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Engine monitor display scramble from EFI sense line EM2 fro

 
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kjashton(at)vnet.net
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PostPosted: Tue Nov 05, 2019 5:24 am    Post subject: Engine monitor display scramble from EFI sense line EM2 fro Reply with quote

Just watching a video the other day about old solder joints that break or crack due to hot/cold cycles or mechanical stress. They are difficult to detect with the eye but I think I would try to touch as many of your joints as possible with a small soldering iron.
-Kent

Quote:
On Nov 5, 2019, at 4:03 AM, Todd Bartrim <bartrim(at)gmail.com> wrote:

I have an issue with my engine monitor display where the display will scramble leaving me with a meaningless display as can be seen in the attached picture
<EM2 display_scrambled.jpg>
The engine Monitor is from Real World Solutions and is the very early first edition EM2 (serial #003). I also have an early edition EC2 (engine ignition and injection controller).
RWS was Tracy Crooks company before he retired, and he still provides some support when he can, however he also is enjoying his retirement offline so is often hard to get a hold of,
so I thought I would pose the question here while awaiting a response so maybe I won't even have to bother him.

So here are the details of the problem. The engine monitor has 36? different parameters that it displays on 8 screens. There are 24 different sensors (pressure, temperature, level) with the remaining being provided through a serial data link from the EC2 along with an EFI sense which is connected to the #1 primary injector output from the EC2. I've determined that it's this last wire that is causing my grief.
This EFI sense is measured for it's pulse width in order to calculate a surprisingly accurate fuel flow, RPM, HP, fuel remaining, MPG (for efficiency). But the noise on this line seems to be the cause of the data scrambling on the display. Simply pressing the cancel button (there are 4 user buttons to control display) will rest and clear the issue.
But here's the weird part. It seems to be related to relative humidity. During hot dry, summer weather this display will rarely scramble, sometimes going up to an hour without an issue. But on cooler humid days I would have to reset it every few minutes which gets a little annoying. However right now as we are not enjoying the cold November rains before winter will arrive with cold dry weather, I'm finding that it is scrambling almost immediately after a reset. This makes no sense to me, but I've observed this pattern enough to be sort of certain that it is not a coincidence... but I could be wrong.
In any event, it matters not whether it is or isn't triggered more by the humidity, but what it did allow me to do is determine where the issue is coming from as before it was too random to allow easy troubleshooting but now as it is more consistent it was quite quick to narrow it down.
I've cut this line (which is shielded with only one end of the shield grounded) and installed a connector. With it disconnected, the EM2 display is rock steady (up to a 10 minute ground run) but with no RPM or any fuel, power, or efficiency data. Connect the line and it immediately will scramble. I estimate that the frequency of the injector pulse on this line would only be at max about 100Hz at 6000 RPM. I've considered that a simple low pass RF filter to ground may work as the frequency that I'm trying to measure is well below what the filter would remove, but would it still have an effect on the pulse width? which would be undesirable as that would effect the signal driving the #1 primary injector.
I'm hoping that someone can suggest an easy fix so that I can implement it when I get back up to the airport this weekend, other wise if more data is needed to help find a solution I will take a scope up there and try to get some more detailed data.
Right now our days are getting pretty short up north here so it's dark by the time I get off work, so I'm restricted to weekends only. Thanks for any help that can be provided.

Todd Bartrim

RV9 13Bturbo


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yellowduckduo(at)gmail.co
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PostPosted: Tue Nov 05, 2019 6:18 am    Post subject: Engine monitor display scramble from EFI sense line EM2 fro Reply with quote

Rather than adding filtering that was previously not needed I'd start by
confirming ground integrity.  FIrst in external wiring and then for
circuit board solder joints. Then I test and usually replace any
electrolytic caps in the sensing circuit and power supply circuitry. 
Selectively warming (drying) or cooling (freeze spray) the circuit board
components is a quick test that can help narrow things down.  Eventually
I look at whether the input signal itself has changed but in my limited
experience that is more likely on ignition sensing than on an injector
sensing if the grounds are good.  I have not worked on any RWS systems. 
The good news is that now that you can immediately trigger the fault,
your chances of finding the problem are much improved.  With analog
inputs I also like to clean the board with alcohol when humidity is
suspected but I doubt that is a problem with your digital pulse sending.
Ken

On 05/11/2019 4:03 AM, Todd Bartrim wrote:
Quote:
I have an issue with my engine monitor display where the display will
scramble leaving me with a meaningless display as can be seen in the
attached picture
EM2 display_scrambled.jpg
The engine Monitor is from Real World Solutions and is the very early
first edition EM2 (serial #003). I also have an early edition EC2
(engine ignition and injection controller).
RWS was Tracy Crooks company before he retired, and he still provides
some support when he can, however he also is enjoying his
retirement offline so is often hard to get a hold of,
so I thought I would pose the question here while awaiting a response
so maybe I won't even have to bother him.

  So here are the details of the problem. The engine monitor has 36?
different parameters that it displays on 8 screens. There are 24
different sensors (pressure, temperature, level) with the remaining
being provided through a serial data link from the EC2 along with an
EFI sense which is connected to the #1 primary injector output from
the EC2. I've determined that it's this last wire that is causing my
grief.
This EFI sense is measured for it's pulse width in order to calculate
a surprisingly accurate fuel flow, RPM, HP, fuel remaining, MPG (for
efficiency). But the noise on this line seems to be the cause of the
data scrambling on the display. Simply pressing the cancel button
(there are 4 user buttons to control display) will rest and clear the
issue.
   But here's the weird part. It seems to be related to relative
humidity. During hot dry, summer weather this display will rarely
scramble, sometimes going up to an hour without an issue. But on
cooler humid days I would have to reset it every few minutes which
gets a little annoying. However right now as we are not enjoying the
cold November rains before winter will arrive with cold dry weather,
I'm finding that it is scrambling almost immediately after a reset.
This makes no sense to me, but I've observed this pattern enough to be
sort of certain that it is not a coincidence... but I could be wrong.
In any event, it matters not whether it is or isn't triggered more by
the humidity, but what it did allow me to do is determine where the
issue is coming from as before it was too random to allow easy
troubleshooting but now as it is more consistent it was quite quick to
narrow it down.
  I've cut this line (which is shielded with only one end of the
shield grounded) and installed a connector. With it disconnected, the
EM2 display is rock steady (up to a 10 minute ground run) but with no
RPM or any fuel, power, or efficiency data. Connect the line and it
immediately will scramble. I estimate that the frequency of the
injector pulse on this line would only be at max about 100Hz at 6000
RPM. I've considered that a simple low pass RF filter to ground may
work as the frequency that I'm trying to measure is well below what
the filter would remove, but would it still have an effect on the
pulse width? which would be undesirable as that would effect the
signal driving the #1 primary injector.
  I'm hoping that someone can suggest an easy fix so that I can
implement it when I get back up to the airport this weekend, other
wise if more data is needed to help find a solution I will take a
scope up there and try to get some more detailed data.
 Right now our days are getting pretty short up north here so it's
dark by the time I get off work, so I'm restricted to weekends only.
Thanks for any help that can be provided.

Todd Bartrim

RV9 13Bturbo


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johnbright



Joined: 14 Dec 2011
Posts: 165
Location: Newport News, VA

PostPosted: Tue Nov 05, 2019 6:46 am    Post subject: Re: Engine monitor display scramble from EFI sense line EM2 Reply with quote

[quote="kjashton(at)vnet.net"]Just watching a video the other day about old solder joints that break or crack due to hot/cold cycles or mechanical stress. They are difficult to detect with the eye but I think I would try to touch as many of your joints as possible with a small soldering iron.
-Kent

I had this happen on an automotive dashboard mounted environmental control that worked intermittently. The circuit board had a control side and a power side. Some of the power side solder joints looked like this photo. I had a theory it happened on the power side due to greater thermal excursions perhaps in combination with other factors. Remelting fixed it.


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PostPosted: Wed Nov 06, 2019 12:13 am    Post subject: Engine monitor display scramble from EFI sense line EM2 fro Reply with quote

I think I may have found the culprit in a bad solder joint on the DB37 connector that is used. It was not on the pin used for the injector pulse in question but on a nearby pin that is used for the crank angle sensor, which is known to be a noisy signal at the best of times so careful shielding and routing of the wires is called for. Unfortunately inside the crowded confines of a DB37 connector back-shell, this is a difficult task to isolate from the other wires sharing this connection. So a bad solder joint on an already known noisy wire packed tightly with my suspect wire, sounds like a plausible cause.   Quick and easy repair, but I'll have to wait until the weekend to go back up to the airport to test it.
Thanks for the comments

Todd Bartrim
On Tue, Nov 5, 2019 at 6:24 AM C&K <yellowduckduo(at)gmail.com (yellowduckduo(at)gmail.com)> wrote:

Quote:
--> AeroElectric-List message posted by: C&K <yellowduckduo(at)gmail.com (yellowduckduo(at)gmail.com)>

Rather than adding filtering that was previously not needed I'd start by
confirming ground integrity.  FIrst in external wiring and then for
circuit board solder joints. Then I test and usually replace any
electrolytic caps in the sensing circuit and power supply circuitry. 
Selectively warming (drying) or cooling (freeze spray) the circuit board
components is a quick test that can help narrow things down.  Eventually
I look at whether the input signal itself has changed but in my limited
experience that is more likely on ignition sensing than on an injector
sensing if the grounds are good.  I have not worked on any RWS systems. 
The good news is that now that you can immediately trigger the fault,
your chances of finding the problem are much improved.  With analog
inputs I also like to clean the board with alcohol when humidity is
suspected but I doubt that is a problem with your digital pulse sending.
Ken

On 05/11/2019 4:03 AM, Todd Bartrim wrote:
> I have an issue with my engine monitor display where the display will
> scramble leaving me with a meaningless display as can be seen in the
> attached picture
> EM2 display_scrambled.jpg
> The engine Monitor is from Real World Solutions and is the very early
> first edition EM2 (serial #003). I also have an early edition EC2
> (engine ignition and injection controller).
> RWS was Tracy Crooks company before he retired, and he still provides
> some support when he can, however he also is enjoying his
> retirement offline so is often hard to get a hold of,
> so I thought I would pose the question here while awaiting a response
> so maybe I won't even have to bother him.
>
>   So here are the details of the problem. The engine monitor has 36?
> different parameters that it displays on 8 screens. There are 24
> different sensors (pressure, temperature, level) with the remaining
> being provided through a serial data link from the EC2 along with an
> EFI sense which is connected to the #1 primary injector output from
> the EC2. I've determined that it's this last wire that is causing my
> grief.
> This EFI sense is measured for it's pulse width in order to calculate
> a surprisingly accurate fuel flow, RPM, HP, fuel remaining, MPG (for
> efficiency). But the noise on this line seems to be the cause of the
> data scrambling on the display. Simply pressing the cancel button
> (there are 4 user buttons to control display) will rest and clear the
> issue.
>    But here's the weird part. It seems to be related to relative
> humidity. During hot dry, summer weather this display will rarely
> scramble, sometimes going up to an hour without an issue. But on
> cooler humid days I would have to reset it every few minutes which
> gets a little annoying. However right now as we are not enjoying the
> cold November rains before winter will arrive with cold dry weather,
> I'm finding that it is scrambling almost immediately after a reset.
> This makes no sense to me, but I've observed this pattern enough to be
> sort of certain that it is not a coincidence... but I could be wrong.
> In any event, it matters not whether it is or isn't triggered more by
> the humidity, but what it did allow me to do is determine where the
> issue is coming from as before it was too random to allow easy
> troubleshooting but now as it is more consistent it was quite quick to
> narrow it down.
>   I've cut this line (which is shielded with only one end of the
> shield grounded) and installed a connector. With it disconnected, the
> EM2 display is rock steady (up to a 10 minute ground run) but with no
> RPM or any fuel, power, or efficiency data. Connect the line and it
> immediately will scramble. I estimate that the frequency of the
> injector pulse on this line would only be at max about 100Hz at 6000
> RPM. I've considered that a simple low pass RF filter to ground may
> work as the frequency that I'm trying to measure is well below what
> the filter would remove, but would it still have an effect on the
> pulse width? which would be undesirable as that would effect the
> signal driving the #1 primary injector.
>   I'm hoping that someone can suggest an easy fix so that I can
> implement it when I get back up to the airport this weekend, other
> wise if more data is needed to help find a solution I will take a
> scope up there and try to get some more detailed data.
>  Right now our days are getting pretty short up north here so it's
> dark by the time I get off work, so I'm restricted to weekends only.
> Thanks for any help that can be provided.
>
> Todd Bartrim
>
> RV9 13Bturbo

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