[PSUBS-MAILIST] gyroscope/fluxgate compass

Sun Dec 7 14:14:37 EST 2014

I used a similar flux gate compass setup for the R300 as mentioned by Emile with similar results.  I use a Ocean Server OS5000. http://www.ocean-server.com/compass.html  I designed a 1-atm anodized aluminum (6061) housing that is externally mounted to the pressure hull behind the viewport.  Like Emile, I found that the steel hull affected the results by about 5-10  degrees but the unit has an "hard iron" calibration process to calibrate out the error.  I plan on using the same unit for the R500.  BTW, the sensor also gives the tilt, roll and temperature in addition to the heading.  For my application, I have the electrical connections coming through an electrical penetrator and then connect via an RS232 connection to my PLC.  In the PLC ladder logic, I have to parse an ASCII string to extract the four measurements.  

Cliff

 From: Alan James via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Sunday, December 7, 2014 12:32 PM
Subject: Re: [PSUBS-MAILIST] gyroscope/fluxgate compass

Hi Emile,
did you have it displaying on a Raymarine screen?
Can I feed this in to a plc & display it on a screen easily?
It is saying......
COMPASS

    SeaTalk1

The Fluxgate Compass transducer is compatible with the ST40 and ST60+ instruments on the SeaTalk1 network. The transducer simply connects to the back of one of the following instruments:
	* ST40 Compass
	* ST60+ Compass

SeaTalkng

The Fluxgate Compass transducer is compatible with the i70 , ST70 and ST70+ instruments on the SeaTalkng network via an iTC-5 transducer converter (sold separately). The transducer is connected to the iTC-5 which converts the transducer signals to SeaTalkng. The iTC-5 is then connected to your SeaTalkng backbone.

Note that if your system contains an SPX autopilot the Fluxgate Compass should connect directly to the course computer and not the iTC-5.
Alan 

 From: Emile van Essen via Personal_Submersibles <personal_submersibles at psubs.org>
To: 'Personal Submersibles General Discussion' <personal_submersibles at psubs.org> 
Sent: Monday, December 8, 2014 2:19 AM
Subject: Re: [PSUBS-MAILIST] gyroscope/fluxgate compass

I got good results with a
(raymarine) fluxgate.  The sensor is placed in the all aluminium bow section ( 0,9 Meter away from the
hull) and the readout can placed anywhere. 
It can electronically compensate
10 or 12 deg deviation caused by the steel.  The sistership has the sensor in a
short mast also with good results. 

Attached a sketch of the
pressuretight sensor housing. 

Regards, Emile 

Van:Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] Namens " Carsten Standfuß "
via Personal_Submersibles
Verzonden: woensdag 3 december
2014 20:46
Aan: Personal Submersibles General
Discussion
Onderwerp: Re: [PSUBS-MAILIST]
gyroscope compass  

Gyros in aricraft are not north stable - they
need a magnetic compass or other device to set course. But they are
okay  if you set course according to your GPS course before you dive. They
can hold the course for some hours with a movment of 2-4 deegre per hour. Okay
for a slow and small Psub. They are vaccum driven or electric. Vaccum driven
you can not use in a small submarine. (Or you need a silencer and eardrums as
in Spurdog). Electric you can use if it is a 12 or 24 V DC driven one. For
other voltage you need a special power converter. The Ebay units are sometimes
cheap - between 100-800 USD - but most of them work not proper. They are
build out of the planes for exact that reason and sold as they are and without
any waranty.. Size is around 100x100x400mm. Volume 4 Liters .. Good solution
if you buy a unit in aircraft condition with papers from a aircarft surplus
dealer with a working garanty. Make sure that they get not wet or 100%
humidity. 

Gyros in ships are north stabilzed. The need around 40 Minutes to warm up. They
are much bigger - the smallest one are around 300 x 400 x 300 mm . Volume at minimum 36 liter . They need no
calibration or reference and they are stable over month/years. Problem is that
they normal switch on in a ship and never switch off.. If you switch of them -
make sure that you not move the sub in the next hours - otherwise they can be
damaged. They are expensive - about 30000 USD new and 3000-9000 USD second
hand.  There life time is limited 30000 -  40000 hours between first
failtures. 

I have both types in the Euronaut. And a magnetic one also. 
The gyros are both cheap Ebay ones. One from a aircraft one from a ship. 
And both not working anymore. And the third magnetic one has a big error
because of the 60 ts steel below. 

I will by next a second hand one north stabilzed ship gyro for around 3000 USD
from a ship scrap yard electronic dealer with a confirm that they test it and
its run stable but without any further waranty. 

A fluxgate its a kind of electronic coils magnetic field compass and will in
most cases not work proper on a strong magnetic metal shell like a submarine
with strong electric motor fields etc. To test on your submarine if these cheap
devices runs on you submarine install a simple magnetic compass temporary on
the sensor spot in mind and than turn the submarine 360 degree. Switch on
and off all electric devices. 
Cross check with another compass (or the same  one) far away from the sub. 

In most cases an electric 12 or 24 V Dc driven Airplane direction gryro in
combination with a gps course before diving will do the job. But in 99% a ebay
100 USD item will not work proper. 

vbr Carsten

"hank pronk via Personal_Submersibles" <personal_submersibles at psubs.org>
schrieb:
> 
> There are all kinds of them on ebay for under 100 dollars, problem is how
to make it work. I assume they just have a small motor that spins. There is a
nice ship gyro sitting at 50 dollars right now but it is about 1 foot dia. That would be
awesome in a big sub.
> Hank --------------------------------------------
> On Wed, 12/3/14, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org>
wrote:
> 
> Subject: Re: [PSUBS-MAILIST] gyroscope compass
> To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
> Received: Wednesday, December 3, 2014, 1:48 PM
> 
> Absolutely. You can get small ones for civil
> aviation and they are used in subs. One challenge is that
> most airplane ones are powered by a vacuum, but there are
> 12V models. Unfortunately they're expensive, but a great
> solution if you can afford it. 
> Alec 
> On Wed, Dec 3, 2014 at 1:28
> PM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
> wrote:
> Hi
> all,
> 
> Ever hear of a gyroscopic compass, seems that ships used to
> use them.  It seems they would not be effected by a
> submarine hull.  What am I missing besides they are very
> big.
> 
> Hank
> 
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