Xref: utzoo sci.electronics:7708 rec.models.rc:1944 rec.aviation:16938
Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!iuvax!daemon
From: commgrp@silver.bacs.indiana.edu (BACS Data Communications Group)
Newsgroups: sci.electronics,rec.models.rc,rec.aviation
Subject: Electronic variometer plans wanted
Message-ID: <25730@iuvax.cs.indiana.edu>
Date: 8 Sep 89 20:27:20 GMT
Lines: 31


to sci.electronics, rec.aviation, rec.models.rc

I need references and construction details for electronic vertical-
speed indicators (called variometers by sailplane pilots).  I'm told 
that plans have been published in magazines of soaring and remote-
control aviation.

The device is basically a hot-wire anemometer. Some designs use bare 
filaments of flashlight bulbs in a bridge circuit.  The cooling effect 
of wind on two of the filaments changes their resistance in proportion 
to velocity; the other two filaments are shielded from wind and used 
as a reference.  The variometer has an accumulator tank connected to 
outside air through a small orifice in which is mounted the hot-wire 
sensor. Air from the tank flows outward when an aircraft climbs, 
inward when it descends, i.e., the instrument is a differential 
barometer/altimeter.  I don't know how the hot-wire circuit senses 
direction of air flow.

Some of these devices are intended for manned sailplanes and 
ultralight aircraft, others are used for telemetry from radio-
controlled model sailplanes.  I am especially interested in the latter 
type.  I intend to use it for studies of barometric wind in caves.

Will pay reproduction and mailing costs.

Thanks in advance,

Frank Reid     W9MKV @ K9IU     C,I,SEL     NSS 9086F
P.O. Box 5283
Bloomington IN 47407