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OAT problem

Postby pilotmansam » Thu Oct 04, 2018 1:03 pm

I have installed the OAT probe input to my Sport EX, but I have not been able to get it working reliably. I am going to order another probe and just start over with the wiring. Is there a way to just disable the TAS, and Wind calculations until I get the new probe? Or, to ask the question another way, What does the EFIS do with these calculations when the OAT is invalid (i.e. -50 deg F).
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Re: OAT problem

Postby GRT_Jeff » Fri Oct 05, 2018 1:53 am

If you set the "Outside Air Temperature Source" setting to "Auto" and the input reads below -40 deg F, then the EFIS will compute OAT from a standard atmosphere profile. You can turn off the wind display and disable TAS data boxes on the PFD in SET MENU, Primary Flight Display.

You can check the OAT probe by measuring its resistance when not connected on either end. It should read somewhere between 32.6k ohm at 32 F and 5.3k ohm at 104 F.

You can check the OAT input on the EX by connecting it through a 10k resistor to ground. It should read about 77 deg F.
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Re: OAT problem

Postby pilotmansam » Fri Oct 05, 2018 1:00 pm

OK. Thanks Jeff. Always prompt with answers. So, I do not have an EIS, so the OAT is connected directly to the EFIS. When I select "auto" for the OAT source it returns a blank - no reading. So, when it is doing this is it trying to compute OAT from the standard lapse rate? BTW, I am having a great time with my Sport EX. None of this really interferes with my flying. I am just trying to understand all I can about how all this works. Sometimes when something does not work just right is when you actually learn things.
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Re: OAT problem

Postby GRT_Jeff » Mon Oct 08, 2018 6:25 pm

Yes, the EFIS will show a blank or dashed OAT when it doesn't have a real measurement. For TAS and wind and any other calculations the EFIS will use the standard value.
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