ILEC Varios???
JShore3021
Specifically, what are the pros and cons of the ILEC SC-7 Club vario?
Are there any problems with the internal capacitance?
Thanks,
Jamie
James Tsillas
I purchased an SC-7 new this year and really believe it is
the best vario of its kind (club use or for those who don't need
fancy computers).
Among the pros: switchable time constants (1 sec for thermalling
3 sec for cruise works very well). Very sensitive and accurate
(compared to others I've seen - Ball, Cambridge, RICO). Built
in 24 sec. averager digital display (extremely useful). External
temperature and battery condition (nice but not 'must have'). As
you mention, it doesn't require any external capacity (this seems
to work well). Another thing I like about it is the tone it produces
via the audio - it is very pleasant and clear. GIven that 90% of
the time I use the audio exclusively, it is nice when the audio
is easy to listen to.
The only cons: vario arrived requiring calibration. This required I
open the case and fiddle with a tiny potentiometer. Directions on
doing this are included with the excellent manual. No adjustable audio
dead band. This means that if you want to hear the sink tone you must
listen to it even when you are cruising. I fly with the sink tone turned
off but I would prefer an adjustable sink tone dial where I can set it
to be below my cruise sink rate.
If you want a fancy flight computer you are not going to find it with
the SC-7 (obviously) but if you are looking for a good easy to use
instrument that does a splendid job for what is intended. Look no
further. The only thing I miss from the SC-7 is a netto mode but that
would require more plumbing and expense.
-Jim.
Thomas Knauff
JShore3021 wrote:
> In general, what is the reputation of ILEC varios?
ILEC is recognized as one of the major leaders in variometer technology.
The ILEC SC-7 is perhaps the most popular of all electric variometers.
Four of the five USA world team members used ILEC instruments.
--
Thomas Knauff
Schempp-Hirth Sailplanes
Knauff & Grove Soaring Supplies
3523 South Eagle Valley Road
Julian, Pa 16844
Phone (814) 355 2483
Fax (814 355 2633
Email: tkn...@earthlink.net
http://www.glider.com/knauff/
Jan Lustrup
>
> I purchased an SC-7 new this year and really believe it is
> the best vario of its kind (club use or for those who don't need
> fancy computers).
>
> Among the pros: switchable time constants (1 sec for thermalling
> 3 sec for cruise works very well). Very sensitive and accurate
> (compared to others I've seen - Ball, Cambridge, RICO). Built
> in 24 sec. averager digital display (extremely useful). External
> temperature and battery condition (nice but not 'must have'). As
Mike Borgelt
<jts...@atlas.ccs.neu.edu> wrote:
>you mention, it doesn't require any external capacity (this seems
>to work well). Another thing I like about it is the tone it produces
>via the audio - it is very pleasant and clear. GIven that 90% of
>the time I use the audio exclusively, it is nice when the audio
>is easy to listen to.
>
>The only cons: vario arrived requiring calibration. This required I
>open the case and fiddle with a tiny potentiometer.
Calibration against what?Why?
This may be because of the lack of altitude compensation of the hot
wire type flow sensors.This means that unless you are at the
particular pressure/temperature combination where the calibration is
correct, the calibration will always be wrong. It will still let you
center thermals but any kind of averager may well be misleading
and a digital averager seems a waste of time.
If you have a computer type vario, which does have altitude
compensation, in the panel as well , the two will nearly always read
differently.
I didn't like the thought of this so put in the altitude compensation
when I designed the B40. The absolute pressure transducer used for the
sensor allows this at only small extra cost and complication.( A
digital averager is an option.) It also uses little power and takes up
little space (no capacity flask- either internal or external) making
for a short vario which runs from a 9 volt battery for "get you home"
standby power with averager and audio functions. It's much better than
a Winter , PZL, Bohli or Sage for this. I found out about this half
way round a 500km task during an Australian Nationals when my elderly
gell cell gave up and I had great difficulty finding thermals in
cruise on my non audio electric back up vario.
Flow sensor electronic varios used to be about the only way the job
could be done (1950's) but advances in electronic sensor technology
have come along and all but two sailplane variometer manufacturers
have long ago changed to using silicon pressure transducers and I
don't believe that any hang glider/paraglider manufacturers still use
flow sensing. I don't think it's used at Boeing, Lockheed Martin or
Airbus either.
Mike Borgelt
James Tsillas
mbor...@ozemail.com.au (Mike Borgelt) writes:
> >The only cons: vario arrived requiring calibration. This required I
> >open the case and fiddle with a tiny potentiometer.
>
>
> Calibration against what?Why?
THe ILEC I received would indicate a consistent +0.8 knots up after
warming up on the ground. This is even when I had the TE port taped up
as suggested in the manual. I'm not sure why this happened but the
manual suggested that in this event, the vario can be adjusted via a
potentiometer located within the case. Fiddling with this potentiometer
brought the needle to 0 on the ground. Is possible that as a result I
may have distorted the reading at a lower pressure or temperature? It
seems that an instrument designed to measure change in pressure should
not require compensation for different altitudes (but perhaps for
different temperatures). Is this assumption wrong?
What are the major design differences you are aware of between Borgelt,
ILEC, Sage and Cambridge?
cheers,
-Jim.
Robert Perry
After replacing my broken Cambridge system with the B40 the
only thing I regretted was not buying a B50. The B40 worked
perfectly right out of the box. If it says you are going up you
are going up. Even half a needle width above 0. Which is often
the case here in western Washington State. And if it
says 0 you have probably "gone to the cows" :-)
-Bob
Mike Borgelt
On 23 Aug 1999 09:32:53 -0400, James Tsillas
<jts...@atlas.ccs.neu.edu> wrote:
>
>mbor...@ozemail.com.au (Mike Borgelt) writes:
>
>> >The only cons: vario arrived requiring calibration. This required I
>> >open the case and fiddle with a tiny potentiometer.
>>
>>
>> Calibration against what?Why?
>
>THe ILEC I received would indicate a consistent +0.8 knots up after
>warming up on the ground. This is even when I had the TE port taped up
>as suggested in the manual. I'm not sure why this happened but the
>manual suggested that in this event, the vario can be adjusted via a
>potentiometer located within the case. Fiddling with this potentiometer
>brought the needle to 0 on the ground. Is possible that as a result I
>may have distorted the reading at a lower pressure or temperature? It
>seems that an instrument designed to measure change in pressure should
>not require compensation for different altitudes (but perhaps for
>different temperatures). Is this assumption wrong?
Yes, it's wrong.
The pressure/altitude relationship in the atmosphere is non linear.
At sea level the pressure change in the atmosphere is about 37
millibars/1000feet (about 1inch of mercury/1000 feet). At about 22000
feet the pressure change is about half as much per 1000 feet causing
an instrument designed to measure rate of change of pressure to read
about half as much for any given constant rate of climb.
Fortunately in a pressure transducer based vario like the B40(or B50)
we have an absolute pressure signal available and with a little
electronic trickery the gain of the internal amplifiers can be
increased as the altitude increases resulting in close to correct
calibration at all altitudes in this range.
Flow sensor varios like the ILEC don't have the absolute pressure
signal available so cannot do this unless a pressure transducer is
added just for this purpose which increases the cost to the
manufacturer.
In your case though the issue is the stability of the zero point. If
it was off by 0.8 knots I'd have to question both its's long and short
term stability with regard to ambient temperature and age. This
matters when you are in a +/- 0.5 knot broken thermal and the first
indication you have that something is wrong is that after some time
the altimeter is unwinding. The averager is no help as it has the same
zero error as the vario itself. This problem was common in early (late
1950s early 60s) electronic vario designs and should not exist in
1999.
Zero stability is another place that pressure transducer based varios
rate highly. With proper circuit design the zero stability gets down
to around the +/- 0.1 knots or better over the operating temperature
range. Note that some flow sensor vario manufacturers will quote a
zero stability in terms of x %/degree/Full scale and to the
ininitiated the number looks quite small and impressive but it's a lot
less impressive when you multiply by the full scale 10 knots or more
and the number of degrees in the quoted temperature range.
Flow sensors also may have zero errors due to mounting attitude.
If the tube they are in is tilted the heated elements cause convection
and flow not related to rate of climb.
>What are the major design differences you are aware of between Borgelt,
>ILEC, Sage and Cambridge?
Sage is a purely mechanical vario system.
You could in theory build a sound system by connecting a speaker
diaphragm to a stylus arm without any electronics but don't expect
hi-fi! It's not quite as bad as this but I haven't had a mechanical
vario in a glider since late 1978.
Cambridge uses thermistor flow sensors and external capacity flasks
and doesn't altitude compensate the CAV II.
ILEC uses hot wire flow sensors(as far as I know) and a small internal
capacity again without altitude compensation in the low end products.
Borgelt uses pressure transducers in all vario products and we
altitude compensate all our varios from sea level to 22000 feet which
should take in about 99.9% of all soaring. We know about flow sensors
as we used to use thermistor flow sensors until 1982 when the pressure
transducer technology became good enough and inexpensive enough to
use.
Peschges, Zander, SDI and the Filser varios except the low end LX100
use pressure transducers. The LX 100 is also not altitude compensated.
All the varios will get you into the strongest lift but modern
technology can eliminate the nagging worry that what you see on the
dial isn't right. Raouf Ismail had an article in Soaring magazine
about 20 years ago relating to some vario zero stability and ergonomic
issues.
Mike Borgelt