On Nov 6, 5:59*am, wrote:
snip
Does this system controller measure the speed by reading a
voltage
from the sensor (with voltage being proportion to wind speed) or
is it
counting pulses (1, or N pulses per revolution, hence frequency
is
proportional to speed)?

If it's counting pulses, then I might suspect either of:

It is indeed counting pulses.

- *A "bouncing" switch in the sensor, which is just barely making
* *contact at the point at which the sensor has stopped spinning,
and
* *is vibrating open and closed. *The cure for this would be a
better
* *sensor-switch - one with enough hysteresis that it opens or
closes
* *firmly and doesn't jitter back and forth.

It is not a mechanical switch. * The pulse generator consists of an
IR
LED that shines on IR sensor with a plastic disk in between that
has a
series of black stripes painted around the edge of it. When the
wind
cups spin, the disk spins so the black stripes interrupt the IR
path
between transmitter and sensor generating pulses. *The pulses then
to go
to a base of a transistor that I assume is a switching transistor
that
is either fully on or fully off. *It is an NPN transistor in common
emitter configuration and the output of that is fed directly into
the
CPU for counting the pulses in a given time frame for wind speed
determination.



- *RF interference from a local transmitter, with the RF signal
* *"looking like" contact opens and closures to the control unit.
*The
* *cure here would be some amount of RF snubbing being added to
the
* *line to the sensors - possibly wrapping the wires around some
* *ferrites, possibly adding a small amount of capacitance across
the
* *line to shunt out the RF, or possibly both.

I thought about the possibility of noise pickup and put some a
capacitor
across the line where it connects to the weather station and it did
not
seem to help.

Thanks for taking the time to reply.

Have you tried the simplest and just clean the disc and
semiconductors? We have tape machines at work with optical tachs that
require cleaning on occasion (many years between cleanings). My
Kensington trackball (optical tach) was screwing up last week, cursor
bouncing like your wind speed readings. A good cleaning has it working
well again.

GG