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Engine gage wiring

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DanM

Joined: 16 Nov 2006
Posts: 64
Location: Kingsburg, Calif.

Posted: Wed Feb 21, 2007 7:14 am Post subject: Engine gage wiring

I installed a UMA oil pressure gage, PN 4-210-080 and a oil temp gage, PN 12-200-250f in my Kitfox IV with a Jabiru 2200 engine. When I open the master switch (split rocker), the gages have readings of approximately 25 psi oil pressure and 120 degree oil temp. The engine hasn't been started yet (new aircraft), so there must be something wrong with the wiring or the sending units supplied with the engine. I check the gage wiring and looks to be correct. I suspect either a wiring issue or a sending unit issue. I you can help me out, it would be appreciated.



Thanks in advance

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_________________
Dan Mc Intyre
Kitfox IV
Jabiru 2200 SN 1311 , 59.7 hours
Sensenich 62x46
N443DM

mlas(at)cox.net
Guest

Posted: Wed Feb 21, 2007 8:06 am Post subject: Engine gage wiring

Dan,



Check all of your grounds.  Make sure the engine is grounded to the

airframe.  Make sure that the instrument is grounded to the main ground

(airframe)or ground bus.  Make sure you have a large enough ground from

the engine to the airframe.



Just my thoughts,



Mike Larkin



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nuckollsr(at)cox.net
Guest

Posted: Wed Feb 21, 2007 9:22 am Post subject: Engine gage wiring

At 07:14 AM 2/21/2007 -0800, you wrote:



 	  Quote: 	
		  



I installed a UMA oil pressure gage, PN 4-210-080 and a oil temp gage, PN 

12-200-250f in my Kitfox IV with a Jabiru 2200 engine. When I open the 

master switch (split rocker), the gages have readings of approximately 25 

psi oil pressure and 120 degree oil temp. The engine hasn't been started 

yet (new aircraft), so there must be something wrong with the wiring or 

the sending units supplied with the engine. I check the gage wiring and 

looks to be correct. I suspect either a wiring issue or a sending unit 

issue. I you can help me out, it would be appreciated.



Thanks in advance


	


     Without knowing details of the internal

     workings for these instruments, I'll offer

     the following hypothesis to explain what

     you're observing:



     The earliest PRECISION (meaning stable and

     repeatable) instruments were crafted from a

     coil of wire suspended in a magnetic field

     where a current impressed on the coil would

     force rotation against a spring and move a

     pointer upscale. This is known as the

     D'Arsonval meter movement.



http://www.triquartz.co.uk/ammeter.html



     Similar devices had moving magnets held at

     "zero" by a spring and suspended in a single

     fixed coil.



     Both of these technologies feature a

     return spring that causes the instrument

     to assume a familiar and expected

     "zero" reading when powered down.



     Modern instruments have worked past

     some of the manufacturing problems with

     legacy designs. A very popular, robust and

     inexpensive design is also moving magnet.

     But instead of one coil, there are two coils

     at right angles to each other. When the

     two coils are energized, the magnet (free

     to move 360 degrees) will assume alignment

     with the magnetic field generated by the

     two coils.



     This technology allows a designer to produce

     instruments having very small rotational

     arcs . . . up to and including 360 continuous

     degrees without stops. These movements do not

     have or need return springs. Therefore, the

     position assumed by the pointer in a powered

     down condition may be random and unpredictable

     unless the designer takes special pains with

     driving circuitry to make the instrument indicate

     "zero" when powered down.



     Given the popularity of this technology and

     the very reasonable cost to manufacture, I'll

     bet that what you're seeing is the predictable

     behavior of a 4-quadrant, moving magnet movement

     during power down. As long as the instrument is

     reading correctly when powered up, there's

     no reason to be concerned.



     Bob . . .



     For further reading see:

http://www.jewellinstruments.com/pmtheory101.htm



http://www.jewellinstruments.com/pmglossary.htm

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DanM

Joined: 16 Nov 2006
Posts: 64
Location: Kingsburg, Calif.

Posted: Wed Feb 21, 2007 9:52 am Post subject: Re: Engine gage wiring

I ment to say that the gages are at zero with no power applied, when I power up thats when the gages go to the 25psi and 120 degree reading, engine not running. What do you think??? Thanks for the help

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_________________
Dan Mc Intyre
Kitfox IV
Jabiru 2200 SN 1311 , 59.7 hours
Sensenich 62x46
N443DM

Dale Ensing

Joined: 11 Jan 2006
Posts: 571
Location: Aero Plantation Weddington NC

Posted: Wed Feb 21, 2007 10:15 am Post subject: Engine gage wiring

Dan,

I remember getting an obviously erronous number on my oil pressure when 

system was first turn on. Solved the problem by reversing the leads 

connection at the sending unit. The  sending unit had no indication of 

polarity so initial connection was a 50% guess.

Dale Ensing



---

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_________________
Dale Ensing
RV-6A
Aero Plantation
Weddington NC

frank.hinde(at)hp.com
Guest

Posted: Wed Feb 21, 2007 10:19 am Post subject: Engine gage wiring

Either the wrong senders for the guages or a bad ground between the

sender and the guages.



Worng senders happen quite often.



Call the supplier and ask them what the resistnace curve looks like, i.e

get the resistance for say 55F and measure resistance with your

multimeter.



Frank 



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