NASA Speed / Distance instrument

[morgandlm]

I was experiencing intermittent failures of the paddle wheel operated speed readout last year when the indicated speed would drop to zero and only sometimes re-start. I put this down to a fouled wheel but the problem has continued this year (with a clean hull and paddle wheel). I have discovered that waggling the connection at the back of the instrument when underway will always restart it. Despite cleaning the contacts to try to ensure good continuity, the problem continues. I could send the instrument back to NASA to test but before doing so would like to test it myself. A simple test can only be achieved by being underway or by manually spinning the paddle wheel in which case I can't be at the instrument. I want to find out whether the fault is the instrument, the cable or the connection.

I assume that the paddle wheel sender simply sends a series of pulses which are counted at the instrument. I propose to use an Arduino to produce a series of 5v, low amperage pulses to test the instrument. Will this work? Can anybody advise what form the signal takes from the paddle wheel?

Any advice welcome

David Morgan

 

[Major_Clanger]

I have a paddle wheel you can borrow to prove the unit. Blackwater based.

 

[pvb]

I assume that the paddle wheel sender simply sends a series of pulses which are counted at the instrument. I propose to use an Arduino to produce a series of 5v, low amperage pulses to test the instrument. Will this work? Can anybody advise what form the signal takes from the paddle wheel?

I believe the Nasa log sensor has a simple coil which generates a small signal as the paddlewheel magnets pass it. Feeding 5v pulses into the display might damage it. You need to phone Nasa for a definitive answer.

 

[morgandlm]

Thanks pvb and Major-Clanger ... I had always intended to contact NASA Marine but simply hoped that someone would have a simple solution.

DM

 

[ghostlymoron]

I had a problem with mine too. It was always solved by replacing the paddle wheel and spindle. Cleaning and polishing it didn't work. If you can borrow a transducer and substitute it, that will tell you whether it's sender or processer. NASA customer care people are extremely helpful and knowledgeable. Give them a ring not email.

 

[pvb]

I had a problem with mine too. It was always solved by replacing the paddle wheel and spindle.

It's hardly likely to be the OP's paddlewheel if he can fix it by wiggling the connection on the instrument!

 

[ghostlymoron]

I find that its best not to jump to conclusions when trying to diagnose a problem so positively eliminate what yo can.

 

[pvb]

I find that its best not to jump to conclusions when trying to diagnose a problem so positively eliminate what yo can.

Often a good way to proceed, unless, like me, you find it impossible to believe that a dodgy paddlewheel could be cured by wiggling the plug on the back of the instrument head.

 

[yerffoeg]

I have given up with their paddle wheel log (no worse than the others) . When its not working at all it is under-reading because of fouling. I sold off the paddlewheel and have just fitted NASA's new electromagnetic log (no moving parts). Will report back after a season's use.