Hi Chris and all,

Chris's sensitive "distance calibrator" that was used for his Hall
sensor/s, output graph measurements can be seen at:

http://seismograph.tripod.com/distancecalibrator.html

It was very well crafted by Chris himself, and well worth a peek.

Take care, Meredith Lamb

ChrisAtUpw@....... wrote:

> The resolution and the linearity that you can get from a $1.83
> A3515LUA sensor from http://www.newark.com/ and a $2 type #2 NdBFe
> four pole magnet from www.wondermagnet.com are really quite good.
>
>     The minimum movement which can be measured depends on the
> sensitivity and on the noise level present on the output signal. With
> a three pole 10 Hz Butterworth filter and the NdBFe magnets set for a
> sensitivity of 5.8 mV / micron, an A3515 sensor gave a bit under +/-20
> nano metres resolution and the linear range of 0.8 mm. If I increased
> the sensitivity to 10 mV / micron by adjusting the magnetic field, I
> got down to about +/-10 nano metres resolution, but I had only ~0.5 mm
> total linear range. This is still OK for a pendulum sensor.
>
>     See http://mariottim.interfree.it/doc11_e.htm for a typical
> calibration graph and some further notes on these sensors.
>
>     Regards,
>
>     Chris Chapman


Hi Chris and all,
Chris's sensitive "distance calibrator" that was used for his Hall

sensor/s, output graph measurements can be seen at:
http://seismograph.tripod.com/distancecalibrator.html
It was very well crafted by Chris himself, and well worth a peek.
Take care, Meredith Lamb
ChrisAtUpw@....... wrote:
The resolution
and the linearity that you can get from a $1.83 A3515LUA sensor from http://www.newark.com/
and a $2 type #2 NdBFe four pole magnet from www.wondermagnet.com
are really quite good.
    The minimum movement
which can be measured depends on the sensitivity and on the noise level
present on the output signal. With a three pole 10 Hz Butterworth filter
and the NdBFe magnets set for a sensitivity of 5.8 mV / micron, an A3515
sensor gave a bit under +/-20 nano metres resolution and the linear range
of 0.8 mm. If I increased the sensitivity to 10 mV / micron by adjusting
the magnetic field, I got down to about +/-10 nano metres resolution, but
I had only ~0.5 mm total linear range. This is still OK for a pendulum
sensor.
    See http://mariottim.interfree.it/doc11_e.htm
for a typical calibration graph and some further notes on these sensors.
    Regards,
    Chris Chapman