I have had this thermometer for probably a decade. About three years ago, I accidentally put the K type probe into something too hot and ruined it. Now it's time to get another probe, but I'm not sure which one. I lost the info on the thermometer, but here is an image:
Suggestions for both a manual and replacement probe would be welcome. Thanks in advance.
ars
hich
Please note that I know it needs a new K type probe, but I don't want to
end up overspending on a high temperature one if the meter won't range that high, but I can't find the meter specs online since I lost the manual.
All thermo coupler probes of the same leter are the same. There are several different letters used.
Just find any K type that the plug matches the instrument you are using. The plug should be made out of the same material as the t/c.
The most common plugs are usually the K and J type. They will not interchange and give the correct temperature.
You must have really stuck it into something hot. The K type is good for around 2000 deg F. You could have melted the probe if it was some sort of plastic, but the T/C should still be good unless it was over about 2000 deg F.
A thermocouple probe will range for whatever the letter of the probe is.
That is any K probe will work with any K meter. It does not matter what the display part of the meter is rated for. A TC probe is made of two types of metal and that only depends on what letter the meter part is made for.
You may pay more for the probe depending on the insulating material of the wires.
That seems to be an inexpensive meter and you can probably buy a new one similar to it off ebay for what the probe will cost you. There seems to be many like it with a few extra buttons.
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** Did you do any Googling at all?K type probes and wire tipped versions are all compatible with the same meters.
I like the tipped ones cos thermal inertia is so much smaller - means I can measure power semiconductor case temps in a few seconds.
..... Phil
Thanks. Yes, I did Google it but the uncertainty was the range of my meter and whether or not it made any difference. Doesn't appear to, so I will be ordering a replacement probe shortly.
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** Now, you need tell us that in your first post. ** What did you actually Google for?Cos I found this in about 30 seconds:
Most stand alone meters, like yours, cover the full range of a K-type thermocouple.
But probes and wire tipped jobs have upper temp limits due to the insulation used in making them.
If we don't know what you are doing - how can we possibly help you ?
.... Phil
About half of my various digital multimeters can be used as a thermometer using a Type-K thermocouple probe. Perhaps it's time to junk your 10 year old meter and just use a multimeter? Or, perhaps add some additional functionality, such as a data logger?
I can't deduce what style of Type-K probe you managed to destroy. So, pick a photo that looks familiar as any Type-K probe will work.
I prefer the bare thermocouple end with the common yellow flat blade type connector. For use on some instruments, I have an adapter to banana plugs. The wire is usually fiberglass wrapped to handle the heat. If I need a tip for better heat conduction or mechanical attachment, I stuff the tip into a copper or brass tube, and fill with whatever is handy. If I want accuracy, corrosion resistance, or high temp, I use a commercial probe. For example, for a >1000C kiln: Or, use tape or glue:
Hint: Perform a rough ice bath and boiling water sanity check on any probe you buy. I've seen a few surprises and built a few defective probes.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I just started using this glue for attaching thermocouples: About $8 for 4 oz. I can position the sensor, slop on some glue, hit it with some UV light, and I'm done in a few seconds. Of course, the bond is essentially permanent, so you have to do it right the first time.
Also, you can make your own thermocouples with a specialized welder: with a 12v car battery and a hammer: with almost any common heat welding method (oxy-acetylene, HHO hydrogen torch, Brown gas, etc): or if you have some environmentally incorrect mercury available:
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
A few things: K is a common thermocouple let's say if you wanted room temp or cryogenics then use T Type
Wire is made with limits of error. It's not great for knowing the traceable temperature. +-1 degree is common.
Probes are limited to your application. Some Kapton surface probe would be limited by the Kapton
What are you going to be measuring? Pipe clamp?
Readouts have another problem. I've had some that would start measuring at 250 degrees Centigrade. Not likely for your type of device.
Quick meter test. Short the inputs with a piece of copper wire, If the device is capable of measuring room temperature, it will read room temperature.
There is thermocouple wire and thermocouple extension wire. Don't confuse the two. You don't make junctions with extension wire.
Multiple parallel junctions average, Even when they are at the tip.
They are color coded. Yellow outer jacket is K. The inner conductors are colored too. RED is always negative for thermocouples in general, (at least in my experience). I've used R,S, J,K, T and C.
I'm familiar with mineature and full size connectors.
The junctions (or two 1/2 junctions) should be isothermal.
Old school was two thermocuples in series and one in an ice bath. Then use the tables (reference 0 C) to convert voltage to temperature.
New school. Use a precision semiconductor sensor an measure the temperature of the terminals. Do a reverse lookup and use that mV value. Add or subtract, then look value in a table or polynomial.
Thus the ability to ambient compensate is limited. The temperature where the meter is located.
I still have the actual K probe:
The probe, when plugged in, still shows temperatures but very inaccurately. You can see what happened in the third image with parts of the feed wire having insulation burned away. Perhaps it could be repaired? Never thought I could, just assumed I ruined it. The insulation looks like some form of Teflon or similar.
Thanks for the info. I just posted pictures of the probe and damage in my prior post. It does/did read room temperature. In fact, to my surprise, with the probe plugged in right now, it is measuring within 7 degree F of actual room temperature. With the missing sections of insulation, if I dip into any liquid, it throws the temperature way off.
I just stuck the probe under my tongue. In the past when it was working, it would read within +/-3 F of actual body temp, but today it drops to read nearly 0 F.
Such a 'probe' is just a pair of dissimilar wires, insulated on the length, welded at the tip. You can snip off the damaged bit, trim back the insulation, and re-weld a tip. Accuracy wont be harmed unless the alloy of the probes is significantly changed.
Solder or weld? I can do solder, but no welding capability here. Thanks, though.
Ok, I clipped off enough that, when I now touch the wires together, I get room temperature and body temp accuracy if I put the probe in my mouth. I can see the two wires under a magnifying glass. I wonder if I could use my "15 minute" oxygen/ propane torch to weld the tip?
You can probably cut the wires back to where the insulation is not melted and twist them together vrey tight and it will read the temperature at that point. If you could weld, not solder the wires together it should still work.
If you want to measure liquid temperture, the wires do have to be isolated from the liquid. Any thing that conducts electricity between the wires will cause a false reading.
It is probably showing the incorrect temperature in your mouth because the liquid or skin resistance is causing a false voltage between the wires without insulation.
They should be welded. Solder introduces another materal. The two wires are different materials all the way back to the meter. Even the plug should be made of the same material on each terminal. At the tip they are joined together and form a junction that generates a voltage depending on the temperature. I don't know if all metels do that or not, but do know there are about half a dozen types of T/Cs that are standard. Each one is designated a letter as to the material it is made of.
Where I worked we used thousands of them. Mostly J type and some K type. The company that made them for us was local and had a few spools of the wire reserved for us so they would be consistant. Even with that they could be off about 2 deg C at 300 deg C. from each other.
Part of my job was caliberating insturments that used them.
The insulation appears to be shredded near the thermocouple. As others have suggested, cut it back to where the insulation is still intact, and weld the tip. That's weld, NOT braze, solder, glue, crimp, sleeve, or twist. Just weld.
I only see one image and one URL, but it's enough. The insulation is gone. I'm not sure why you're getting "very inaccurate" readings. Are the readings high, low, erratic, intermittent, or insane?
Yes, by welding. However, it would be prodent to spend a few dollars and buy a new Type-K probe so that you can compare your repaired probe with one that is more likely to be accurate.
Nope. Note my domain name: LearnByDestroying.com. That means you don't really understand how something works until after you've broken it and subsequently repaired it.
The high temperature insulation can be PTFE (Teflon), PFA (perfluoroalkoxy or Neoflon), XC, XS, XR, or XC4: Chemically resistant wire uses FEP (fluorinated ethylene propylene) insulation.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Interesting, so even the welded wires still have to be insulated then. As you say, the reason for the faulty readings I am getting. Unfortunately, I don't have anything decent other than shrink tube and leftover high temp RTV to coat them with, so I think it's time for a new probe.
I will point out that the group has been a big help in informing me how these work and my thanks.
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