need to find a replacement K type probe for this thermometer

[Jeff Liebermann]

On Thu, 31 Oct 2019 13:47:36 -0400, Jim Horton <jhorton@nospam.net>
wrote:

On 10/31/19 11:59 AM, Jeff Liebermann wrote:


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.
https://www.google.com/search?q=k-type+thermocouple+probes&tbm=isch
https://www.ebay.com/sch/i.html?_nkw=type-K+thermocouple+probe


I still have the actual K probe:

https://imgur.com/a/4H9rNrs

The probe, when plugged in, still shows temperatures but very
inaccurately.

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.

You can see what happened in the third image with parts
of the feed wire having insulation burned away.

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?

>Perhaps it could be repaired?

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.

>Never thought I could, just assumed I ruined it.

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 insulation looks like some form of Teflon or similar.

The high temperature insulation can be PTFE (Teflon), PFA
(perfluoroalkoxy or Neoflon), XC, XS, XR, or XC4:
<https://www.omega.com/en-us/wire-and-cable/thermocouple-and-rtd-wire-and-cable/xc-xs-xt-xl-wire/p/XC-J-20-50>
<https://assets.omega.com/pdf/cable-and-wire/thermocouple-and-rtd-wire-and-cable/XC_XS_XT_XL_WIRE.pdf>
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

 

[Jim Horton]

On 10/31/19 6:05 PM, Ralph Mowery wrote:

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.

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.

 

[Phil Allison]

Jim Horton wrote:

-------------------------------

I still have the actual K probe:

https://imgur.com/a/4H9rNrs

** Does that look like a "probe" to you ?

Replacements cost about $5

WTF are you doing here ?

Wasting our time for your fun ?

The probe, when plugged in, still shows temperatures but very
inaccurately.

** Yeah, the insulation has failed and there are shorts in the cable.

Did you try to measure a flame ?


..... Phil

 

[Jim Horton]

On 11/1/19 6:46 PM, Phil Allison wrote:

Jim Horton wrote:

-------------------------------
I still have the actual K probe:

https://imgur.com/a/4H9rNrs


** Does that look like a "probe" to you ?

Replacements cost about $5

WTF are you doing here ?

Wasting our time for your fun ?

No. Thermocouple. I stand corrected. The thermocouple isn't an
absolute necessity at the current time, but I miss having it working
correctly. It has been needing replacing for a couple of years and I
could have used it to measure wax temperatures recently. Instead I used
a cheap, wireless IR thermometer.

The probe, when plugged in, still shows temperatures but very
inaccurately.


** Yeah, the insulation has failed and there are shorts in the cable.

Did you try to measure a flame ?

To be honest, I don't remember. Either a flame or I was experimenting
with solar cookers using fresnel lenses a few years back. These can
become quite hot with large lenses like I had (3000+ F), so chances are
concentrated solar energy hit the insulation and melted it. Not sure,
however.

.... Phil