Capacitor Guide

[Nick]

Further to the "resistor guide" site mentioned by Lawrence, the same people have also done a "capacitor guide".

http://www.capacitorguide.com/

Again, the site is very useful - doesn't go into too much detail, but good sound information.

[pwdrive]

The resistor guide does have the odd typo error in it but all in all I found it useful as I found the answer to obtaining low inductance values in wire wound resistors, how did I end up there? Looking for stuff on magnetic loop antennas both shielded and unshielded, that led to the "Mobius Antenna" amongst others and by some quirk that led me to Aryton-Perry windings and that trumped up on the resistor site.

Lawrence.

[Nick]

Arcol have special "low inductance" variants of their Al resistors - you just add an "N" before the part number, e.g. NHS50xxxx etc. and their vitreous enamel (the "V" series) resistors.

http://www.arcolresistors.com/wp-content...-05.45.pdf
http://www.arcolresistors.com/wp-content...-13.06.pdf

These resistors do actually use Ayrton-Perry windings.

The reason that the maximum ohmic value is 25% of the normal range is that with, say, a 10R resistor, they divide it in 2, wind in the Ayrton-Perry style, then connect the two windings in parallel, hence 1/4 of the original value. Note also that the maximum voltage is derated by a factor of root 2 (i.e. 1.414).

Arcol claim that this results in the NHSxxx components having 12% (one eighth) of the inductance of the equivalent HSxxx value.

My own 200W dummy load uses 2 x 15R BDS100 in parallel in series with 2 x 1R RCH25 in parallel to make exactly 8 ohms non-inductive all clamped to a LARGE heatsink. This was expensive but a client paid for it :-)