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Fuel gauges fuses

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chris_sinfield(at)yahoo.c
Guest

Posted: Thu Apr 12, 2012 11:49 pm Post subject: Fuel gauges fuses

Hi all

I have searched around but cannot find where it said what fuse size to use with the standard zenith supplied senders and be gauges. I would hate to not have the right size and cause a short in the tank. 

Chris

Zodiac xlb

psm(at)att.net
Guest

Posted: Fri Apr 13, 2012 12:43 am Post subject: Fuel gauges fuses

Hi Chris,



I'm not sure I put a fuse in that whole circuit.  I do have a fuse in 

the Dynon unit that acts as the gauge.



The current expected in a fuel sender circuit should be a maximum of 12V 

/ 100 Ohms  or .120 amps.  This suggests a 1 amp fuse or a little bit 

larger if you want one.  The display unit should not use an appreciable 

amount of current.



It doesn't hurt to have a fuse that is a lot larger than your 

calculation shows.  The fuse is not a regulator.  That means it doesn't 

adjust the current.  It just blows if the current is a lot higher than 

it should be.  A dead short will rise in current very quickly until 

either the fuse or the wiring melts.  So the functional difference 

between a one amp fuse and a 10 amp fuse is trivial.



Have fun,



Paul

XL nearing end of phase I testing.



On 4/13/2012 12:46 AM, Chris Sinfield wrote:

 	  Quote: 	
		   



 Hi all

 I have searched around but cannot find where it said what fuse size to use with the standard zenith supplied senders and be gauges. I would hate to not have the right size and cause a short in the tank.

 Chris

 Zodiac xlb

pmaxpmax(at)hotmail.com
Guest

Posted: Fri Apr 13, 2012 10:23 am Post subject: Fuel gauges fuses

The fuel gauges I have work on resistance.  I didn't include any fuses in the lines to the senders, if that's what you mean. 



Phil



On Apr 13, 2012, at 3:56 AM, "Chris Sinfield" <chris_sinfield(at)yahoo.com> wrote:



 	  Quote: 	
		   

 

 Hi all

 I have searched around but cannot find where it said what fuse size to use with the standard zenith supplied senders and be gauges. I would hate to not have the right size and cause a short in the tank. 

 Chris

 Zodiac xlb

Brad(at)ocbis.com
Guest

Posted: Fri Apr 13, 2012 10:33 am Post subject: Fuel gauges fuses

Chris -



What gauges are you using? The ones that came with my kit work on resistance

only, no power. Just a ground and signal wire, no fuse required.



Thanks - Brad



Brad Rawls

Orange County Brokerage

17782 E. 17th St. #206

Tustin, CA 92780



714-550-0159 voice / 714-550-0869 fax / Brad(at)ocbis.com

--

BARRY CHECK 6

Joined: 15 Mar 2011
Posts: 738

Posted: Fri Apr 13, 2012 12:27 pm Post subject: Fuel gauges fuses

Brad:



There HAS TO BE some power to the system for it to work.  No power in = no power out.

There should be some protective device in the system - A Fuse or a Circuit Breaker (CB).

There maybe a very, very small current draw but that is ONLY when the circuit is working correctly.  Short out the circuit and the current becomes infinite.  Basic circuit deign tells one that circuit protection is for Protection of the Wire; Not the device.  Go recheck your circuit and if you do not have circuit protection Put One In!

 



Now Chris.  You can chose the fuse / CB size by knowing the current draw of the item.  Just install a handheld DMM in SERIES (READING CURRENT) with the device and you will know how much it draws.  If it is in the mili-amp range the easy way to go would be a fuse.  It it is one (1) amp or more use a CB.   What size wire are you using?  I hope no one out there is using Radio Shack wire!  Remember Flight 800.

 



Electronics is a new and different field than pop-rivets and wrench swinging.  If you have any questions I will be very happy to help.

Electrical Engineer & Mechanical Engineer

 

Barry

On Fri, Apr 13, 2012 at 2:35 PM, Brad Rawls <Brad(at)ocbis.com (Brad(at)ocbis.com)> wrote:

 [quote]--> Zenith-List message posted by: "Brad Rawls" <Brad(at)ocbis.com (Brad(at)ocbis.com)>

  

 Chris -

 

 What gauges are you using? The ones that came with my kit work on resistance

 only, no power. Just a ground and signal wire, no fuse required.

 

 Thanks - Brad

 

 Brad Rawls

 Orange County Brokerage

 17782 E. 17th St. #206

 Tustin, CA 92780

 

 Brad(at)ocbis.com (Brad(at)ocbis.com)

 

 

 --

Brad(at)ocbis.com
Guest

Posted: Fri Apr 13, 2012 2:03 pm Post subject: Fuel gauges fuses

The power is at the gauge, not the sender wire from the tank. The float in the tank varies the resistance to ground which reads on gauge in the cockpit. No power to the tank. 

 

Thanks - Brad

 

Brad Rawls

Orange County Brokerage

17782 E. 17th St. #206

Tustin, CA 92780

 

714-550-0159 voice / 714-550-0869 fax / Brad(at)ocbis.com

 

From: owner-zenith-list-server(at)matronics.com [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of FLYaDIVE

Sent: Friday, April 13, 2012 1:26 PM

To: zenith-list(at)matronics.com

Subject: Re: Fuel gauges fuses



 

Brad:

 



There HAS TO BE some power to the system for it to work.  No power in = no power out.



There should be some protective device in the system - A Fuse or a Circuit Breaker (CB).



There maybe a very, very small current draw but that is ONLY when the circuit is working correctly.  Short out the circuit and the current becomes infinite.  Basic circuit deign tells one that circuit protection is for Protection of the Wire; Not the device.  Go recheck your circuit and if you do not have circuit protection Put One In!



 



Now Chris.  You can chose the fuse / CB size by knowing the current draw of the item.  Just install a handheld DMM in SERIES (READING CURRENT) with the device and you will know how much it draws.  If it is in the mili-amp range the easy way to go would be a fuse.  It it is one (1) amp or more use a CB.   What size wire are you using?  I hope no one out there is using Radio Shack wire!  Remember Flight 800.



 



Electronics is a new and different field than pop-rivets and wrench swinging.  If you have any questions I will be very happy to help.



Electrical Engineer & Mechanical Engineer

 



Barry



 



 



 



 

On Fri, Apr 13, 2012 at 2:35 PM, Brad Rawls <Brad(at)ocbis.com (Brad(at)ocbis.com)> wrote:

--> Zenith-List message posted by: "Brad Rawls" <Brad(at)ocbis.com (Brad(at)ocbis.com)>



Chris -



What gauges are you using? The ones that came with my kit work on resistance

only, no power. Just a ground and signal wire, no fuse required.



Thanks - Brad



Brad Rawls

Orange County Brokerage

17782 E. 17th St. #206

Tustin, CA 92780



Brad(at)ocbis.com (Brad(at)ocbis.com)

--

craig(at)craigandjean.com
Guest

Posted: Fri Apr 13, 2012 2:20 pm Post subject: Fuel gauges fuses

In normal operation the resistive sender moves the slider to ground (the same as if you shorted the lead from the gauge to ground). Current is limited to tens of milliamps by the resistance of the gauge. So go ahead and add a fuse but it will never blow unless the gauge malfunctions (and in that case the fuse on the power lead to the gauge would blow). The Volkswagen the sender came out of didn’t fuse this lead. If you want to be consistent you should also add fuses to every other resistive sender that references to ground: oil temp, oil pressure, water temp, etc.

 

-- Craig

  [quote][b]

jaybannist(at)cs.com
Guest

Posted: Fri Apr 13, 2012 2:36 pm Post subject: Fuel gauges fuses

Anyone who thinks you can measure a resistance without a current needs to review basic electronics.  The basic Ohm's law is: voltage equals current times resistance.  Therefore resistance equals voltage divided by current. If there is a voltage present, but current is zero, then resistance is zero and can not be measured.  It will always be zero until there is a current and it can be measured.  Any device to measure resistance must have a current and a voltage must be present to have a current.  Even a simple ohmmeter uses a small current to measure the resistance of a resistor.  If this were not the case, your fuel gauge would read the fuel level with the power turned off.  That being said, the electrical part of the sender that Zenith supplies is totally outside the fuel tank.   Even in the case of an electrical short, no electricity touches the fuel.

 

 Jay

  

     

  

     

  

    --

pmaxpmax(at)HOTMAIL.COM
Guest

Posted: Fri Apr 13, 2012 2:48 pm Post subject: Fuel gauges fuses

With all due respect, anyone who thinks there is a need for a fuse on the Zenith supplied resistance type fuel senders is over-thinking it.  I suggest you move on to other things to work on. 



Phil Maxson

601XL-B/Corvair

Northwest New Jersey

BARRY CHECK 6

Joined: 15 Mar 2011
Posts: 738

Posted: Fri Apr 13, 2012 2:49 pm Post subject: Fuel gauges fuses

Brad:



The power maybe applied at the gauge.  BUT!  There MUST be power to the resistor of the sending unit.

Brad, your conception of how this works is wrong.  

 Pull out the schematic and where ever you see a wire there MUST be voltage in it.   Other wise why even use a wire!  Use a 2x4 instead.  

Brad, Guys, Anybody - Can you direct me to an online schematic of the circuit?  I'll break it down for all.

 



Barry



On Fri, Apr 13, 2012 at 6:05 PM, Brad Rawls <Brad(at)ocbis.com (Brad(at)ocbis.com)> wrote:

 [quote]

 The power is at the gauge, not the sender wire from the tank. The float in the tank varies the resistance to ground which reads on gauge in the cockpit. No power to the tank.  

 

Thanks - Brad

  

Brad Rawls

Orange County Brokerage

17782 E. 17th St. #206 

Tustin, CA 92780

 

Brad(at)ocbis.com (Brad(at)ocbis.com) 

 



From: owner-zenith-list-server(at)matronics.com (owner-zenith-list-server(at)matronics.com) [mailto:owner-zenith-list-server(at)matronics.com (owner-zenith-list-server(at)matronics.com)] On Behalf Of FLYaDIVE

 Sent: Friday, April 13, 2012 1:26 PM

To: zenith-list(at)matronics.com (zenith-list(at)matronics.com)

Subject: Re: Fuel gauges fuses 

 

Brad:

 



There HAS TO BE some power to the system for it to work.  No power in = no power out. 



There should be some protective device in the system - A Fuse or a Circuit Breaker (CB).



There maybe a very, very small current draw but that is ONLY when the circuit is working correctly.  Short out the circuit and the current becomes infinite.  Basic circuit deign tells one that circuit protection is for Protection of the Wire; Not the device.  Go recheck your circuit and if you do not have circuit protection Put One In! 



 



Now Chris.  You can chose the fuse / CB size by knowing the current draw of the item.  Just install a handheld DMM in SERIES (READING CURRENT) with the device and you will know how much it draws.  If it is in the mili-amp range the easy way to go would be a fuse.  It it is one (1) amp or more use a CB.   What size wire are you using?  I hope no one out there is using Radio Shack wire!  Remember Flight 800. 



 



Electronics is a new and different field than pop-rivets and wrench swinging.  If you have any questions I will be very happy to help. 



Electrical Engineer & Mechanical Engineer

 



Barry



  



 



 



  



On Fri, Apr 13, 2012 at 2:35 PM, Brad Rawls <Brad(at)ocbis.com (Brad(at)ocbis.com)> wrote:

 

--> Zenith-List message posted by: "Brad Rawls" <Brad(at)ocbis.com (Brad(at)ocbis.com)>



Chris -



What gauges are you using? The ones that came with my kit work on resistance

 only, no power. Just a ground and signal wire, no fuse required.



Thanks - Brad



Brad Rawls

Orange County Brokerage

17782 E. 17th St. #206

Tustin, CA 92780



Brad(at)ocbis.com (Brad(at)ocbis.com)

 



--

BARRY CHECK 6

Joined: 15 Mar 2011
Posts: 738

Posted: Fri Apr 13, 2012 2:52 pm Post subject: Fuel gauges fuses

Thank You Jay!You are 100% correct.

Your explanation of the variable resistor being outside of the tank explains why Brad is confused.

Barry



 On Fri, Apr 13, 2012 at 6:36 PM, Jay Bannister <jaybannist(at)cs.com (jaybannist(at)cs.com)> wrote:

[quote]    Anyone who thinks you can measure a resistance without a current needs to review basic electronics.  The basic Ohm's law is: voltage equals current times resistance.  Therefore resistance equals voltage divided by current. If there is a voltage present, but current is zero, then resistance is zero and can not be measured.  It will always be zero until there is a current and it can be measured.  Any device to measure resistance must have a current and a voltage must be present to have a current.  Even a simple ohmmeter uses a small current to measure the resistance of a resistor.  If this were not the case, your fuel gauge would read the fuel level with the power turned off.  That being said, the electrical part of the sender that Zenith supplies is totally outside the fuel tank.   Even in the case of an electrical short, no electricity touches the fuel.

  

 Jay

  

     

  

     

  

    

--

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Fri Apr 13, 2012 6:33 pm Post subject: Fuel gauges fuses

Fuses exist to protect the wires connecting your electrical circuits, not the devices connected to those wires. The fuse should be sized according to the size of the smallest wire in your circuit. You will probably have several gauges supplied by the same circuit, that circuit will be protected by a single fuse. The fuse should blow (or the breaker should trip) before the wires can overheat. I am using one amp breakers in my gauge circuits.



Gauges generally are very high resistance circuits, they draw very little current. A typical gauge is a coil made of very fine wire that generates a small magnetic field to move a needle. When a gauge fails, it fails by fusing the fine wire that drives the needle or by frying the electronics inside the gauge housing. This will open the circuit. 



The sender in a fuel gauge circuit is on the grounded side of the gauge, it usually is a resister that varies from 0 to a few hundred Ohms. If it shorts out it simply drives the needle to full scale. The sender can tolerate a whole lot more current than the gauge can. Resistive fuel senders have been used for decades in gasoline powered vehicles with no safety issues. Even if you could get a short in the tank, a fuse would blow or the wire would melt down before it would cause a problem, unless you are burning jet fuel. The fuel-air mixture inside a gasoline tank is too rich to burn, not enough oxygen. On the other hand, the fuel air mixture in a diesel tank is too lean to burn, not enough vapor. Kerosine (jet fuel) is somewhere in between.



On Apr 13, 2012, at 3:46 AM, Chris Sinfield wrote:



 	  Quote: 	
		   

 

 Hi all

 I have searched around but cannot find where it said what fuse size to use with the standard zenith supplied senders and be gauges. I would hate to not have the right size and cause a short in the tank. 

 Chris

 Zodiac xlb


	


-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

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