"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller
Thanks. The predecessor circuit, never published, was far more complex.
It occurs to me that a gradiometer circuit might be useful for detecting
nearby field generators at the expense of distant field generators.
If one uses two hall-effect chips separated by a known distance and
oriented the same way, if one feeds the outputs into opamp plus and
minus inputs, the output will be the field difference.
In my simple magnetometer circuit, if one replaces the 15K-500-15K
divider string with a second hall chip oriented the same as the first,
the difference in outputs will be reported by the voltmeter.
One can implement a differential sensor with two hall chips glued to one
another back-to-back. This may be useful because the Micronas HAL401
may be hard to buy in small quantities.
Analog Devices offers one linear hall chip, the AD22151, which appears
suitable as well, and should work in my simple circuit in place of the
Allegro chips (although the pin numbers will likely change). The
AD22151 is a little SOT-23 surface-mount chip, but I bet one can easily
solder magnet-wire leads to it, and make a nice little probe with it.
European for 6.2 Kohms - saves a whole decimal point, and avoids the
comma versus period debate. I also like the European approach to
resistor symbols - just a rectangle, much easier to draw.
Usually (not always) the term "trimmer" sort of implies a multi-turn
pot. (trimmer caps are usually 270-to-300-degree single-turn devices).
Since they only run a buck-plus at Digi-Key, that's the way I'd go.
Precise, reliable, and good for a couple K's of settings before you
wear out the wiper.
On Sun, 18 Jan 2009 18:34:26 -0500, the renowned Wes
For value it's hard to beat the 3/8" multi-turn trimpots. Sealed, 25
turns or so, and they have a clutch mechanism. They start at around $1
USD from Mouser or Digikey. (eg. Murata PV36 series).
"it's the network..." "The Journey is the reward"
email@example.com Info for manufacturers: http://www.trexon.com
Multiturn is essential. Single-turn will be impossible to set
accurately enough, and too sensitive to mechanical disturbance.
Other than that, it isn't critical. I used 25-turn cermet pots packaged
by NTE that are sold by the local electronics parts store (U-Do-It in
Needham, MA, off Rt 128 near Boston).
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.