Got a new pyrometer but...

[Diesel JD]

It still doesn't read right, so I must have something going on with my thermocouple or leads. This thermocouple is new as of last August, type K from Omega Engineering and did work. I think my problem is in the leads, way too cut and spliced I guess. Do I need a factory designed thermocouple lead, or can I make an acceptable one with some Omega thermocouple wire I have here? If so, what kind of terminals do I need? Thanks a lot guys.

 

[Diesel JD]

Bump> no info on this here?

 

[suv7734]

What do you mean when you say it doesn't read correctly? Do you have the correct leads to work with the type K? If there are connections made in the leads they need to be done with proper physical crimps and no solder. Solder will introduce another metal into the mix and possibly create false voltages.
Just a few things to consider...

 

[RLDSL]

If the lead wire has been cobbled , that sounds like the problem. Most pyrometer lead wires can't be shortened/lengthened by cut and splice , you have to buy complete sections that are matched to the gauge.

 

[Agnem]

While a pyrometer is a basic device that it would seem easy to cobble together, I find the pyrometer probe/connection lead kits that are sold (like the ones from ISSPro) to be the best source for dependable readings. You're right that a type K is a type K, but the way the probe kits are sold - with ring terminals that you use little bolts to hold together, and insulating sleeve tubing that you slide over them.. makes me think that all these additive resistances are very carefully calculated. It's also by no coincidence I'm sure that the total lenght of a probe wire connection kit is just enough to go from the A pillar to the right exahust manifold, sometimes by the shortest possible route. I had a pyro go bad on my once (or so I thought), and it turned out to be a problem with the wiring that I could never figure out. Just replaced it with another probe connection kit, and it was right as rain.

 

[Dirtleg]

Here is my experience.

I have installed many a thermocouple in different types of process equipment. If it is a type K then you can replace it with a type K. The wire will also have to be type K and the polarity of the wires must be run in the proper direction. Yellow is + red is -. It is possible to have junctions in the line but as SUV7734 mentioned the quality and type of connection will determine the accuracy of the reading through it. I have had good success running 100+ ft of thermocouple wire through 3-4 junctions before they reached the point where they were read from.

I have also taken a thermocouple and split the wiring at a connection to read at 2 different locations through 2 different gauges and not had any problems with that either.

Now if the gauge itself is calibrated for a certain amount of resistance then you should be O.K. if you use the same length and size wire as what would come with the gauge. Use butt-crimp connectors and heat shrink them once finished.

 

[Diesel JD]

Well you guys just educated me about the eistence of different types of thermocouple wiring. The wire I have uses a red wire and a blue wire, doesn't say what the polarity is. I assumed red was negative blue positive. I used a redneck type splice right before the gauge and tiny wire nuts on the probe lead wire. I suppose its back to the old drawing board eh? Thanks,
JD

 

[reklund]

You should start with a thermocouple that matches your gauge, to be sure. Also wire nuts should NEVER be used in an automotive application...they're intended for use in a stationary gang box in a house that doesn't see the elements or vibration that a vehicle sees. A proper crimp connector with insulation and/or heat shrink is the prefferred method.

As Mel (Agnem) said, the thermocouples that use the little ring termnials and bolts are designed specifically for the included resistance in the wire, terminals, and gauge and as such should be used as a "matched" set for the most accurate readings.

Ryan

 

[sle2115]

I have a dual sweep Westach, so my information may not apply. In an email, I was told that as long as I didn't change the length of the lead on the thermocouple, I could use wire in between the gauge ends and the guage, up to 20 feet and it had to be a certain gauge (22 IIRC). At any rate, I used about 4 feet and they seem to work fine.

Can you elaborate on why you think it is not reading correctly?

Oh, and about the best laymans wire connector can be had from 3m and Wally World used to carry them, assume they still do. They are crimp and shrink wrap all together. You crimp them on, then heat them and they have a sealant in them that glues and seals everything once heat is applied. They are like $6 for 10 or so, but it is money well spent.

 

[suv7734]

Well you guys just educated me about the eistence of different types of thermocouple wiring. The wire I have uses a red wire and a blue wire, doesn't say what the polarity is. I assumed red was negative blue positive. I used a redneck type splice right before the gauge and tiny wire nuts on the probe lead wire. I suppose its back to the old drawing board eh? Thanks,
JD

JD,

What color are the leads off the thermocouple? If it is a type K they should be red (-) and yellow (+). The extension wire that runs from the thermocouple to the gauge should also be red/yellow leads with a yellow casing (for type K). If you have thermocouple extension wire that is red/blue leads with a blue casing that is meant for a type T thermocouple. What brand of gauge are you working with? Just an FYI, Isspro has extension wires available in lengths up to 14' and special order up to 75'.

 

[Diesel JD]

Well it looks like the problem is that I'm using thermocouple wire intended for a Type T which is not what I have. The thermocouple has red and yellow leads which match red-, y+ polarity. So I guess I need to either buy some proper thermocouple wire or buy a type K lead, and then figure out the best crimps(the 3M ones sound good, I'll use that or similar) and FYI the gauge is actually intended for a big truck, but it uses the Type K thermocouple we use and reads 0-1800*F so its useful for this application I would imagine. It is a Stewart-Warner brand with 180* Sweep. The seller said that NAPA carries/can get Stewart Warner gauge stuff including pyrometer leads, so perhaps I'll need to call them or an ISSPRO dealer and see who has the best stuff, or I'll just buy some of the right kind of Type K wire from Omega. I figured it might be something like this. Thanks guys.