Scott Hersha
Well Known Member
I know there are a lot of GRT EIS users on this forum, so I’m hopeful someone will be able to help me with a problem.
Yesterday I spent the entire afternoon calibrating my float-type resistive fuel senders for my EIS installed in my almost completed RV-6. These are wired to Aux inputs in my EIS according to the install manual through the 4.8v excitation circuitry with 470 ohm resistors that came with the kit. According to the calibration plan you start with a scale factor (AuxSF) of 100, and an offset (AuxOff) of 0 (zero). This whole thing is done with the airplane in a level flight attitude. You are supposed to start with a known quantity of fuel and start draining it out until the reading on the EIS stops going down - which I did. I ended up with a little more than 1/2 gallon remaining in the tank (on both tanks) when the sensor stops indicating lower. This is just for my information and doesn’t affect the rest of the procedure. At the bottom, the left tank read 143, and the right tank read 142. What that number is, I don’t know, but it has to do with measured resistance in the EIS. Then I slowly add fuel until that number stops increasing. On mine both tanks stopped reading at 16 gallons for my 19 gallon tanks, so I know I’ll have to burn off 3 gallons from a full tank before the EIS starts registering fuel quantity - good to know. Both tanks read 197 when the sensor hit the top of the tank.
Now the exercise is to just use the empty and full readings in a formula as directed by the GRT instruction sheets to figure and reset the scale factor (AuxSF) and the offset (AuxOff). My left tank SF/Off was 296/83. My right tank SF/Off was 291/81. This should allow the EIS to register in gallons. I put 10 gallons of fuel in the left tank, and the rest of it, about 9 gallons, in the right tank. The readings I get are 514 on the left (with 10 gallons of fuel in it), and 478 on the right.
This is a math exercise that has gone wrong somehow. So - can I correct this with adjusted SF’s and Offsets, or do I need to do the fuel draining/adding thing again, and if so, how do I do it now, because the GRT process doesn’t seem to be working. This all came together after 4pm yesterday, so no possible help from the GRT team until Monday. I hope I don’t have to go through this whole process again….
Yesterday I spent the entire afternoon calibrating my float-type resistive fuel senders for my EIS installed in my almost completed RV-6. These are wired to Aux inputs in my EIS according to the install manual through the 4.8v excitation circuitry with 470 ohm resistors that came with the kit. According to the calibration plan you start with a scale factor (AuxSF) of 100, and an offset (AuxOff) of 0 (zero). This whole thing is done with the airplane in a level flight attitude. You are supposed to start with a known quantity of fuel and start draining it out until the reading on the EIS stops going down - which I did. I ended up with a little more than 1/2 gallon remaining in the tank (on both tanks) when the sensor stops indicating lower. This is just for my information and doesn’t affect the rest of the procedure. At the bottom, the left tank read 143, and the right tank read 142. What that number is, I don’t know, but it has to do with measured resistance in the EIS. Then I slowly add fuel until that number stops increasing. On mine both tanks stopped reading at 16 gallons for my 19 gallon tanks, so I know I’ll have to burn off 3 gallons from a full tank before the EIS starts registering fuel quantity - good to know. Both tanks read 197 when the sensor hit the top of the tank.
Now the exercise is to just use the empty and full readings in a formula as directed by the GRT instruction sheets to figure and reset the scale factor (AuxSF) and the offset (AuxOff). My left tank SF/Off was 296/83. My right tank SF/Off was 291/81. This should allow the EIS to register in gallons. I put 10 gallons of fuel in the left tank, and the rest of it, about 9 gallons, in the right tank. The readings I get are 514 on the left (with 10 gallons of fuel in it), and 478 on the right.
This is a math exercise that has gone wrong somehow. So - can I correct this with adjusted SF’s and Offsets, or do I need to do the fuel draining/adding thing again, and if so, how do I do it now, because the GRT process doesn’t seem to be working. This all came together after 4pm yesterday, so no possible help from the GRT team until Monday. I hope I don’t have to go through this whole process again….
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