[PSUBS-MAILIST] Re: Compass instruments

[MerlinSub@t-online.de (Carsten Standfuss)]

Hi Alec, nice to hear from you - I still think that "Solo" is the best
choise for a name of a selfbuild onemansub ;-) The question is so good
that I transmit the answer to Psubs... 

I found out that an aircraft gyro need to be compensate all 10-15
minutes by a .. magnetic compass.. Its not a joke - on smaller crafts
the pilots do it by hand - fly straight course, same speed and level
than turn the compensate switch with his eyes looking on the magnetic
compass. 

On bigger or modern aircrafts this compensation is done automaticly by
an interlink between the gyro and the magnetic compass.. The reason for
that is that a ships gyro - which is north stabilzied needs some time
(hours) before he works properly - and is much bigger and heavier. 

I go this way : An aircaft gyro compensate by hand with the information
form a pretty small magnetic fluxgate sensor about 1.5 (5 feet) on top
of the sail at on one of the radio antennas. 

The only question concerned me : Is there a problem with the radio VHF
antenna and the fluxgate magnetic sensor ? 

See you Carsten

Alec Smyth schrieb:
> 
> Carsten,
> 
> I've finished my power distribution panel and am now getting into the instrumentation for depth, life support, navigation, etc. One of the basic decisions is what to do about a compass.
> 
> I see two possibilities; Cliff Redus's approach using an integrated circuit outside the hull, or an electric directional gyro inside the hull. I don't like the outside the hull approach because it would imply a hydrodynamic drag and might not even work given the amount of steel around.
> 
> I remember a month or two ago you were asking about gyros. Did you find anything reasonably priced? D'you know if they can be interfaced to a PLC?
> 
> thanks,
> 
> Alec