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dean.psiropoulos(at)veriz
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 Posted: Sun Jul 29, 2007 9:53 pm Post subject: Thermocouple wire connections |
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I've finally installed all my VM-1000 engine monitor harness and have only
to connect the it from the CPU to the pigtails on the EGT/CHT thermocouple
probes. Vision supplied the probes with about 2 feet of wire and faston
connections terminating them. I have to install fastons on the CPU harness
that connects to the probes and was going to use the fastons that Vision
supplied but they do not have the second crimp sleeve that provides
insulation strain relief. I have a bunch of the strain relief type fastons
but not sure if I should use them because it may mess up the readings due to
possible metallic connection mismatches between the thermocouple wire.
The fastons Vision supplied look to be coated with solder but I don't really
know if the underlying material is copper or something else (scratching the
surface doesn't yield a copper color underneath). The letters "T&B" are
stamped on these terminals. From looking at Bob's book it doesn't appear
that this is the way that these thermocouple wires should be spliced but I
assume that most Vision Micro buyers use what Vision supplies to assemble
their systems. I don't have a problem with this method but would prefer the
strain relief terminals if they will work. Otherwise I'll go ahead and
splice them with the supplied terminals.
Anyone else with VM-1000 have any thoughts? Can I use the strain relief
terminals or do I need to use the Vision terminals? The strain relief
terminals were purchased at a boat supply store so I suspect they are solder
coated copper, may not work for this application (the letters "I2" and "MX"
are stamped on these terminals). Also, the Vision fastons on the probe
pigtails are not encased in plastic but are installed with some heat shrink
around the crimp end. Can't tell if they are soldered but the install
manual doesn't say anything about soldering at the harness ends, just
crimping the terminals. Would I have to solder these for any reason? Any
words of wisdom Bob? Have you returned from OSH yet? Thanks.
Dean Psiropoulos
RV-6A N197DM
Will it ever end?
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bob(at)bob-white.com
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| Posted: Mon Jul 30, 2007 9:26 am Post subject: Thermocouple wire connections |
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On Mon, 30 Jul 2007 01:51:06 -0400
"DEAN PSIROPOULOS" <dean.psiropoulos(at)verizon.net> wrote:
| Quote: |
I've finally installed all my VM-1000 engine monitor harness and have only
to connect the it from the CPU to the pigtails on the EGT/CHT thermocouple
probes. Vision supplied the probes with about 2 feet of wire and faston
connections terminating them. I have to install fastons on the CPU harness
that connects to the probes and was going to use the fastons that Vision
supplied but they do not have the second crimp sleeve that provides
insulation strain relief. I have a bunch of the strain relief type fastons
but not sure if I should use them because it may mess up the readings due to
possible metallic connection mismatches between the thermocouple wire.
The fastons Vision supplied look to be coated with solder but I don't really
know if the underlying material is copper or something else (scratching the
surface doesn't yield a copper color underneath). The letters "T&B" are
stamped on these terminals. From looking at Bob's book it doesn't appear
that this is the way that these thermocouple wires should be spliced but I
assume that most Vision Micro buyers use what Vision supplies to assemble
their systems. I don't have a problem with this method but would prefer the
strain relief terminals if they will work. Otherwise I'll go ahead and
splice them with the supplied terminals.
Anyone else with VM-1000 have any thoughts? Can I use the strain relief
terminals or do I need to use the Vision terminals? The strain relief
terminals were purchased at a boat supply store so I suspect they are solder
coated copper, may not work for this application (the letters "I2" and "MX"
are stamped on these terminals). Also, the Vision fastons on the probe
pigtails are not encased in plastic but are installed with some heat shrink
around the crimp end. Can't tell if they are soldered but the install
manual doesn't say anything about soldering at the harness ends, just
crimping the terminals. Would I have to solder these for any reason? Any
words of wisdom Bob? Have you returned from OSH yet? Thanks.
Dean Psiropoulos
RV-6A N197DM
Will it ever end?
Hi Dean,
|
I don't have the VM-1000, but I do make quite a few TC extensions.
There are specialized connectors for connecting TC wires together.
They are large, expensive, and not necessary for the type measurements
made by an EGT probe. Soldering EGT wires is a tricky business. You
will need a very aggressive flux if you can do it at all. Crimp
connections are preferred and are just fine. I would use the PIDG
connectors from AMP because I know the quality.
I have used the shrouded connectors which don't have a metal ring to
support the wire. I used them because the particular EGT probe had them
installed. I used shrink tubing to build up the OD of the insulation
for a snug fit in the back of the connector and another shrink tubing
over the outside of the connector and the shrink tubing on the wire.
To minimize errors caused by the dissimilar materials, keep the
connectors on both wires at the same moderate temperature.
Bob W.
PS: I have a Tru Trak ADI for sale on ebay. Item 160142910426 for
anyone who might be interested.
--
N93BD - Rotary Powered BD-4 - http://www.bob-white.com
3.8 Hours Total Time and holding
Cables for your rotary installation - http://www.roblinphoto.com/shop/
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nuckollsr(at)cox.net
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| Posted: Mon Jul 30, 2007 9:45 am Post subject: Thermocouple wire connections |
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| Quote: | Can't tell if they are soldered but the install
manual doesn't say anything about soldering at the harness ends, just
crimping the terminals. Would I have to solder these for any reason? Any
words of wisdom Bob? Have you returned from OSH yet? Thanks.
Dean Psiropoulos
RV-6A N197DM
Will it ever end?
|
One is seldom wrong for following the manufacturer's instructions.
They've been building and selling these products for a very
long time. Be wary of dire predictions and helpful suggestions
to the contrary unless supported by more than reverence for
someone's traditions. At the end of the day, repeatable
experiments supported by simple-ideas rule the day.
If you were interested in harnessing the thermocouple leads
and assuming 20AWG wire or smaller, you could consider making
the engine to instrument harness transition in a D-sub connector
with machined pins. This too is a repeatable experiment.
Bob . . .
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nuckollsr(at)cox.net
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| Posted: Mon Jul 30, 2007 1:17 pm Post subject: Thermocouple wire connections |
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At 12:43 PM 7/30/2007 -0600, you wrote:
<nuckollsr(at)cox.net>
Can't tell if they are soldered but the install
manual doesn't say anything about soldering at the harness ends, just
crimping the terminals. Would I have to solder these for any reason? Any
words of wisdom Bob? Have you returned from OSH yet? Thanks.
Dean Psiropoulos
RV-6A N197DM
Will it ever end?
One is seldom wrong for following the manufacturer's instructions.
They've been building and selling these products for a very
long time. Be wary of dire predictions and helpful suggestions
to the contrary unless supported by more than reverence for
someone's traditions. At the end of the day, repeatable
experiments supported by simple-ideas rule the day.
Oh yeah, I forgot to add that just about anything you do that
contributes to measurement errors will be canceled out
as long as you do exactly the same thing to the other side
assuming that both "contamination" exist at the same
temperature. Sticking a splice in one lead has the potential
for creating one or more new thermocouples but equally
contaminating couples in opposing polarities will tend to
cancel each other.
If you were interested in harnessing the thermocouple leads
and assuming 20AWG wire or smaller, you could consider making
the engine to instrument harness transition in a D-sub connector
with machined pins. This too is a repeatable experiment.
Bob . . .
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captbly
Joined: 03 Aug 2007
Posts: 1
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| Posted: Fri Aug 03, 2007 9:57 pm Post subject: Re: Thermocouple wire connections |
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Dean,
The material of the connectors do not really matter as long as its the same material on both sides. Since there is no temperature difference on either side (as long as you dont have one connector laying against the engine), any effect is canceled out.
Now if you were making a connection at the firewall you would have a temperature difference on one side of the connector that would enduce a little bit of an error, all though this too probably isnt much.
The bigger issue is the mating of the two connectors. I would go with the Vision connectors (Thomas & Betts) first, when these fastons mate together they are very difficult to pull apart (a good thing) With the thermocouple wire the insulation crimp is negligible.
The probe end is just a crimp connection, it is not soldered.
best regards
dave
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deene(at)austin.rr.com
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| Posted: Sun Aug 05, 2007 7:36 pm Post subject: Thermocouple wire connections |
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Easy solution is to connect hat switch common to +14v and each other hat contact to each of the three relay board coil + connections respectively. Then use the three way switch to select the desired relay common coil ground connection to ground.
Deene Ogden
EAA Tech Counselor/Flight Advisor
[quote][b]
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