OAT wiring - testing?

Post here for anything that does not fit any of the categories below. Any topic related to MGL and flying welcome.
Forum rules
Please keep your posts friendly and on topic. No politics or discussions of a controversial nature not related to our favorite subject of flying and avionics. Offending posts may be removed or moderated.
Post Reply
Loman
Posts: 7
Joined: Fri Dec 11, 2020 4:50 pm

OAT wiring - testing?

Post by Loman »

I have grafted on the wires of the supplied OAT sensor to the relevant wires of the iBox PWR connector. As I understand it, OAT green goes to iBox black on pin 4 and OAT red goes to iBox green (TMP) on pin 9. I have used solder sleeves, which are new to me

But how to test my work? Should there be connectivity across these pins? Do I need to apply voltage and measure resistance? Perhaps I should leave well enough alone until the iEFIS system is powered up and just see if it works, but it would be more difficult to fix at that stage.

I notice that there are two other cores in the OAT sensor cable, yellow and black, which are just snipped off.
Loman

Arklow, Ireland
Vans RV9 Tailwheel Tip-up. Slow, (very slow) build
O-320, Full MGL system
Airframe complete, currently installing FWF and electrical systems
adamoconnor
Posts: 67
Joined: Mon Aug 31, 2020 2:33 pm

Re: OAT wiring - testing?

Post by adamoconnor »

Loman wrote: Tue Apr 06, 2021 5:12 pm I have grafted on the wires of the supplied OAT sensor to the relevant wires of the iBox PWR connector. As I understand it, OAT green goes to iBox black on pin 4 and OAT red goes to iBox green (TMP) on pin 9. I have used solder sleeves, which are new to me

But how to test my work? Should there be connectivity across these pins? Do I need to apply voltage and measure resistance? Perhaps I should leave well enough alone until the iEFIS system is powered up and just see if it works, but it would be more difficult to fix at that stage.

I notice that there are two other cores in the OAT sensor cable, yellow and black, which are just snipped off.
The temp sensor in the OAT probe is technically a "chip" so it won't be as easy as just using a DMM to check. Rainier might be able to chime in, but as long as the connections are secure and don't move - or otherwise the solder in the sleeve has properly flowed, then you should be perfectly okay.
Adam O'Connor
Michigan Avionics
MGL USA Sales and Support
rainier
Site Admin
Posts: 652
Joined: Fri Aug 28, 2020 7:03 pm

Re: OAT wiring - testing?

Post by rainier »

We use the popular LM335 sensors.
We supply them with a small current and they "drop" a voltage which is dependent on temperature. It is easy to test them as follows:
Voltage drop is linear and proportional to temperature in degrees Kelvin with every degree equal to 0.01V.
0 degrees C is 273 degrees Kelvin = 2.73V (32 degrees F)
30 degrees C is 303 degrees Kelvin = 3.03V (86 degrees F)

The iBOX simply measures the voltage with respect to ground at the RDAC.
DKnezacek
Posts: 3
Joined: Sat Apr 30, 2022 9:34 pm

OAT connecting

Post by DKnezacek »

I am trying to figure out how to connect my OAT probe to my Vega EMS-1. I can't find any reference to doing this in the manual.

I guess it needs to be connected to one of the analog inputs? That would be the Orange, Green, Gray, or Red/White striped wires?

The other wire would be connected to ground, I'm guessing? Does it need to be connected directly to the engine, or can it be connected to a ground bus?

The probe has one black and one red wire. Does it matter which one is connected to the EMS-1?

Thanks,

Dan Knezacek
sparxfly
Posts: 69
Joined: Mon Aug 31, 2020 5:57 pm
Location: Waikato, NZ
Contact:

Re: OAT wiring - testing?

Post by sparxfly »

Black to ground, red to input, pullup resisdtor ON, set sensor as LM335 type.
Stuart
NZ MGL dealer
adamoconnor
Posts: 67
Joined: Mon Aug 31, 2020 2:33 pm

Re: OAT wiring - testing?

Post by adamoconnor »

sparxfly wrote: Sun May 08, 2022 8:11 pm Black to ground, red to input, pullup resisdtor ON, set sensor as LM335 type.
Sometimes Green is ground too.
Adam O'Connor
Michigan Avionics
MGL USA Sales and Support
DKnezacek
Posts: 3
Joined: Sat Apr 30, 2022 9:34 pm

Re: OAT wiring - testing?

Post by DKnezacek »

So the pullup resistor goes from the input to 5v, or 12v?

Is the resistor directional? There were 3 or 4 resistors that came in the package, are they all the same?

Dan
Post Reply