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G3x / GEA24 Brake Temperature

P

PilotjohnS

Well Known Member
Just thinking about how I can use the G3x / GEA 24 to measure brake caliper temperatures.
I have an extra roll of thermocouple wire, and there are two spare inputs to the GEA 24 since I am only using 4 cylinders. Several things come to mind:
1) Do I run the thermocouple wire from the brake caliber all the way to the panel? This runs the risk of picking up interference from the comm antennas and such on the bottom of the airplane. Maybe I run twisted shielded pair to the wheel fairing and a short section of thermo wire to the caliper; this will cause some inaccuracy, but minimize the noise intrusion into the microvolt signal.
2) can the G3x cylinder input be renamed or is there a brake temp input I could tap into?
3)if i use cylinder 5 and 6 inputs, can the yellow and red caution warning temperatures be assigned a different value then the other cylinders? Do I need to reassign the temp limits since the max brake caliper temp is really close to the cylinder temp anyway?
EDIT: i think I will use the extra two temp inputs and not the cylinders 5&6.
So this is a go, I am going to do this. My next step is to measure the inaccuracies using twisted shielded wire verses all thermo wire. Time to Break out the lab equipment.

Just some things to think about before I close up my fuselage wiring.
 
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Pretty sure you will have major issues with copper wire. Never done it, so don't know how bad it will be. Themocouple wire/signals are not that sensitive to noise, unless you put it 1/2" from a 50K volt sparkplug wire or similar.

Larry
 
GP Temperature Input

PilotjohnS said:
Just thinking about how I can use the G3x / GEA 24 to measure brake caliper temperatures.
I have an extra roll of thermocouple wire, and there are two spare inputs to the GEA 24 since I am only using 4 cylinders. Several things come to mind:
1) Do I run the thermocouple wire from the brake caliber all the way to the panel? This runs the risk of picking up interference from the comm antennas and such on the bottom of the airplane. Maybe I run twisted shielded pair to the wheel fairing and a short section of thermo wire to the caliper; this will cause some inaccuracy, but minimize the noise intrusion into the microvolt signal.
2) can the G3x cylinder input be renamed or is there a brake temp input I could tap into?
3)if i use cylinder 5 and 6 inputs, can the yellow and red caution warning temperatures be assigned a different value then the other cylinders? Do I need to reassign the temp limits since the max brake caliper temp is really close to the cylinder temp anyway?
EDIT: i think I will use the extra two temp inputs and not the cylinders 5&6.
So this is a go, I am going to do this. My next step is to measure the inaccuracies using twisted shielded wire verses all thermo wire. Time to Break out the lab equipment.

Just some things to think about before I close up my fuselage wiring.
Click to expand...

You can use GP inputs 6 and 7, set to Custom Temp 1 (Type K Thermocouple) and then assign them a user configurable name. Using CHT inputs would probably not result in a very favorable UI. There is no way to assign different gauge ranges to any individual cylinder.

As you mention, it is best practice to use thermocouple wire for this type of installation. If venturing off-label so to speak, make sure to locate any wire splices in the same general location and exposed to the same ambient temperature for both the hi and lo wires to introduce the least amount of error into the measurement.

Thanks,

Justin
 
Thanks for Response

So you suggested I use GP inputs 6 and 7, and I see in the manual I think I can make a custom “gauge” for that with two pointers. That seems like the preferred method. Also, i can run the thermo wire now and curl it up until I get the gear on. If I have a noise issue, i could wrap the thermo wire with aluminum tape. But remembering my race car days, I dont recall ever have an issue with long runs of thermo wire, so maybe noise wont be a problem.

Thanks for the responses, I will add to this thread as it comes together.

Time to run two thermo wires from the panel to the spar, gosh I hope I am done running wires; I really want to close up the lower forward fuselage and move onto the panel and engine install.
 
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g3xpert said:
You can use GP inputs 6 and 7, set to Custom Temp 1 (Type K Thermocouple) and then assign them a user configurable name. Using CHT inputs would probably not result in a very favorable UI. There is no way to assign different gauge ranges to any individual cylinder.

As you mention, it is best practice to use thermocouple wire for this type of installation. If venturing off-label so to speak, make sure to locate any wire splices in the same general location and exposed to the same ambient temperature for both the hi and lo wires to introduce the least amount of error into the measurement.

Thanks,

Justin
Click to expand...

Justin,
So I guess I need to add a 100K ohm resistor from the GP6 and 7 Low inputs to ground? is that correct? since my thermocouple will be epoxy-ed onto the caliper and shall be isolated, not grounded to the caliper ?
 

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