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"limited" EGT and CHT temperatures (Read 780 times)
Jun 5th, 2017 at 3:34am

High_Flyer   Offline
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Hello Dynon,
My setup is full Skyview system with EMS 221, Aerosport IO-375-M1S engine.
I have made my 1st flight yesterday, and noticed that all 4 EGT were not reaching normal temperatures, all very low.
Today I tried to troubleshoot and found out that all 4 EGT do not go over 475F, and all 4 CHT do not go over 375F.
To see this I used a heat gun on the probes. I removed the EGT and the CHT probes and directed the
heat gun at them. Temperatures rises rapidly until reaching 475F for the EGT / 375F for the CHT and suddenly stops at those values, never go higher. My heat gun is set at the max temp of 1200F
I do not understand why this is.
It seems that the probes are somewhow "limited" to these values...
This means no further flight until it is resolved because I will not know if my CHT are too high as the max value displayed is 375F.
HELP PLEASE.
Atteched is a screenshot during yesterday's flight.
 
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Reply #1 - Jun 5th, 2017 at 3:35am

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And further to my 1st post a screenshot made just after landing.
 
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Reply #2 - Jun 5th, 2017 at 8:37am

rvator51   Offline
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I would check all of the configuration settings.  I suspect some are wrong.  do you have your ranges for the sensors set properly?
 
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Reply #3 - Jun 5th, 2017 at 11:45am

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rvator51 wrote on Jun 5th, 2017 at 8:37am:
I would check all of the configuration settings. I suspect some are wrong. do you have your ranges for the sensors set properly?


The config settings can not be changed I think, and I checked the ranges and they are correct. And the ranges even if wrong wouldn't prevent the probes to sense more than 375/475 degrees...
« Last Edit: Jun 5th, 2017 at 11:46am by High_Flyer »  
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Reply #4 - Jun 5th, 2017 at 6:10pm

Dynon Avionics   Offline
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What are you using for the actual CHT and EGT probes? The CHTs must be type J thermocouples, and the EGTs type K. If you're using different sensors, they won't output the voltages SkyView is expecting to see.
 

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Reply #5 - Jun 5th, 2017 at 9:42pm

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Dynon Avionics wrote on Jun 5th, 2017 at 6:10pm:
What are you using for the actual CHT and EGT probes? The CHTs must be type J thermocouples, and the EGTs type K. If you're using different sensors, they won't output the voltages SkyView is expecting to see.


All probes are Dynon, J and K thermocouples.
I ordered all standard Dynon equipment, EMS came with the probes and the EMS wire loom. All I did was shorten the cables from the EMS to the probes (NOT the cables of the probes) as the manual says is allowed.

I tested one EGT probe with a multimeter:
O ohms,
Close to 0 milivolts at ambiant temperature,
22,3 Milivolts with the probe inside the mouth of a heat gun at 1220F.

The nubers on the labels of the probes are: 100405-000 for the EGT, and 100404-000 for the CHT.
The EMS is SV-EMS-220 (see screenshot).
« Last Edit: Jun 6th, 2017 at 1:53am by High_Flyer »  
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Reply #6 - Jun 6th, 2017 at 1:44am

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Screenshot of the sensor input mapping:
 
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Reply #7 - Jun 6th, 2017 at 1:44am

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Screenshot of the sensor debug data:
Please note that at the moment of this screenshot the #2 EGT probe was not installed as I was testing it.
« Last Edit: Jun 6th, 2017 at 1:46am by High_Flyer »  
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Reply #8 - Jun 6th, 2017 at 8:55am

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Can you please send a screen shot of the debug screen scrolled down a bit? There's a section with a bunch of elements like "ColdJ" and "vref+" that would be helpful.
 

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Reply #9 - Jun 7th, 2017 at 3:06am

High_Flyer   Offline
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Dynon Support wrote on Jun 6th, 2017 at 8:55am:
Can you please send a screen shot of the debug screen scrolled down a bit? There's a section with a bunch of elements like "ColdJ" and "vref+" that would be helpful.


Following are ALL the debug pages:
1
 
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Reply #10 - Jun 7th, 2017 at 3:07am

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2
« Last Edit: Jun 7th, 2017 at 3:07am by High_Flyer »  
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Reply #11 - Jun 7th, 2017 at 3:07am

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3
 
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Reply #12 - Jun 7th, 2017 at 3:08am

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4
 
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Reply #13 - Jun 7th, 2017 at 3:08am

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5
 
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Reply #14 - Jun 7th, 2017 at 3:08am

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6
 
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Reply #15 - Jun 7th, 2017 at 3:09am

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7
 
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Reply #16 - Jun 7th, 2017 at 3:09am

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8
 
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Reply #17 - Jun 7th, 2017 at 3:09am

High_Flyer   Offline
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9
 
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Reply #18 - Jun 7th, 2017 at 3:17am

High_Flyer   Offline
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What I've done troubleshooting so far:
- Checked proper probes model installed: OK
- Checked proper EMS installed (EMS 220): OK
- Checked continuity of the wires to the proper EMS pin : OK
- Checked "polarity" of the wires: OK
- Checked Gounds: OK
- Added a ground wire direct from EMS to engine block
- Verified Debug page parameters as told by Dynon support:
Volt Ref around 5V: OK
TC Offest around 0.4V : OK
Clod J around room temp : OK

Ordered other EMS from Finesse max (France Dynon rep), should arrive tomorrow.
If it's not the EMS that's faulty then I really don't know what else to do...
 
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Reply #19 - Jun 7th, 2017 at 8:55am

Dynon Support   Offline
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Alain,
Given the reasonable values from your sensor debug page, it's not likely that the EMS has failed, but it will be interesting to see if that does fix it.

Your limits of CHT and EGT say that the system can no longer read above 20mV. 375F on a J type is 20mV and 475F on a K type is 20mV. So there is a hint there.

Can you please try something else? Heat one of the probes with your heat gun again, but looking at the sensor debug page for that sensor instead of the main screen. What does the line for that sensor show when you do this?

If it is limiting on that page, please un-plug the D37 connector and try again to see if anything on that connector is causing the issue.

Also, have you checked that you have no inputs connected to any of the unused thermocouple inputs? If you were to hook a 5V or 12V signal to one of the unused inputs it could cause this issue.

We'll figure it out!
 

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Reply #20 - Jun 7th, 2017 at 12:47pm

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What do you mean by "have you checked that you have no inputs connected to any of the unused thermocouple inputs" ?

The only things connected to the 25 pin connector are the thermocouples (2 pins per sensor, 16 pins total), nothing else...
 
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Reply #21 - Jun 7th, 2017 at 2:29pm

dlloyd   Offline
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On the sensor setup page there is a minimum and maximum range in addition to the color ranges.  Please post a picture of those pages.
 
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Reply #22 - Jun 7th, 2017 at 2:57pm

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The min and max graphical range won't limit the digital range. That's not the issue.
 

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Reply #23 - Jun 7th, 2017 at 9:26pm

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There are two thermocouple inputs on the D37 connector as well. So an accidental connection here could cause an issue with all thermocouples.

This is why checking with the D37 disconnected would be helpful.
 

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Reply #24 - Jun 8th, 2017 at 12:26pm

High_Flyer   Offline
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Annecy, France

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I got a new EMS today from Finesse Max.
I installed it and did the heat gun test and immediately the temps went above the values of the other EMS.
Then I did an engine run and all is fine.
Tomorrow I will do a flight to confirm that all works as expected.

This is a bit disapointing to see new avionics not working.
I already had similar problem with my VHF. Lucily it was replaced at no cost to me, but it as very frustrating.
Quality control seems to be a bit weak...

Anyway I hope everything will be OK tomorrow durin g the flight, and you will then be able to "close" this topic.
 
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Reply #25 - Jul 14th, 2017 at 8:35am

GregW   Offline
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Can I bend the end of the Skyview EGT sensor?   One of them interferes with a spark plug wire right near the plug.  I would like to bend the last 3/4" where the wires exit.  Maybe bend it 1/2" or so over to the side.   No where close to a kink in the tube, though.  Will I ruin the sensor?
Greg in RV7
 
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Reply #26 - Jul 17th, 2017 at 5:53pm

Dynon Avionics   Offline
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So the way thermocouples are built: there's a junction of two wires/metals at the tip, and the wires go all the way up to that junction. if a wire or the junction breaks, it'll stop working. So there's risk in bending because you may affect the wiring or junction underneath. But if you don't kink it / bend it too far, you may well be just fine. We can't warrant a probe if it fails because of such a modification. So basically, it's a $36 risk, with a good it'll work.
 

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