[Johnson] Shunt Resistors...

[Eddy Swynar]

Hi All,

In the past I've made many shunt resistors for different metering
applications simply by winding the appropriate-size enamel wire on a piece
of BIC-brand plastic disposable pen...once I even wound one a piece of
varnished 1/4" maple dowel rod!

Cut a piece of the pen body about 3/4" - 1" in length, drill two VERY small
holes clean through the body at each end, then fish the end of the enamel
wire through one...scramble-wind the wire on the "form", & feed it through
again at the end. For additional strength, I've slipped a short pieces of
stiffer, thicker wire through these holes to act as terminal posts for the
enamel wire, & to extend outward to reach the meter terminals.

The math is easy: once you know the resistance needed, figure out the length
of wire needed to achieve it for the size of enamel wire you have on hand
(consult the wire table in any of the older ARRL HANDBOOKs), then cut.
Remember to NOT exceed the current-handling capability of the wire for the
application!

As a final measure (no pun intended), compare the readings on your "new"
meter to one temporarily put in place of a known calibration...

I've never been too far off by doing this.

~73!~ Eddy VE3CUI - VE3XZ