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Are dual fuel gauges possible using Vans and Dynon

C

cxb003

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Is tying the fuel senders together with Dynon SV-EMS-220/Skyview and Vans fuel gauges possible? Basically, allowing two separate systems to monitor fuel quantity.

There is an old forum link below, from 2008 talking about trying to use two fuel gauges but the information is limited without technical instructions.

https://vansairforce.net/community/archive/index.php/t-33049.html

Was anybody able to successfully use both the Vans fuel gauges, as well has having the fuel reading show correctly in the skyview? My airplane uses the float type fuel senders.

Thanks
 
I haven't found a simple way of doing it ...

Using the standard resistance sensors the gauge (or EFIS) sends the operating voltage through a variable resistor to ground to measure the fuel quantity. Connecting 2 "gauges" to one resistor will not work as neither gauge will read correctly and one may be damaged, depending on what voltage they run at. Standard gauges run at 12v, some EFIS run at 5v.

Using an Arduino, or something similar, it is possible to generate two independent outputs proportional to the fuel sensor. But that is a complicated way of doing it. I would like to do something passively but haven't yet figured how to do so.

If you figure it out let me know!!
 
I use both the Van's fuel senders/gauges and the fuel computer (I use the SV-EMS-220 with an Advanced Flight EFIS) and have found them to be both accurate and in very close agreement with each other. I find the fuel computer to be most accurate and I only look at the gauge portion of the EFIS because it happens to be right there in the same lower left hand corner of the EFIS.
 
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MacCool said:
I use both the Van's fuel senders/gauges and the fuel computer (I use the SV-EMS-220 with an Advanced Flight EFIS) and have found them to be both accurate and in very close agreement with each other. I find the fuel computer to be most accurate and I only look at the gauge portion of the EFIS because it happens to be right there in the same lower left hand corner of the EFIS.
Click to expand...

Are your fuel senders actually connected to the SV-EMS-220 using pins 19/20, in addition to the Vans gauges or are you just using the fuel computer as an estimated remaining counter.
 
MacCool said:
I use both the Van's fuel senders/gauges and the fuel computer (I use the SV-EMS-220 with an Advanced Flight EFIS) and have found them to be both accurate and in very close agreement with each other. I find the fuel computer to be most accurate and I only look at the gauge portion of the EFIS because it happens to be right there in the same lower left hand corner of the EFIS.
Click to expand...

Yes, that's my thoughts. Do you have the Van's gauges and the fuel quantity indication on the EFIS? Did you just connect the gauges and the SV-EMS-220 to the tank senders? Pins 20 & 21 on the 220?
 
ok, the basics. the vans sender is simply a volt meter. 12v is applied to the gauge and the sender is the second leg of a simple voltage divider. i have never put a meter to it to find out what the voltages are for full vs empty, but it will be somewhere between 0 and 12v.
the dynon system uses a 5v bus for input/output. however, the system can handle 12v on the input with out any problems per the manual. but the voltage that the input will be based on is 0 to 5v so, using the sender as input for the dynon and the vans gauge will work, however, it may or may not be linear on the dynon as the input will max out at 5v so if the vans guage is above 5v for a given level, the dynon level will stop at the 5v level. so it will probably be somewhat accurate over part of the range.

a simple voltage divider could be used on the input to the dynon to get the range of the sender into the 0 to 5v range to get a linear response for the dynon.
 
It’s an interesting problem. The fuel gauge/sender combination is designed in a way that minimizes the effect of buss voltage variation. It is not a typical shunt/voltmeter/ammeter circuit.

https://www.theengineerspost.com/wp...tric-fuel-gauge-1.png?ezimgfmt=ng:webp/ngcb19

The voltage seen at the sender will be proportional to fuel level but will not be 0-12v. The EFIS is setup to measure a resistance between 33-240 ohms. A variation of the circuit below could be used to convert the voltage seen at the fuel gauge input to resistance to connect to the EFIS but doing so spoils the accuracy of the EFIS fuel level measurement which is a shame because they are very accurate. Your EFIS levels would vary as much as 20 percent between engine off and running. The added complexity doesn’t seem like it’s worth it.

https://i.stack.imgur.com/R0NDW.png
 
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Dynon dual fuel guages with Vans

This is done using two double throw double pole switches with an adjustable resister. The adjustable resister is used to set a fuel quantity that would appear obvious if you forgot and were using Vans gauges with the switch in the wrong position. For example, when I am using Dynon gauges, Vans gauges are set to read almost full and vice versa when using Vans gauges. If I lose my one HDX display, I have a G-5 and fuel gauges. It’s always nice to know how much fuel I have in the tank I'm using. Works like a charm and it also helps for confirming accurate readings. I find my basic Vans gauges are more accurate than the HDX gauges for determining the fullest tank.
 
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