Re: Fiber Optic V & A Meters

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

Led and phototransistor, using the inexpensive 1000 micron plastic fiber, is
fairly linear.. (at least better than the 5-10% FS of an analog meter).

If you want fancier, use an op amp, drive two LEDs in series, put one
photoreceiver in the feedback loop of the op amp.

Other strategies are to use a Voltage to freq converter to drive the LED...

DC current probes are about $20 (based on Hall effect sensors) (from
Honeywell, and others.. check the catalogs).. you can easily put 50kV
insulated wire through the hole.

For the voltage, you can just use a suitable divider, and put your meter at
ground.  A string of 30 Meg resistors won't load it much, and the precision
is fairly good.


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, August 24, 2002 10:23 PM
Subject: Fiber Optic V & A Meters


> Original poster: "S & J Young by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<youngs-at-konnections-dot-net>
>
> I like to measure KV and mA supplied by my filtered DC supply while it is
> powering my twin TC.  The supply is plus & minus 10KV, center grounded (4
> MOTs, twin doublers).  I now use analog meters directly wired into the HV
> and have the meters located away from the coil so I can read them without
> getting streamer zaps.
>
> I don't like the meters floating at high voltage - not safe.  I would like
> them isolated by optical fiber cables.  If I use a simple LED and
> phototransistor combination, or LED and photodiode and op amp, what
> linearity can I expect?  I need to measure 0 to 20 KV and 0 to 200 mA.
>
> If any of you have built fiber isolated V & A meters, please share details
> and results.
>
> Thanks,
> --Steve Young
>
>
>
>