I've been playing around with my EMS (Engine Monitoring Module) unit, getting all of my sensor inputs finalized for the SV. It does much more than just engine monitoring however, all sensors go through this unit. One goal I had was to add general purpose thermocouple's for the engine compartment and also for the cabin temp. I was a little confused how to go about doing this and posted my question on the Dynon forum with no response. I think I now have it figured out sans any extra help so I thought I would share it with my readers to save you some time.
For the engine compartment, a thermocouple is definitely the way you want to go because of the temp range. You will notice that Dynon uses J-type and K-type thermocouples for CHT and EGT respectively. The main difference you need to know between the two is that they are capable of different temperature ranges. The K-type has a higher temp range, is inexpensive and is generally thought of as a general purpose TC.
The reason for this TC in my setup is to detect an engine fire and provide warning to the cockpit. I plan to mount the sensor near the lower exhaust exit area as that seems to be the logical place for fire exiting the cowl in flight. Early fire detection is paramount to turn off the fuel source and get down safely, many pilots do not realize they are on fire until late in the game.
So, now I know I need a TC for the engine compartment...I could order one from Dynon, but I went hunting on Ebay for something cheaper. I found K-type TC's for $3.50 each with free shipping from China...can't hardly beat that! Even if they turn out to be junk I am only out $10 (I ordered three...one for a spare).
I received them (shown above) and proceeded to hook them up to the designated pins 27/28 and 36/37 on the EMS 37 pin connector. For K-type sensors, the yellow is positive (polarity is important). My sensors, however, had wires that were white w/ red stripe and white w/ black stripe. Turns out the red is positive. I then setup the sensors in the SV EMS setup screen...added widgets to the screen and fired everything up. Bam! Low and behold, I now have cabin temp and engine compartment temp. They seem to be working just fine.
Here is a screenshot showing my two TC's in action. The Cabin temp (74 deg) was high because I was putting the TC in the palm of my hand trying to test it. The 62 deg temp didn't quite match up with my CHT and EGT TC's that showed 64 degs, but I can live with that for $3.50. Also notice all of the indicator "widgets" you can add to your SV (multiple arrows)...it kind of makes an annunciator system not needed. I reduced my panel LED indicators because of this.
From what I can tell from SV installation manual (see above), you can also do cabin temp with one of their OAT temp sensors. It appears these are not actually TC's, but just a thermometer. This would work fine also, but beware Dynon wants $37 for an OAT probe. For me, the TC will suffice I believe...cabin temp is a nice to have, not a must have...time will tell if I have problems with it.
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