A

ao.frog

Well Known Member
Hi.

I can't get the OAT to show correct values and I think the fault is that mine...?

I have entered two calibration points according the manual which was in effect when I installed the 3500 back in 2007 but the current manual doesn't say anything about entering any calibration points, only to change the shift value until OAT is reading correctly. (Pg 69)

Does this mean that I schould delete my two calibration points, enter 0 in the line for the number of calibration points and just change the shift value until OAT displays correct?
If I recall correctly, an earlier version of the manual said to enter one or two calibration points?

Here's how my OAT calibration screen looks today:




The shiftvalue is set to -6,2 to get the OAT to show correct OAT but regardless of this, the OAT-indication during flight is way too high. For example it indicates -1* C while it's about -10*C outside...

I have also posted the above on the AFS-support forum, but so far no response, so I'm trying here...Any ideas anyone?
 
ao.frog said:
Hi.

Here's how my OAT calibration screen looks today:

Click to expand...

Here is the value on my OAT admin screen:

Shift adjust 0.0
Num Cal points 2

AD_VALUE 100200
32.0 9534
69.0 10148

Don't know the answer to your question, but these are my values
as a reference. My 2 Cal points are much further apart than yours.
 
Questions:

1. Where do you have the OAT sensor mounted?

2. Does it read correct on the ground with the engine off?


NACA vents and the bottom of the fuselage will not work, both places get a lot of heat from the engine.

Your unit was shipped with the following calibrated numbers:

34F 8416
77F 8670



Rob Hickman
Advanced Flight Systems Inc.
 
Last edited:
Thanks...

.... for chiming in Rob.

1) The OAT-sensor is mounted under the left wing just behind the outboard inspection panel.

2) Yes and no: it read approx 0* Celcius when it was about -7*C.
I adjusted the shift value so the OAT showed correct value (-7*C) and with a a shiftvalue of -6,2 (the pic) it displayed correct OAT.

I then went up to fly and in the air it showed approx 0*C again.

It looks to me that the OAT-indication doesn't change much when the actual OAT changes, for example during climbs to higher altitudes or when the OAT changes from day to day.

Is my shiftvalue of -6,2 abnormally big?
 
Alf, you can verify that the probe is working.

You have adjusted it so it is measuring current temp correctly (with the plane on the ground). Now place the probe in a cup of boiling water. If it doesn't measure 100C then the probe must be defective or not calibrated correctly.
Otherwise you are getting some heat effecting it from the engine.

Kent
 
Is the probe wired correctly? It's possible to get the wires switched which will cause it to be wildly inaccurate.
 
Thanks...

.... for the advices guys. I'll try to reset the values to the ones the unit came preset with (the ones Rob wrote about here in this post)
If that doesn't work, I'll try with Tom's values.

I'll also try that boiling water-trick. Thanks Kent!

I'll let you all know how it turns out but it'll be a few weeks or maybe a couple of months, because winter is here now. Here's a pic of the house-thermometer this morning... YUK! (degrees are in Celcius...) so right now it's not quite tempting to go work on the plane.... :D




But what I'll do is to make a note of the AD-value in this temp because then I'll have a nice spread to the other AD-values...
I'll also check our wiring when I'm doing annual in May next year.
 
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