Steve,
Good question.
I found that if I used the plastic coated ones that sometimes if the
plastic sheathing of two wires touched at the wrong time during the
reflow profile one or more of the two touching wires would give screwy
readings - either go to zero or give a reading of 300+C, which of course
is ridiculous. On examination I would find that the plastic was actually
fused together.
I then switched over to the ones coated with the high temp "cloth" and
have eliminated the problem stated above. I have used these
thermocouples many, many times and have not seen an issue. I have three
to six thermocouples on the samples, so I have a pretty good idea of
what I should be getting. The agreement is usually less than +/- five
degrees for the sample type I was using.
Bev
RIM
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Tuesday, October 02, 2007 2:04 PM
To: [log in to unmask]
Subject: [TN] Thermocouple Longevity?
Hi Everyone!
How many reflow profiles do ya'll put the same thermocouples through
before you think about replacing them?
I've typically used them until they quit working or the insulation
deteriorates so bad that I don't want to use them anymore. I was told
that was not a good practice. That your typical K thermocouple starts
drifting after only 4 or 5 thermal cycles. I said; "Really?" I didn't
want to debate a whole lot because it was a customer who said this, so I
just agreed and went on.
So, do any of you know this to be a fact, and do any of you trash a
thermocouple after only 4 or 5 profiles and replace them with new ones?
Kind regards,
Steve Gregory
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