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GRT EIS with Van's fuel level sensors

jgbmo

Active Member
I built my RV7 using the Van's resistive fuel level sending units, which are connected to a GRT Avionics EIS 4000. GRT has a set of formulas that you are supposed to use for calculating two parameters: scale factor and offset. I came up with values for those parameters, entered them into the EIS, and got bogus results. I then found an on-line calculator on the GRT site, used it, came up with totally different results (which I entered into the EIS), and again got bogus results.

If any of you have mated the GRT Avionics EIS 4000 to Van's fuel level sending units, please let me know what values you used for scale factor and offset (assuming they worked).

Thank you!
 
I just did this, it had me scratching my head a lot. I ended up with AUX SF 39 and AUX OFF 105. Your numbers will be different but similar, I used the online calculator. Can you post what your EIS empty and EIS full readings are?
 
The Van's float gauges show full at 15 gal (on my RV-7A) so make sure you use that number for 'full' in the formula. Anything above 15 gal is not shown on the EIS because the floats can't report it.
I don't know the numbers I used (13 years ago), but can check next time I'm at the airport.
 
I recently replaced mine, numbers from my existing L no way would work for new sender R. What I learned from the process was rocking things a little initially to make sure my first change was solid eg: bottom/ lowest reading, then as I added fuel one gallon at a time, a little rocking again and wait. I had someone sit in plane to monitor the changes.

I found a pic of my notes during the process, maybe it will help.
 

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1. You didn’t mention it but I presume you installed the 470 ohm bias resistor between the sensor and the 4.8 volt power? Test with a voltmeter on the sensor.
2. Yes, the floats sometimes stick a bit. Normal vibration in flight keeps them unstuck. On the ground knock on the end rib before each measurement.
 
Here’s my results for my RV4:

Left Tank: AUX SF 104
AUX OFF 293

Right Tank: AUX SF 107
AUX OFF 313

Left tank is a little more accurate, but not until it is below about 10 gallons (16 gallon tank). When left tank says zero, I usually have a little left (<1gal). When the right tank says zero, I have about 2 - 2.5 gallons left.
No……. I’ve never run a tank dry. I have very accurate dip sticks that I’ve made, and my totalizer, based on FF calculation in my EFIS is usually within .1 - .2 gallons.
 
BTW, if you are running the EIS into a GRT EFIS, you can build up a calibration table in the EFIS that will make these gauges very accurate.
 
I have another type of fuel problem where my gauges read correctly on the ground. On takeoff roll they go to zero and on landing roll the gauges read accurately again. I have the EIS 4000 and the GRT EFIS. So in flight they read zero, but the fuel used is accurate. Any ideas? This condition has been like this ever since I bought this already flying RV9A. george
 
I also have the EIS 4000 and factory Vans gauges.. I didn’t know there was a way to connect the two.. I fuel it up, and update the “Tank Capacity” in the EIS, and the totalizer tells me how much is left. What does it do if you connect the fuel gauges into the system? I don’t see anything about this in the manual.
 
just did it recently and used calculations given in the installation manual
that was very accurate didnt even need to use EFIS corrections table
couple of thinks are important here
1)empty and full numbers for calculations must betaken with aircraft in cruise
attitude and SF and OFS set to default values
2) pullup resistors are different for V and S units of EIS check software version
i think 301 and 470 ohm
3) OFS must be an odd number
 
I also have the EIS 4000 and factory Vans gauges.. I didn’t know there was a way to connect the two.. I fuel it up, and update the “Tank Capacity” in the EIS, and the totalizer tells me how much is left. What does it do if you connect the fuel gauges into the system? I don’t see anything about this in the manual.

What are you using for an EFIS? If it is a GRT then everything in the EIS feeds directly to the EFIS. george
 
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