I believe the butterfly vario has an adjustment of how much you want to 'mix in' the accelerator/gyro with the TE. I hear the recommended setting has increased over time so they must be getting more confident. Current the big advantage of these new varios is instantaneous wind information. I can see that being very useful in the mountains. On 23 May 2014 01:29, "Scott Penrose" <[email protected]> wrote:
> Yeah I heard rumours about the butterfly not actually using the internals. > > Thanks Mike > > Scott > > On 23 May 2014, at 2:07 pm, Mike Borgelt <[email protected]> > wrote: > > At 12:35 PM 23/05/2014, you wrote: > > The newer generation Varios still use TE but have inertial sensing as an > adjunct to TE to assist with gust filtering. > > Regards, > John Orton > Mob: 0429357439 > > > The inertial versions do (ie. ones that don’t use a TE tube). > One other valuable feature I think is a good Artificial Horizon. > > I agree though that I would rather use external device (I use XCSoar) for > glide computer (final glide, navigation etc). > > Scott > > > > You don't need a TE tube to do a total energy vario based on pressure > measurement but there are many problems introduced by this which is why > most varios that offer this also can use a TE probe. The main problems are > that you are taking the difference between two large signals and if they > don't arrive at the vario at the same time you get large transient false > indications. The other problem is that a pitot and static source on a > glider are far more sensitive to yaw and pitch changes than is a good TE > probe. You may as well just use the TE probe. > > The so called "inertial" varios no doubt have the 3 axis > accelerometer/gyros and magnetometer built in (same kind of thing as in > your iPad and maybe even the same device, they are only a few dollars) but > whether or not anything useful is done with them is another matter. They > may be there for advertising purposes. I was advised to put them in the > B600/B800 and advertise that but not do anything with the data. If you buy > a vario with inertial sensors ask what exactly is done. It is a good bet > that you will get some figurative arm waving and talk of "Kalman Filters" > without an actual good explanation. > > It is fairly easy to build a variometer (not TE compensated) using the > inertial techniques but a total energy variometer is far more difficult. Or > at least one that is a *good* vario with low zero point drift, like all > modern pressure transducer varios. The MEMS (Micro Electro Mechanical > Systems) accelerometers are pretty good but the gyros are fairly horrible. > They look good when you sit them on the bench and integrate the output to > get attitude (they measure *rate* of roll, pitch and yaw you need to > integrate these to get attitude changes from the start attitude) but are > terrible when moved around due to something called cross axis coupling and > output noise (no, the noise doesn't average out to zero). Been there, done > that. > > Inertial measurement units that will work are still quite expensive, of > the order of USD10,000 for the bare sensor and even then by the time you do > all the reference frame transforms and put it in a dynamic flight vehicle > (read glider) you'll probably find the error budget has got out of hand. > > A human pilot filters out horizontal gusts by "seat of the pants" i.e. the > vario is now showing lift but did I feel the vertical acceleration? The > problem is that sometimes the onset of lift is very gentle and your push or > pull on the stick can mask it easily. Sure it is simple to use an > accelerometer to detect vertical acceleration but how do you remove the > pilot inputs on the stick? Removing them is what total energy varios are > about but by measuring the airspeed you make the vario respond very well to > small rapid changes in airspeed caused by horizontal gusts as well as small > rapid changes in vertical motion of the air. This makes the vario more > difficult and tiring to interpret. > > Anyway, our upcoming* Dynamis *system solves all these problems and can > be added to B600 or B800 variometer systems. > > Mike > > > > *Borgelt Instruments* - > *design & manufacture of quality soaring instrumentation since 1978 * > www.borgeltinstruments.com > tel: 07 4635 5784 overseas: int+61-7-4635 5784 > mob: 042835 5784 : int+61-42835 5784 > P O Box 4607, Toowoomba East, QLD 4350, Australia > _______________________________________________ > Aus-soaring mailing list > [email protected] > To check or change subscription details, visit: > http://lists.internode.on.net/mailman/listinfo/aus-soaring > > > > _______________________________________________ > Aus-soaring mailing list > [email protected] > To check or change subscription details, visit: > http://lists.internode.on.net/mailman/listinfo/aus-soaring >
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