Today's Message Index:
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1. 12:36 AM - Re: turn coordinator causing noise in headset (D L Josephson)
2. 06:10 AM - Re: Re: turn coordinator causing noise in headset (Robert L. Nuckolls, III)
3. 07:08 AM - Re: turn coordinator causing noice in headset (jerrytex)
4. 03:08 PM - thermocouple calibration (rayj)
5. 04:17 PM - Re: thermocouple calibration P.S. (rayj)
6. 05:01 PM - Re: thermocouple calibration P.S. (rayj)
7. 06:32 PM - Re: Compatable Shunt (fedico94@mchsi.com)
Message 1
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Subject: | Re: turn coordinator causing noise in headset |
> From: "jerrytex"<jery230@tconline.net>
>
>
> The noise is there always, regardless of transmitting or receiving. I can put
my
> headset on, turn on the master, listen to the gyro spin up in the headset, then
> turn on the landing the light, and the noise goes away. Or I can disconnect
> the antenna, and the noise goes away. I read on a yahoo group in which someone
Unless the noise is actually breaking squelch in the radio I'm going to
bet on common impedance coupling aka a ground loop, and that your rubber
duck antenna cable is still making a connection to the airframe
somewhere. Is the headset connected directly to the radio, or to an
intercom? Anyway, try the capacitor and then a better filter. Keep the
leads (of either) very short, connect right at the connector of the t/c.
Message 2
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Subject: | Re: turn coordinator causing noise in headset |
Unless the noise is actually breaking squelch in the radio I'm going
to bet on common impedance coupling aka a ground loop, and that your
rubber duck antenna cable is still making a connection to the
airframe somewhere.
Is the headset connected directly to the radio, or to an intercom?
Anyway, try the capacitor and then a better filter. Keep the leads
(of either) very short, connect right at the connector of the t/c.
Waaayyyy back when, there was a t/c noise incident that
proved to be MAGNETIC radiation directly from the innards
of the instrument. I don't recall now what brand. THAT
fix called for wrapping the plastic instrument case with
ferrous sheet metal. I think he cut it from a gallon can
and put two or three layers around it secured with tie
wraps.
Never had these problems when suck-n-blow systems were
king . . .
Bob . . .
Message 3
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Subject: | Re: turn coordinator causing noice in headset |
I tried the capacitor and it didn't make any difference. I went ahead and filled
out the order for the filter and I'll give that a try.
In response to the question about the intercom....the headset is hooked up to an
intercom. I have isolated the headset jacks with plastic washers. The noise
only can be heard when the radio is on. With just the intercom on, there is no
noise.
Thanks again for the responses.
Jerry
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=385918#385918
Message 4
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Subject: | thermocouple calibration |
Greetings,
I calibrated the 3 TM-902C hand held instruments. I was able to adjust
them to read the same at both 0 and 100 deg C. It seemed to take 2-3
cycles from cold to hot and back to get them to settle down, but once
they did they all were very consistent at both ends of the range tested.
As I reviewed Bob's posting I noticed that the boards in mine are a
different layout than the one pictured. I'll include a picture of mine
if I can get to upload.
On mine one adjustment point is to the left of the yellow connector
(6:30 position) near the edge of the board. The second is located at
the 3:00 position.
The 6:30 position adjusts the readout at 0 deg C. The 3:00 position
adjusts the readout at 100 deg C. As I mentioned earlier it seemed to
take 2-3 cycles before it becomes stable.
On both adjustments turning clockwise lowered the value displayed. CCW
raised it.
thermo2
--
Raymond Julian
Kettle River, MN.
"And you know that I could have me a million more friends,
and all I'd have to lose is my point of view." - John Prine
Message 5
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Subject: | Re: thermocouple calibration P.S. |
Message 6
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Subject: | Re: thermocouple calibration P.S. |
2nd try!
P. S. to the post below.
The procedure I used was to immerse the probe in ice water and adjust
the display to 0 deg C. Next was to immerse the probe in boiling water
and adjust the display to 100 deg C. Repeat until no further adjustment
is needed.
Raymond Julian
Kettle River, MN.
"And you know that I could have me a million more friends,
and all I'd have to lose is my point of view." - John Prine
On 10/24/2012 05:07 PM, rayj wrote:
> Greetings,
>
> I calibrated the 3 TM-902C hand held instruments. I was able to
> adjust them to read the same at both 0 and 100 deg C. It seemed to
> take 2-3 cycles from cold to hot and back to get them to settle down,
> but once they did they all were very consistent at both ends of the
> range tested.
>
> As I reviewed Bob's posting I noticed that the boards in mine are a
> different layout than the one pictured. I'll include a picture of
> mine if I can get to upload.
>
> On mine one adjustment point is to the left of the yellow connector
> (6:30 position) near the edge of the board. The second is located at
> the 3:00 position.
>
> The 6:30 position adjusts the readout at 0 deg C. The 3:00 position
> adjusts the readout at 100 deg C. As I mentioned earlier it seemed to
> take 2-3 cycles before it becomes stable.
>
> On both adjustments turning clockwise lowered the value displayed.
> CCW raised it.
> --
> Raymond Julian
> Kettle River, MN.
>
> "And you know that I could have me a million more friends,
> and all I'd have to lose is my point of view." - John Prine
Message 7
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Subject: | Re: Compatable Shunt |
The 60 amp alternator reads now on the G3X system. I do not have a reading on
the Auxillary alternator even though I have installed another 50 mv/100 amp shunt.
When I get the cowling off then I will switch the wires. The auxillary
alt ammeter still has a red "x" through it. How did things work out with the
folks at Garmin ? Any new insights ?
----- Original Message -----
From: Robert L. Nuckolls, III <nuckolls.bob@aeroelectric.com>
Sent: Mon, 1 Oct 2012 08:55:49 -0500 (CDT)
Subject: Re: AeroElectric-List: Compatable Shunt
> The shunt sent to me by the Avionics shop for use with the Garmin
> is 100 amp/50mv and the one B & C supplied and installed in the
> plane is 60 amp at 50mv. My confusion and question concerns the
> schematic from Garmin that says the shunt is rated at 0.0005
> Ohm. The B & C supplied system with its shunt is 50mv/60 amp gives
> me 0.00083 Ohm.
>
>First are my calculations correct and second does this have any
>bearing on the inability to display the ammeter reading ? If the
>above is not contributing to the problem should I look elsewhere in
>the system for the problem ? (Prior to turning on the field of the
>60 amp alternator I get the main volts waring light flashing and
>goes off after the field is activated. Remainder of G3X works fine)
The size of the shunt is relative only to calibration
of the display. If you have no display, then the problem
is not with the shunt. If the display is present but
inaccurate, THEN you probably have a shunt problem.
A shut is just a high power resistor . . . abeit a special
resistor manufactured from amazium alloy with a near
zero temperature coefficient of resistance. The material
is actually Manganin.
http://tinyurl.com/3f79fgy
When your current display is a LOADMETER calibrated
in 0-100%, then the shunt is sized to what ever that
100% value is . . . in case of the 60A alternator,
you would use a 60A shunt. If it were a 100A alternator,
then a 100A shunt. Interestingly enough, using a 100A
shunt in ALL installations converts the 0-100% display
to a 0-100A display.
I suspect that the 100A shunt recommended by the
avionics shop is based on some knowledge that the
EFIS calls 50mv drop 100Amps and that size shunt
will read ANY practical current up to 100A accurately.
Substitution of a 60A shunt would simply mean that
your 100A display was really a 100% display.
Looking past calibration issues, if your display is
non-reading, the difficulty lies elsewhere.
Bob . . .
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