Today's Message Index:
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1. 06:13 AM - Re: Re: Extending thermocouple leads (Robert L. Nuckolls, III)
2. 01:28 PM - Starter contactor leaking voltage (Mickey Coggins)
3. 07:25 PM - Re: Extending thermocouple leads (Radioflyer)
Message 1
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| Subject: | Re: Extending thermocouple leads |
At 01:51 PM 8/3/2012, you wrote:
>
>Bob, thanks for your reply. You asked what the spade terminals were
>attached to. They are crimped on to the J wires of the thermocouple
>sensor. The wires are red and white and one of them was magnetic.
Do the terminals terminate to a 'sensor' under
the cowl or to an instrument behind the panel?
>You are right that a few degrees of error would not much matter for
>CHT readings. I don't have a sense for how much error my
>"J-spade-J-spade-instrument" setup would introduce, but if within
>say ten degrees then it would be ok. I just want to be sure I can
>reliably tell that my cylinders are not exceeding max allowable temperature.
Sure. One way to check your instrument's
calibration with as-installed thermocouples is
to get one of those in-the-cup immersion heaters
for travel-coffee/tea and use it to raise a cup
of distilled or R/O water to boiling. You can
do this right next to the engine where you've removed
a cht sensor bulb and immerse it in the water.
Wait several minutes while the reading stabilizes.
Compare with boiling point of water at your
present atmospheric pressure conditions:
http://tinyurl.com/bmptwag
and you can see just how close the instrument
is to reading true at about 200F.
Bob . . .
Message 2
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| Subject: | Starter contactor leaking voltage |
Thanks Bob, Gents, for the feedback on this. I have done it the way the
plans show, and you suggested, and put the starter contactor on the FW.
New question (yes, I'm building very slowly) - I have the Van's starter
contactor (Part Number = ES 24021) and when I apply 12v to the battery
connection, I get about 0.4v on the starter connection. This is before it
is energized. When I apply the 12v to the 'S' terminal, I get the full 12v
on the starter terminal.
Is it normal for some voltage to "leak" even when the device is "idle"? My
battery contactors don't do this, and I don't have another starter
contactor to test with.
Thanks,
Mickey
Message 3
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| Subject: | Re: Extending thermocouple leads |
The extension (thermocouple) wire pair would eventually connect to an instrument
on the panel in the cabin. So, Engine side: thermocouple--spades--J wire pair
extension--thru firewall. Then Cabin side: extension cont'd--spades--copper--instrument
on panel. The extension is 12 feet long because this is in a pusher
aircraft. Spades to copper to instrument because I can't connect the J type
thermocouples wires directly to the DB15 on the instrument.
What I'm thinking is that the parasitic couple between spades and thermocouple
wire pair in the hot engine side, and the other parasitic couple of thermocouple
wire pair and spades in the cooler cabin will not much affect the absolute
temp readings.
--Jose
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http://forums.matronics.com/viewtopic.php?p=380062#380062
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