jcaplins
Well Known Member
For those using the Bus Master for your power and fuel pump switching, I have questions:
(if you're using a Grt EIS4000, even better)
What does your fuel pressure switch circuit look like? what is the input voltage, and fixed resister?
Here is what it should looks like for the GRT EIS to read fuel pressure, but I'm not sure 4.8V is OK for use with the Bus Master:
http://www.grtavionics.com/documents/EIS/VDO 80 and 150 Pressure Sender Aux Input.pdf
I believe I need to read about 2.5V (somewhere between 2 and 3V) for the Bus Manager to work properly at the switching point.
Setup according to the GRT document above, I measure:
(10 ohms, no power)
0psi = 0.136V (fuel pumps off)
35psi = 1.2V (calculated 100 ohms)
41psi = 1.36V (calculated 120 ohms)
Calculating with 12V instead of 4.8:
0psi = (10 ohms) = .385V
35psi = (100 ohms) = 2.99V
40psi = (120 ohms) = 3.85V
This seems like what I need, but that would mean I can not use the same pressure sensor with the GRT and the Bus Manager.
Anyone else have this issue?
Thanks. Happy Holidays.
(if you're using a Grt EIS4000, even better)
What does your fuel pressure switch circuit look like? what is the input voltage, and fixed resister?
Here is what it should looks like for the GRT EIS to read fuel pressure, but I'm not sure 4.8V is OK for use with the Bus Master:
http://www.grtavionics.com/documents/EIS/VDO 80 and 150 Pressure Sender Aux Input.pdf
I believe I need to read about 2.5V (somewhere between 2 and 3V) for the Bus Manager to work properly at the switching point.
Setup according to the GRT document above, I measure:
(10 ohms, no power)
0psi = 0.136V (fuel pumps off)
35psi = 1.2V (calculated 100 ohms)
41psi = 1.36V (calculated 120 ohms)
Calculating with 12V instead of 4.8:
0psi = (10 ohms) = .385V
35psi = (100 ohms) = 2.99V
40psi = (120 ohms) = 3.85V
This seems like what I need, but that would mean I can not use the same pressure sensor with the GRT and the Bus Manager.
Anyone else have this issue?
Thanks. Happy Holidays.