Outside air temp

[g2omer]

Hi ! My outside air temperature does not work , I made some test and I think the sensor is the problem. Anyone know where I can find another and what type and manufacturer of the sensor... I don't find any info on the sensor... Thanks

 

Francois from Canada !

 

 

[IBob]

[ATTACH=full]46067[/ATTACH] Hi ! My outside air temperature does not work , I made some test and I think the sensor is the problem. Anyone know where I can find another and what type and manufacturer of the sensor... I don't find any info on the sensor... ThanksFrancois from Canada !

Hi Francois, I cannot help you with the type and manufacture.

If that is just one wire coming from it, then it is a resistor of sorts, and relies on the metal it is mounted in (the frame of the aircraft) to complete the circuit.

 

Can I ask what tests you made?

 

Also, there should be some markings on the meter (assuming this goes to a meter) to give an indication of what range of sensor is required.

 

 

[rankamateur]

May also be a faulty selector switch on the dash so check it for continuity in both positions before replacing the sensor.

 

 

[g2omer]

I made a continuity test from both position of the switch, the result : ok. Also I measured voltage to the sensor terminal and I measured voltage...

 

 

[IBob]

I believe the meter is reading the resistance of the sensor, which would be between the wire and the brass body of your unit.

 

I just pulled out the temp stuff in my kit (date Dec2014) but it is different than yours (with no markings either).

 

The resistance of my sensors at 18'C is about 12K Ohms

 

warmed in my hand (36'C?) about 6.7K Ohms

 

but they may or may not be same range as yours: there are many different types.

 

If you are simply switching between 2 sensors to the one meter, then the 2 sensors must have the same range. So maybe measure the resistance of your air box sensor, and that should tell you what the resistance of your outside air sensor should be?

 

(Obviously, the sensors must be disconnected before measuring the resistance.)

 

 

[IBob]

Some sort of lookup table:

 

http://www.veris.com/docs/support/faq/rtd-thermistor_z202030-0n.pdf

 

The (lower) table gives resistance readings vs temperature. So, for instance, it's evident that what I have are 10k thermistors. Which should mean I can replace my sensors, if need be, with 10K thermistors (after finding out what the different 10k types are all about).

 

Maybe you can follow a similar process, Francois.

 

I have a suggestion to add to that: I do a lot of work with different sorts of sensors and transducers (though unfortunately not thermistors, so I am learning here as I go). I would try to find something that is hermetically sealed, especially for an aircraft, as the rise and fall of pressure causes an unsealed device to 'breath' in air with moisture. And that is what seems to kill most of our industrial transducers.

 

 

[SSCBD]

Lick thumb and stick out of window - should drop (rule of thumb (no pun intended)) 2 degrees C per 1000 ft.

 

If thumb gets ice on it descend to warmer air fast as RAA don't like ice.

 

Smile all - but true.