistor in a length of black plastic pipe. Run a wire from
one side of the neon bulb through a high voltage rated 10megohm
resistor to the electric fence wire. The neon bulb should be
triggered by the high voltage pulse often enough to provide an
indication of voltage present (don't think it can keep up with 1kHz).
Put low voltage Zener diodes on the photodiode/phototransistor leads
for a little more high voltage protection.

John

 

[Sjouke Burry]

torgil@torgil.com wrote:

Hi!

I've got an electric fence with 1Hz high-voltage pulses (2kV-10kV).
I'd like to monitor the voltage from the fence using an ADC. Could
anyone give me some ideas for a high-impedance circuit that could be
connected to an ADC?

Could I use a capacitor and a diode? Any ideas are welcome!

Use a large voltage divider, for example 10 2megohm resistors

in series with a 1 megohm potentiometer,2KV/20 gives 100v
fullscale on the potmeter. Use 10 resistors to avoid breakdown
of the resistors, and maybe put those inside a plastic tube,
not on a small print, that might break down .
Put a SMALL neon lamp on the potmeter, and you can calibrate
the potmeter scale in KV.
or use a good quality digital peak voltmeter to read the 1megohms
resistor voltage.

 

[whit3rd]

On May 6, 5:49 am, "tor...@torgil.com" <tor...@torgil.com> wrote:

Hi!

I've got an electric fence with 1Hz high-voltage pulses (2kV-10kV).
I'd like to monitor the voltage from the fence using an ADC. Could
anyone give me some ideas for a high-impedance circuit that could be
connected to an ADC?

Could I use a capacitor and a diode? Any ideas are welcome!

Most folk already HAVE a digital electric fence tester. Why,
I have five of 'em on my left hand alone...

An HV capacitor and diode will pump a small amount of charge
each time the fence fires, and you could make a meter show
the rate x peak-voltage that way; if you don't trust the repeat rate
to be constant, or the peak shape to be unchanging, it's harder.
Either a second diode, or resistor to ground, will be required to
handle the AC output of the capacitor (so the low-V terminal
of the capacitor is near GND until the pulse arrives).

There are such things as electrostatic voltmeters, too.
The easiest route, if you have access to the driving unit, is
to look at the voltage on the PRIMARY side of the coil, it's
proportional to the output voltage but at much more convenient
levels for meters and such (maybe 500V).