Today's Message Index:
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1. 12:13 AM - Re: Engine monitor display scramble from EFI sense line EM2 from RWS (Todd Bartrim)
2. 04:25 PM - =?utf-8?Q?Using_a_BNC_=9CT=9D? (Carlos Trigo)
3. 06:04 PM - =?UTF-8?B?UmU6IEFlcm9FbGVjdHJpYy1MaXN0OiBVc2luZyBhIEJOQyDigJxU4oCd? (Kelly McMullen)
4. 09:14 PM - =?utf-8?Q?Re:__Using_a_BNC_=9CT=9D? (Eric Page)
Message 1
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| Subject: | Re: Engine monitor display scramble from EFI sense |
line EM2 from RWS
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@gmail.com> wrote:
>
> 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
>
>
Message 2
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| Subject: | =?utf-8?Q?Using_a_BNC_=9CT=9D? |
=EF=BBGuys
I=99m sure this has been asked (and answered) before, but I am too old
for my memory to remember of it, and too lazy to look for it in the archive
s...
I have just installed a 2nd Comm antenna in my aircraft, a plain vanilla RAM
I AV-10, which is intended to be used either by a future Comm 2 radio or by a
hand-held radio which I will carry in my flight bag.
For that purpose I installed 2 antenna cables, one which goes from the anten
na to the place where I planned to put the future Comm 2 radio, and the othe
r cable goes from the antenna to somewhere near the pilot seat, where a loos
e end with a female BNC connector will be connected to the hand-held radio i
n case I need to use it.
So, the question is: is it ok to install a =9CT=9D like these
below the antenna, and connect to it the 2 cables mentioned above?
Thanks
Carlos
Enviado do meu iPhone
Message 3
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| Subject: | =?UTF-8?B?UmU6IEFlcm9FbGVjdHJpYy1MaXN0OiBVc2luZyBhIEJOQyDigJxU4oCd? |
What are you trying to do? Why would you want a Tee? If I understand
correctly you want to connect one antenna to panel mount radio, then
connect the second antenna to your handheld. You do NOT want to tie the
two antennas together.
On 11/6/2019 5:23 PM, Carlos Trigo wrote:
> Guys
>
> Im sure this has been asked (and answered) before, but I am too old for
> my memory to remember of it, and too lazy to look for it in the archives...
>
> I have just installed a 2nd Comm antenna in my aircraft, a plain vanilla
> RAMI AV-10, which is intended to be used either by a future Comm 2 radio
> or by a hand-held radio which I will carry in my flight bag.
> For that purpose I installed 2 antenna cables, one which goes from the
> antenna to the place where I planned to put the future Comm 2 radio, and
> the other cable goes from the antenna to somewhere near the pilot seat,
> where a loose end with a female BNC connector will be connected to the
> hand-held radio in case I need to use it.
>
> So, the question is: is it ok to install a T like these
>
>
> below the antenna, and connect to it the 2 cables mentioned above?
>
> Thanks
> Carlos
>
>
> Enviado do meu iPhone
Message 4
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| Subject: | Re:_AeroElectric-List:_Using_a_BNC_=9CT=9D? |
> On Nov 6, 2019, at 4:23 PM, Carlos Trigo <trigo@mail.telepac.pt> wrote:
>
> I have just installed a 2nd Comm antenna in my aircraft...
Carlos, the short answer is no. The extra length of open-ended coax will ru
in the impedance match between either radio and the antenna, and transmittin
g on one radio with the other connected through the tee might well result in
(expensive) tears.
This situation calls for either:
1) A coaxial switch that connects the antenna to only a single radio at a ti
me and disconnects the other; or,
2) Delete the tee and leave both lengths of coax in place. Connect the ante
nna to the coax feeding your handheld for now. When you later install the C
omm 2 radio, connect that coax at the antenna and remove or abandon the one t
o the handheld.
Eric
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