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- For a PC case I am building I decided I wanted to get all official and be able to measure the temperatures accurately. I had a simple voltmeter, but decided to buy another one that could measure temperatures–and I also had wanted a DMM that had a freq counter as well. I found a suitable DMM at an online retailer, and the price of it 9$60) was under their minimum order limit ($75)–so I also bought a temperature adaptor ($30) that fits into the jacks of a regular DMM and provides a mV output equal to the temperature (it has a switch for F or C, and the new DMM measures with the K-type probe plugged into it directly).
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- First of all after unpacking them and plugging them in, I was rather miffed that both did not read the exact same room temperature. For what it’s worth, the $30 temperature convertor reads in one-tenth of a degree where the auto-ranging DMM only reads in whole degrees. It’s much easier to see that the convertor-temperature reading has settled than it is with the DMM, and the convertor settles down quicker too. After a couple minutes, both read within one degree of each other. Neither of these are calibrated units.
- Both temperature-probe jacks are K-type thermocouples, and both came with a bead probe. Are the leads of this probe made of regular wire, or are they capilaries that contain mercury? The metal is silver and is very stiff, it appears to be steel–not any thing soft like copper. It might have to do with them being rated for the temperatures they are (one probe says 398F and the other says 600F). Do these things withstand a lot of bending? I know they don’t cost a lot to replace (~$12), but I don’t know if there’s anywhere locally that keeps them on hand.
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There are no capillaries filled with mercury. There are just two types of disimilar metal welded together. This junction, when heated or cooled, produces a voltage which is interpreted as a temperature. The connecting wires are not something that you can get off the shelf as they are matched resistively so the changes in temperature have the same effect on both. Of course, you can use anything you have laying around, but this will affect the accuracy of the device.
The wires are made of the same materials as the junction. For K type, one is a nickel-chromium alloy and the other is a nickel-aluminum alloy. They are plain wires, but in my experience they seem more brittle than copper wire.
Do you mean they aren’t standard copper wires, or do you mean they need to be matched to individual thermocouples? I’ve bought thermocouple wire off the shelf and didn’t have any problems as long as I got the correct type (i.e. specify K-type for K-type thermocouple).
For two separate thermocouples in air? Heck, that’s not bad at all. I’m not sure if you’re aware or not, but thermocouples are not very accurate. A one degree difference is considered pretty good.
As others have said, neither. It’s simply two wires of different composition connected together.
That’s the insulation rating. The metal wires themselves are rated much higher.
Depends on the gage, and whether each conductor is made from stranded or solid wire. At any rate, I wouldn’t bend them any more than necessary.
We have thermocouple wire coming out the ying-yang where I work. If you need some wire, just visit the engineering department of a local university and ask for a few feet of type K wire. You’ll have to make a junction, but that’s easy. While a weld is the ideal junction, just about anything will work for what you want to do (solder, twisting, etc.)
I just meant you’re not going to find it at home depot, radio shack, or best buy. You can find anything if you’re resourceful enough. Being here is a good, first step. 