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1951 Pontiac Chieftain


PhilA

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Took some measurements of the TU-4 sensor.

 

100F is 280 ohms

180F is 100 ohms

230F is 50 ohms

 

Gonna tweak the coils to match now. Rewound to standard to make sure it was actually working (it is). Gonna pull some turns off the left coil to boost how powerful it is.

 

Phil

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Somewhere in the approximate ball park.

 

post-5454-0-88589000-1544665615_thumb.jpg

 

Further refinement required, I am going to put the sensor in water to hold the temperature longer, and that I can put a thermometer in easily. My infrared thermometer has issues with the shiny brass (I put some matte black paint on it earlier which was kinda ok).

 

 

Phil

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I had a bit of a poke about, I'm currently plotting temperature versus resistance of the sender.

 

post-5454-0-58088500-1544901816_thumb.jpg

 

Trying to get the balance of the two coils right- because it's a voltage divider in two coils at right angles, the mathematics has broken my brain so I'm just experimenting right now.

 

Phil

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Thinking on this, to increase the magnetic flux, I must increase the current flowing through the coil.

 

I can do that by reducing the length of the wire, and thus the resistance; however in so doing the number of turns around the bobbin reduce, so in practice net result is more heat produced for very similar magnetic flux.

 

So, the same length of wire is required but more current must pass through it to create a greater flux. Increase the gauge of the wire and more current will flow.

 

I don't have a bigger gauge wire right now so what I can do is wind two lengths of wire on in parallel. I'm going to try see if I can do that tomorrow, if time allows.

 

If my theory is sound then I'll order some larger gauge wire and go from there.

 

Phil

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And, I suppose I rather am due providing a bit of an explanation.

 

I think really the simplest way to describe the gauge setup is to use a tug-of-war analogy.

 

Each coil is a team in either end of the rope. The needle position is how far the flag in the center is away from the middle.

 

You bias one team with a few less people, so with no instruction one team is always pulling the other to the end of their run. The needle reads cold.

 

The temperature sender is the equivalent of telling the team with more people to pull less. Eventually they are overcome by the strength of the other team (who are always pulling as hard as they can) and the flag begins to move in their favor.

 

The less you tell the bigger team to pull, the more they are overcome and eventually the smaller team will pull them across (needle reads hot).

 

So, my problem is the bigger team needs to pull with less strength per instruction to pull less.

 

The other team always pull as hard as they can. With the old sensor they'd have to pull 30 pounds less to start to move the flag; now they should only have to pull 10 pounds less to begin to move it.

 

Now work that out where the amount of pull one team makes isn't actually always the same and they're actually pulling at right angles with a flag that changes weight as they pull it...

 

 

Phil

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