Hi all,
I completed the Rogowski-coil project this evening. Mine is a version
for the SLF/ULF/VLF range, covering 0.1...10 kHz. Of course a version
for LF can be built too.
The coil is now protected with shrinking tube. It feels very robust.
The circuit consumes 8 mA from a 9V battery. It integrates the voltage
to get rid of the di/dt dependency and provides a output voltage of 1V
at 1A RF. This ratio is very stable (< 3%) inside the design frequency
range. Also the linearity is more than adequate. The current range is
0...2A, so the current can be measured with a 2V AC digital multimeter
(covering that frequency range).
The attachemnt shows the portable system which does now allow to measure
RF currents into larger metallic parts, such as towers, or guide rail
poles! :-)
Oh and you can measure the antenna current on the hot side of the coil,
or along the wire, even if it carries 20 kV. The coupling capacity will
be negligible.
A second attachment shows the schematic, just to give an idea.
No, this is not new (unfortunately necessary to mention this, before
someone can't resist to do so)! But anyway i did not see someone else
using such a technique since the almost 10 years i'm here on the reflector.
Indeed it could be helpful to measure how much antenna current is still
flowing in the wire after some meters where a tree pulls away a part of
it. It may help to check if it is worth to remove the tree, or, to move
the coil behind the tree (on the cost of a lower capacity and thus
higher losses for a larger coil )...
73, Stefan
PS: A practical test will follow in some days...
Am 24.10.2018 20:48, schrieb DK7FC:
...now the coil is completed, see attachment.
Some first measurements:
Diameter: 0.3 m.
R (DC): 17 Ohm.
Inductivity (measured at ~ 1 kHz): 1.62 mH
Self resonance: 734 kHz
So far so good...
73, Stefan
Am 23.10.2018 15:13, schrieb DK7FC:
...now i started to build one, see attachment.
Not yet sure how it will perform. DON'T bother me with calculations
telling it won't work! ;-)
73, Stefan
Am 22.10.2018 15:04, schrieb DK7FC:
Hi all,
Has someone ever build (homemade, not bought!) a Rogowski-coil for
RF current measurements?
https://en.wikipedia.org/wiki/Rogowski_coil
It could be used to measure leakage currents in a tower near the
antenna wire for example. Or for measuring RF currents into a pole
of a guide rail, for example :-)
I'm planning to build one and i thought i use 0.4 mm diameter
enameled cu wire arround a graden hose, having 0.6m circumference.
Then some shrinking tube will be applied. That's the plan.
The circuit looks easy, it should be run from a 9V battery and a
simple TL081 for example. The output could be adapted to a
multimeter, so there is a digital read-out.
I'm curious to see how it works...
73, Stefan
Rogowski_coil_scheamtic2.jpg
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