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Fuel Pressure Indication setup HXr EFIS

Postby glk0346 » Mon Jan 07, 2019 3:12 am

Is there a different Set-up and configuration for a fuel pressure sender wired directly to a HXr EFIS versus wiring directly to the EFIS as put forth in the VDO Supplemental for the EIS, e.g. scale factor, Aux Off, etc.?

I ask this question because i have a VDO 0-30 psi Pressure Sender wired directly to my HXr via an Analog function and configured as per the supplemental and the Configuration and Set-up Guide for the HX, HS, WS EFISs and pull-up resister ON.

With this configuration, I get 47.4 psi with my system powered up, eng not running. With just the Boost Pump on and or the eng running I get no discernible chg in my reading.

I've reread the HXr Install Manual, the HX, HS, WS Set-up Guide, and delved in depth to the GRT web site with no solution.

Any help and or advice would be greatly appreciated.

George
glk0346
 
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Joined: Wed Jun 06, 2018 3:51 am
Location: Huntsville Executive Airport, Meridianville, AL

Re: Fuel Pressure Indication setup HXr EFIS

Postby Bobturner » Mon Jan 07, 2019 6:06 am

As shown in the EIS - vdo supplement, you need a bias resistor around a few hundred ohms. The internal pull up resistor in the HXr et al is like 10,000 ohms. Try turning off the internal pull up, and supply an external 470 ohm bias resistor off the 5 volt supply, as shown in the supplement.
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Re: Fuel Pressure Indication setup HXr EFIS

Postby glk0346 » Wed Jan 09, 2019 3:01 pm

Thanks, Bob.

I'll have to use a 200 Ohm resistor instead in that normal fuel pressure for an O-320 is 4-6, with 8 being the max.

George
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Posts: 31
Joined: Wed Jun 06, 2018 3:51 am
Location: Huntsville Executive Airport, Meridianville, AL

Re: Fuel Pressure Indication setup HXr EFIS

Postby glk0346 » Sat May 04, 2019 4:46 am

Bob,

This configuration is fine if I'm using the EIS, with the line from the 200 ohm resister feeding voltage to the EIS. But I'm not using the EIS for any of my Analog inputs. I'm using the HXr EFIS Analog configuration with the line from the 200 ohm resister tapped into the HXr EFIS as Analog input No. 4. So the question is

What Scale Factor and Off Set do I use? I do have the pull up resistor turned off and the output set for Integer considering fuel pressure for an O-320 is 0-10.

After many months of working on this instrument panel, I've finally got my RV9A in the air and I must say I'm truly impressed at that HXr and the interfaces with all the other components, Gamin 400W, 1 remote Val Com, one remote Val Nav, a Garmin 330es, and a Tru Trak autopilot.

Any information and or recommendations would be greatly appreciated

George
glk0346
 
Posts: 31
Joined: Wed Jun 06, 2018 3:51 am
Location: Huntsville Executive Airport, Meridianville, AL

Re: Fuel Pressure Indication setup HXr EFIS

Postby glk0346 » Mon May 06, 2019 11:30 pm

Disregard. I got figured out.
glk0346
 
Posts: 31
Joined: Wed Jun 06, 2018 3:51 am
Location: Huntsville Executive Airport, Meridianville, AL

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