Reader Feedback
by J. Shuman
You will find a listing of pre-trimmed
Hall Effect Current Transducers
with input ranges of 6 to 100 amps
full scale at prices ranging from
$19.00 to $30.00.
These transducers require only
a source of + 5 VDC or ± 12 to 15
VDC excitation at a few milliamps
with an operational amplifier or
simple resister network for output
scaling. Since primary-secondary
coupling is through a Hall Effect
element, the transducer is
electrically isolated from the line.
These units cover an input
frequency range of 0-200 kHz. For
units up to 1,000 amps, check the
F. W. Bell Company.
For instruction of hobbyists on
more modern technologies, an
article in your publication on the
Hall Effect would seem to be in
order.
Dear Nuts & Volts:
Your feature article in the April 2004 edition of
Nuts & Volts, "Magnetic Saturation and the 100 Amp DC
Current Transformer" seems to be an attempt to reinvent
the wheel.
Edward H. Hall discovered the Hall Effect in 1887.
Hall Effect elements were coupled with semiconductors in
the 1970s, all but eliminating the use of wire coils wound on
square loop cores for metering and control (magnetic
amplifier) purposes.
If you need to measure high DC currents, look in your
Digi-Key catalog under "Transducer-Current" (page 1,227).
Farnham Cornia
via Internet
The existence of pre-made Hall Effect transducers does
not eliminate the value of explaining the electromagnetic
theory behind the operation of Mr. Glenn's circuit. —
Editor Dan
Dear Nuts & Volts,
The June issue — page 95 — in “Tech Forum” has a
schematic for a Gel-Cel Charger. The parts list appears to be
missing a steering diode that is connected to the plus
terminal of the battery. I suspect it is
a low voltage GP silicone diode rated
at 1 or 2 amps — something like a
1N4001.
F
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NUTS & VOLTS
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6
Lynn Weber
Austin, TX
Dear Nuts & Volts:
You had me ... hook line and
sinker with the April
“Techknowledgey 2004” column.
Then co-worker David M. LeBlanc
noticed the little red box in the lower
right hand corner of page 79. From
there, it was easy. The fly eats near
the golden arches — probably leftover
Big Macs just casually dropped by a
not-so-hungry Martian. Good April
Fools picture (and article).
I really enjoy your magazine
regularly.
Elmer Bourque
Fredericton, New Brunswick
Canada
JULY 2004
