NTC expected voltage readings (Carb Temp)

[technerdian]

Hi,

I have AUX1 configured as the carb temp channel.

I have a 2-wire NTC probe attached to AUX 1 and to RDAC ground. (https://ie.rs-online.com/web/p/temperat ... s/1241081/) Unfortunately there is no profile given for this probe.

The diagnostics are showing decreasing AUX1 voltage as I warm up the probe. At 12C (room temp) it is showing 4.36V and at 25C it is showing 4.16V. The carb temp widget however, shows 0C regardless.

I have the pull up resistor on (without it the carb heat widget jumps to 208C).

Any ideas? Does anyone know the resistance profile the RDAC expects from a "Standard NTC Probe"?

Thanks,

Gareth.

[rainier]

Standard NTC probe is a oil temperature sender as the ones found in many engines (including Rotax). They are VDO senders or clones. If I remember correctly 100 ohms is 100 degrees C or close to that (writing this from memory so may be a bit out - there is a nice graph in the Rotax technical manuals).

In your case it appears you have a NTC with a very high resistance. It's barely changing the voltage (there is a 1.5KOhm pull up to 5V).

[technerdian]

Thanks Rainier,

I've switched out to a PT100 probe and it appears to be much happier now.

Gareth.

[christoph.glomski]

Hello Technerdian, hello Rainier,

normally Rotax is using NTC Sensors. There is no problem to calibrate the MGL Device with this data. BUT if you have used a FLYDAt as EMS, than there are PT-100 Sensors with another Graph. Im was looking for the sensordata, but there is no chance. MAybe you are able to help.

Grrrtings
Chris

[AkiSuokas]

can be same, or not

Having difficulties to get carb temperature to work properly.
It shows temperatures, but the minimum temperature is 20 deg C!
And for carb temp the interesting temperature is lower, near zero.
Or is the problem with the sensor (picture)?

[Viggenbuilder]

Hi Ranier,
Was this question answered as I have the same question today which I am trying to resolve.
I have the Westach Carb Temp sender as supplied by the local MGL distributor, connected between Aux 1 and RDAC ground.
It is selected to Carb Temp on the screen for my own new indicator graphic , however it shows 0 (Zero degrees) for any value below 20 Degrees ( and works the same for the Simulator as well).
I am trying to get the indication to give the actual probe temp value down to Zero degrees, and start flashing when it gets to 5 Degrees.
Do you have any thoughts or solutions on what I am doing wrong or how to get it to work correctly please.
Richard.

[Viggenbuilder]

The resistance for the 399W westach carb sensor is here.
What is the best settings to use to get down to 0C.

Westech 399W values.jpg (20.02 KiB) Viewed 4267 times

Thanks.

[aelsaadany]

Were you ever able to resolve your issue? I am having the same problem with the Westach where the temperature shows 0°C or 32°F for any value below 20°C or 68°F. It's rather annoying that you wouldn't be able to see a temperature rise when applying carb heat until it reaches 20 degrees.