Fusor Forums

When using capacitance across the resistors for HF response you need a variable cap across the Low voltage resistor at the bottom of the string to get the proper HF response.

Adjust the Variable cap so that a square wave into the sting looks like a square wave at the scope.

Wallace, Allen wrote:

> The idea is to keep the HV away from meters during a fault condition.

Has anyone considered, or used, optical effects like Brag,
Faraday, Kerr or Pockels to measure high current/voltage? I know
AB&B uses/used Pockles in some of their high-tension switching
gear.

For sake of example, as it would be tough in practice to get this
to work finding the correct fiber cable material etc, you could
wrap some Fiber Optic cable around a high voltage wire. You put
a light source of a known polarization into one end of the fiber,
and the polarization of the light is changed in proportional the
high voltage potential, which is measured on the other end of the
fiber.

There is also the more mundane use of fiber optics where you put a
micro and A/D at the high voltage end, and use fiber or IR/IrDA to link
back to the instrument panel. You don't have to worry about
meter faults turning in to electrocution hazards.

If plastic optical fiber would work, let me know. I have significant quantities of surplus plastic optical fiber approx 0.004" diameter hundreds of yards long, and limited quantities of glass in short lengths (approx 0.001" up to 10 feet long). Precise chemical composition of the fibers is not known (if this is relevant), but the fiber was intended for illumination applications, not data transmission.

Dave

> Has anyone considered, or used, optical effects like Brag,
> Faraday, Kerr or Pockels to measure high current/voltage? I know
> AB&B uses/used Pockles in some of their high-tension switching
> gear.
>
> For sake of example, as it would be tough in practice to get this
> to work finding the correct fiber cable material etc, you could
> wrap some Fiber Optic cable around a high voltage wire. You put
> a light source of a known polarization into one end of the fiber,
> and the polarization of the light is changed in proportional the
> high voltage potential, which is measured on the other end of the
> fiber.
>
> There is also the more mundane use of fiber optics where you put a
> micro and A/D at the high voltage end, and use fiber or IR/IrDA to link
> back to the instrument panel. You don\\'t have to worry about
> meter faults turning in to electrocution hazards.

> Precise chemical composition of the fibers is not known (if this is relevant),

Unfortunately the material does mater. Some of it is quite toxic for the Kerr
type, that is generally why expensive Pockles crystals are used.

> but the fiber was intended for illumination applications, not data transmission.

Still might work A/D isolation type.

Bob Paddock wrote:
> > Precise chemical composition of the fibers is not known (if this is relevant),
>
> Unfortunately the material does mater. Some of it is quite toxic for the Kerr
> type, that is generally why expensive Pockles crystals are used.
>
> > but the fiber was intended for illumination applications, not data transmission.
>
> Still might work A/D isolation type.

Bob,

If anyone wants to try some, eMail me privately, and I'll send you some. I have a lot of material stashed away, but tomorrow is the last day, as the factory will move to Juarez, MX, to take advantage of lower labor costs. Sigh....

Dave

If the voltmeter you have reads DC, you can simply do the same thing you are currently doing, only instead of the divider, you can replace it with a high voltage diode and switch it to positive right before the meter.