WHC228@AOL.COM on sat 19 jan 02
I need to add to the information that I just sent that I use S type
thermocouples. They last much longer than the K type at higher temperatures.
They are expensive, but worth it. I use them with a mullite protection tube.
I have some in my gas kilns that are fifteen years old and still are doing
their job.
Last year I ordered an electric kiln that had a K type thermocouple and the
first one failed on its 21st firing. I replaced them with S type couples and
have not had any trouble since. The problem with the K type couples is that
they go through changes before they fail completely.
You will notice a drift away from the reliability that you expect from your
controller.
The S type couple is more expensive, but worth it. It will probably cost less
than a load of pots that weren't fired properly.
It isn't what you pay for something, it is what it costs you. It is always a
lot more fun to work with good tools.
Bill Campbell
Stephen J Lewicki on mon 21 jan 02
Bill -
I would second what you say. Interestingly, even though we offer Type S
thermocouples as an option, you are the only customer we have had take us
up on it. Type S thermocouples are made of platinum for those out there who
don't know and they are very expensive. When you add three together for a
three zone control system it can add almost $500 to the cost of a kiln.
That is more than most (perhaps almost everyone) can afford although you
make a great point about cost rather than price.
We have been selling "industrial grade" Type K thermocouples for several
years and have found these to be pretty good. They are made from a material
called Hoskins 2300mi and probably have the best life of any Type K
thermocouple. Big problem though - Hoskins just went belly-up and didn't
bother to sell their proprietary material production to anyone. We are
exploring a number of alternatives and plan to run a controlled test with a
sophisticated datalogger and about 15 different combinations including Type
N sheathed and unsheathed, 8 gauge Type K in a protection tube, Pyrocil-C
Type K, and various other combinations. We are actually going to use a Type
S as our control thermocouple. It will be very interesting to see what
happens.
Stephen J Lewicki
President
L&L Kiln Mfg., Inc.
877-513-7869
steve@hotkilns.com
Fredrick Paget on tue 22 jan 02
All this posting about various thermocouples may lead someone to think that
they would be well off to substitute a different type for the type K that
came with their kiln.
Just to set the record straight the other couples put out a considerably
different electrical signal for any temperature they are exposed to than
the K. You have to have new firmware installed in the controller -generally
that means buying a new controller board that goes with the type S for
example.
Fred
From Fred Paget, Marin County, California, USA
Natalie Winter on tue 22 jan 02
In message <193.15403b7.297b1f99@aol.com>, WHC228@AOL.COM writes
>I need to add to the information that I just sent that I use S type
>thermocouples. They last much longer than the K type at higher temperatures.
Have you considered using Type N couples? They're a relatively new type
that combines the cheapness of Type K with the durability of the
platinum (types R/S) couples, but is more stable long-term than either.
They are good up to Cone 10 and much less prone to contamination than
the platinum couples. I use them exclusively, and with good results.
Most brands of instrumentation that can accept multiple different types
of t/couple can accept type N nowadays. Another big advantage of Type N
is that the "cold" end of the couple can be much hotter than that of
Type R/S without introducing errors -- anything over about 80C will
adversely affect the accuracy of Type R/S compensating cable, but Type N
uses matched rather than compensating extension cables and can tolerate
any temperature that won't cause physical damage, in practice about
200C.
Type N's are usually metal sheathed (nicrosil) so they are much more
robust than porcelain sheathed couples. They are suitable for reduction
or oxidation, and with an ITC coating will last almost indefinitely.
They are starting to be used more widely in industrial ceramics as
people become aware of their advantages. I pay about $20 (one-off) for
Type N couples, a little more than Type K but much, much less than
platinum couples!
Hope this helps
Nali.
Natalie Winter in Exeter, SW England
The Dawnmist Website: http://www.dawnmist.demon.co.uk
WHC228@AOL.COM on tue 22 jan 02
Steve
The price for the S type really is cheap when compared to the loss of just
one load of pots. The big problem as I see it is they really start to give
bad information before they fail completely. I'm sure that you have seen the
charts that are published to predict when they will begin to fail. I would be
far less concerned if I fired to a lower temperature, and in a less hostile
environment.
I ordered a kiln from another kiln company nearly two years ago, and
specified an S type couple. The delivery was being delayed because they
didn't have any S type couples, so I allowed them to ship the kiln with
sheathed K type couples. The first one failed within a six weeks. The others
were giving me bad information so the results were off. The problems cleared
up immediately when I changed to the S couple. I fire a lot. Usually every
third day, so those K couples probably only had 14 to 20 fireings before I
gave up. I keep pretty good records and know that I made the replacement on
the 21st fire.
The new kiln is working perfectly, Thank you
Bill
Bobbi Bassett on tue 22 jan 02
In a message dated 1/22/2002 8:59:01 AM Eastern Standard Time,
natalie@DAWNMIST.DEMON.CO.UK writes:
> Type N's are usually metal sheathed (nicrosil) so they are much more
> robust than porcelain sheathed couples. They are suitable for reduction
> or oxidation, and with an ITC coating will last almost indefinitely.
> They are starting to be used more widely in industrial ceramics as
> people become aware of their advantages. I pay about $20 (one-off) for
> Type N couples, a little more than Type K but much, much less than
> platinum couples!
>
Can these be used on a Scutt Controller? If so, where do you get them at that
price?
Bobbi in PA
Hank Murrow on tue 22 jan 02
>Bill -
>
>I would second what you say. Interestingly, even though we offer Type S
>thermocouples as an option, you are the only customer we have had take us
>up on it. Type S thermocouples are made of platinum for those out there who
>don't know and they are very expensive. When you add three together for a
>three zone control system it can add almost $500 to the cost of a kiln.
>That is more than most (perhaps almost everyone) can afford although you
>make a great point about cost rather than price.
>
>We have been selling "industrial grade" Type K thermocouples for several
>years and have found these to be pretty good. They are made from a material
>called Hoskins 2300mi and probably have the best life of any Type K
>thermocouple. Big problem though - Hoskins just went belly-up and didn't
>bother to sell their proprietary material production to anyone. We are
>exploring a number of alternatives and plan to run a controlled test with a
>sophisticated datalogger and about 15 different combinations including Type
>N sheathed and unsheathed, 8 gauge Type K in a protection tube, Pyrocil-C
>Type K, and various other combinations. We are actually going to use a Type
>S as our control thermocouple. It will be very interesting to see what
>happens.
>
Now this is a great response from a manufacturer! I hope there is a
special corner in heaven for folks like this. I look forward to hearing the
results of the testing program, and hope it appears on Clayart.
Regards, Hank in Eugene
WHC228@AOL.COM on tue 22 jan 02
Nali
Thank you for letting me know about the N type couples. I would have to
investigate to see if the are appropriate to my fireing. I fire to ^10 in a
zinc rich atmosphere. I am using them to fire zinc macro crystalline glazes.
I am also not sure if they can be adapted to be used by my controllers. I
don't know what the EMF difference is between those metals. I will however
check it out. The price is very attractive.
I probably will not change for a long time because I have S couples throught
my system, and some spares. Since they never have failed for me it may be a
long time before I need another
Bill
WHC228@AOL.COM on wed 23 jan 02
Fred
Most of the controllers that are currently being sold have the ability to be
changed by pushing a couple of buttons on the controller. It is very easy to
make that switch.
It is good that you pointed out that there is a difference in the output of
the couples and that the change needs to be made.
Bill
Natalie Winter on wed 23 jan 02
In message , Bobbi Bassett
writes
>Can these [type N thermocouples] be used on a Scutt Controller? If so,
where do you get them at that
>price?
You'll have to contact Skutt for that info, as I'm a Brit and we don't
get Skutt kit over here. But you can buy thermocouples from electronic
supply houses. My usual supplier is Farnell Components. They're on
1-800-718-1997 in the USA and the order codes are as follows according
to length:
150mm 707-9072
250mm 707-9084
Don't forget to use Type N connecting cable if you change your
thermocouples -- type S cable won't work with a type N couple!
Hope this helps,
Nali.
Natalie Winter in Exeter, SW England
The Dawnmist Website: http://www.dawnmist.demon.co.uk
Natalie Winter on wed 23 jan 02
In message <9c.19c3b53b.297f0281@aol.com>, WHC228@AOL.COM writes
>Nali
>Thank you for letting me know about the N type couples. I would have to
>investigate to see if the are appropriate to my fireing. I fire to ^10 in a
>zinc rich atmosphere. I am using them to fire zinc macro crystalline glazes.
They're definitely OK for that -- that's exactly what I use them for,
except that I only fire to cone 8. I'm a crystalline glaze freak, there
are examples on my website if you're interested. Cone 10 is right at the
top limit for Type N -- 1300 C. Coating with ITC is a really good idea
at the top temperatures.
The EMF/temp curve for Type N is very different to Type R/S. N's are
more sensitive, which makes for better accuracy as there are more
millivolts to play with, but you do need a controller that "knows" about
Type N. Mine is specifically designed for Type N, though it's adaptable
for other types.
Hope this helps
Nali.
Natalie Winter in Exeter, SW England
The Dawnmist Website: http://www.dawnmist.demon.co.uk
Stephen J Lewicki on wed 23 jan 02
To all -
Type N does in fact have a different EMF curve than Type K. On both the
DynaTrol (our control) and Skutt's control this is hard programmed into the
control. Our control supplier (Bartlett) does have the ability to program
the Type N curve in just as they can program the Type S curve in. A
philosophic decision was made by both Dave Bartlet and at least us (and
perhaps other of his customers) NOT to make this programmable. The
consequences of a customer misprogramming this WOULD be disastrous (i.e.
total kiln meltdown). So when we get an order for a Type S control we
special order it (which is quick). If we do end up changing over to Type N
based on our testing we will have to order different software with our
controls and, as was pointed out in the discussion, different lead wire.
I would like to have a retrofit kit available (again if we do this) but the
cost and trouble of doing that remain to be seen. We would at least
continue to carry the best of the Type K thermocouples for backwards
compatibility.
Stephen J Lewicki
President
L&L Kiln Mfg. Inc.
877-513-7868
steve@hotkilns.com
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