Electrical Gauges Over Reading

A place to exchanges questions and ideas of a technical / procedural nature. Go ahead, try to stomp us !
EchoTangoOscar
Bilge Dweller
Posts: 2
Joined: Sun Jun 27, 2010 11:13 pm

Electrical Gauges Over Reading

Postby EchoTangoOscar » Mon Jun 28, 2010 12:06 am

Hi

I have a Novurania on board the yacht that I work on and all of the gauges are over reading....

CW Temp
Oil Press
Fuel Tanks
etc

One I could understand a failure in the sender unit - but all of them has to be an electrical problem - short, leakage...

Anybody help with this one?

Cheers

ETO

Martin - great site - keep up the good work - i also run a forum called http://www.yachtietotty.com which is aimed more at the white boat enigneers but though that some of you that work on the real boats may be able to help us out! (Sorry nicked some of your jokes - but i thought they were worth sharing!)

User avatar
Big Pete
Engineering Mentor
Posts: 813
Joined: Fri Apr 24, 2009 11:18 pm
Currently located: Solihull, England

Re: Electrical Gauges Over Reading

Postby Big Pete » Mon Jun 28, 2010 2:14 am

I am not familiar with this system, but as you say obvious points to look at are Earth/ground faults and is the supply voltage correct?

Another thing is that in many electronic systems, each sensor has to be calibrated to the system when it is installed. Basically you insert the probe into melting ice and tell the unit it is at 0 and then into boiling water and tell the unit it is at 100, and it will calculate all the linear and scalar errors for itself and give correct readings in the future. If this was not done properly when the system was installed, that could be your problem.
I would check the correct set up procedure in the manual and try going through that.
Good luck.

BP
It is always better to ask a stupid question than to do a stupid thing.

User avatar
D Winsor
Superintendent
Posts: 331
Joined: Thu Nov 22, 2007 8:23 am
Currently located: Dartmouth

Re: Electrical Gauges Over Reading

Postby D Winsor » Tue Jun 29, 2010 4:33 am

Most electronic systems like yours use shielded cables between the transducer and the computer or PLC. If there is a break or damage to this shield, possibly around the engine, or poor shield grounding will cause problems like you describe through out the system.
Troubleshooting a problem like this is hard to find and very time consuming.
Here are some places to check
1. Cables around the Engines and generators that may have been damaged by vibration, heat or moisture especially around clamps or where oil or water may have leaked on to the cables
2. Cables and junction boxes on or near generators, electric motors or distribution networks.
3. Navigational aids such as VHF radios, satellite communication equipment and radars. These items have transmitters that been known to cause problems with electronics.
4. Any new equipment that may have been installed in the recent past

Hope this helps
Troubleshooting 101 "Don't over think it - K.I.S.S. it"

User avatar
Big Pete
Engineering Mentor
Posts: 813
Joined: Fri Apr 24, 2009 11:18 pm
Currently located: Solihull, England

Re: Electrical Gauges Over Reading

Postby Big Pete » Tue Jun 29, 2010 11:26 pm

With regard to wiring up these electronic units, the signal cables must be shielded with copper braid on the outside (Not to be confused with armoured!).
To shield the signal the Braid must be properly Earthed, BUT ONLY AT ONE END. The other end of the Braiding should be left insulated. If the Braid is Earthed/Grounded at both ends, current can flow along the braid and interfere with the signal.
This applies to all signal cables, the braid is there to intercept electro magnetic radiation, and Earth it. If both ends are Earthed, current can flow along the braid and this will induce current in the signal cable.
BP
It is always better to ask a stupid question than to do a stupid thing.

EchoTangoOscar
Bilge Dweller
Posts: 2
Joined: Sun Jun 27, 2010 11:13 pm

Re: Electrical Gauges Over Reading

Postby EchoTangoOscar » Wed Jun 30, 2010 12:39 am

Thanks for the pointers gentlemen.


Return to “The Workshop”

Who is online

Users browsing this forum: No registered users and 1 guest