SNIP
> Mark,
>
> The shielding on millivolt and milliamp wiring is either
terminated at
> the device end or the "control" end (reading end) of the circuit but
> not both OR neither, and it should be connected to the ground bus or
> terminal(s). The shielding should be "continuous" from probe to your
> reading device/control device. There is a quick treatise on:
>
>
http://www.omega.com/prodinfo/Thermocouples.html
>
> What size was the hole you drilled (diameter) for the
thermocouple you
> inserted? I think that's pretty cool that you made your own by
welding
> the bi-metal wiring together. Never heard of anyone doing that.
>
> Allen
> Allen,
> There is a metal tip that fits into the exhaust header that the
> shield is attached. I never really thought much about it, but I
> imagine that provides the ground for the shield (from the exhaust
> system to the engine block and then to ground).
>
> As for welding the ends of the TC wire for the CHT probes, I believe
> I got that idea from Tracy Crook. I'm not sure he suggested using a
> TIG welder, but the idea was the same. Worked great (price was
> right too). So, should the tc leads be shielded?
--------------------------------------------------------------
We used to make Thermocouples using a 'Variac", and a pool of
mercury under oil. Insert a lead from the Variac into the mercury,
connect the other lead to the twisted together TC wire, and dip it
through the oil into the mercury. It will arc weld the TC tip, and
the oil keeps the mercury vapor down. OHSA probably would object now.
Bill Schertz
Bill,
That's very interesting. I'm used to specifying and buying
thermocouples from instrument vendors. That includes the thermowell.
That's why I was curious as to the size/diameter of the hole that Mark
drilled in his block. I was going to see if I could find something that
would work that was "off the shelf". That would include a thermowell,
thermocouple and whatever else was needed to install it. I'm not sure
that the bimetal wiring stuck in the hole would continue to give
adequate information.
Allen
Houston
Allen, Do you know about omega.com. They have tons of thermal couples.
http://www.omega.com/toc_asp/sectionSC.asp?section=A&book=temperature
Wire down to .005 inches in diameter.
Paul Lamar ...No rotor no motor.
Paul,
Yes, I do and that's why I thought that Mark could get a more
"industrial" installation if he had a thermowell to fit the hole he
drilled. Typically in industrial applications, thermowells are
installed in the hole where temps are to be measured and then a
thermocouple is threaded/screwed into the thermowell. (I hope I'm not
insulting anyone with this instruction). If Mark could cut some
threads in the top of his drilling there might be a "thermocouple" that
could be purchased that could be threaded into his hole without a
thermowell. The thermocouple of course would need to bottom out or
touch the bottom of the hole to achieve the best measured results.
Typically, thermocouples are 316 SS but have a welded tip where the
bimetal wires are fused together inside of it. One could be made
"special" to fit probably for about $150- I'm guessing. Type J sounds
like the right range for his block thermal measurements. There are
other temperature vendors out there that I work with, so I thought I'd
just check around for him. All I need is hole diameter, depth, temp
range. The millivolt output of course will vary with the temp range and
I don't know what device he is using to read/monitor/log this info.
Allen
Houston
You want to minimize the size of the hole here as this is a high
stress area of the rotor housing. What is the smallest size
Thermowell you can get?
We are going to use something from Omega called Omegabus D5321
Each device records four thermocouples values directly on
the hard disk. Search Google for Omegabus D5321. These are
K thermocouples -150 to 1250C. We also have one J Unit
Model D1311
http://www.omega.com/
The CHT runs from 200 to 600 F
Paul Lamar ...No rotor no motor.
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