You dont need a Type K thermocouple until you get in the 100s of
degrees... like for exhaust temperature but a max6675 thermocouple
preamp lets you read 0-1023 deg c on an SPI interface. An IC like an
LM35 puts out 10mv per degree C, has 3 wires, read with an a/d input.
A maxim DS18B20 reads 16th degrees C on a 2 wire digital bus. There
are Positive Temperature Coefficient and Negative TC thermistors that
are accurate but nonlinear and need the correct bias resistor to
prevent self heating. Read with a/d input. Phew. Lots of choices.

You dont need a Type K thermocouple until you get in the 100s of
degrees...

Forget I said K-Type Thermoprobe

What is the type of probe that is in that picture, measuring the
temperature of that hard drive?

I would like to get a temperature probe like this, from an electronics
place.

How would it be described technically?  I know they have specific
names, for the form of the bit at the end.  K-Type e.t.c.

Here is a picture (it is measuring a HDD temp)http://www.overclockersclub.com/reviews/nzxt_sentry/images/12.htm

I am also interested in the same question, regarding this probe.
It is measuring CPU temphttp://www.overclockersclub.com/reviews/nzxt_sentry/images/9.htm

Note- I know there are other ways. Software, IR Temp sensor Gun, to
measure temp of components. But I am interested particularly, in these
temp probes like in the picture.  some wires and a thing on the end,
and you tape it to the component and read the temperature.

Thanks.

"jameshanle... at (no spam) yahoo.co.uk" wrote:
They said I can't just attach a thermocouple to a DMM, because I won't
get an accurate reading.. They won't have "Fault Junction
Compensation".   He said Thermocouple (or K-Type?) sockets are more
common than Thermistor..

He said 'cold junction' actually. I don't know how they get round that but trust me
they do work.

However those cheap DMMs with K-type inputs actually perform very well.
I 'calibrate' them with boiling water before
use and it's rare to see one even as bad as 2C out.

Forget thermistors totally.

"jameshanle... at (no spam) yahoo.co.uk" wrote:
Eeyore wrote:
Phil Allison wrote:
"BobG"

You dont need a Type K thermocouple until you get in the 100s of
degrees...

** Not true.

K-type thermocouples are ideal for many applications over a very wide temp
range  -  mainly due to the tiny thermal mass and size of the bead that has
to be heated (or cooled).

Perfect for small semiconductors, heatsinks and inaccessible spots.

In any case, most K probes are sold with Teflon coated lead wires and so are
only safe up to 250 C max.

I agree 100%.

Furthermore, there are many quite inexpensive DMMs with K-type inputs. A K-type
thermocouple is the simplest to use for the non-expert who doesn't want to get
involved in all the fuss with different themocouple materials.

One small point. K-type connectors used to be colour coded yellow. It seems to
have changed to green now for some daft reason. They are compatible though.

Graham-

Can you name some places selling them? I will check if any ship to
britain..

Farnell has them.http://uk.farnell.com/jsp/search/browse.jsp?N=500005+1002025+106132&N...
some 100+

The simple bare junction type at the top of the list should do you find.

I will look into John Larkin's suggestion too, of cheap DVMs with K-
Type inputs.

They're all over the place. Funnily enough often on some of the cheaper Asian meters.
I've found these to be quite satisfactory.

According to this site
http://www.picotech.com/applications/thermocouple.html

K-Type refers to the metal the thermocouple (or perhaps, the
thermistor) ,

It does. The TWO metals in fact.

is made from. Not the plug.

The plug is colour coded to match the thermocouple, so as to avoid accidentally
mixing up incorrect thermocouples.http://uk.farnell.com/jsp/search/browse.jsp;jsessionid=VK5NRESE3QUL4C...

I see Farnell still stock the yellow type.

Is there a chance that a K-Type Thermocouple from one place will not
plug into a Multimeter from another place?

Not if it's the 'standard' plug.

I know for example that probes from one multimeter tend not to fit
into another one.

Not if they're 4mm types which all decent meters have.

Graham-

I see, K-Type refers to the power end, not the sensing end , which was
what I was wondering about.

I will get a DMM with a K-Type socket .. And a K-Type thermistor to
match.

Regarding material for the thermocouple. My friend did mention that a
thermocouple uses 2 different metals, to get a difference in voltage.
But a)I will be using a thermistor anyway b)I just ask the electronics
store for one that goes 0-100C , and a table. That's the
functionality, so the implemenetation - if there are differences ,
makes no difference to me.

If for example I don't get a K-Type plug DMM and K-Type Thermistor.
Are there then any issues with wrapping wire around the legs of a bead
thermistor, tying them to it with insulation tape, and connecting them
to a DMM with crocodile clips?

Thanks

Eeyore wrote:
Phil Allison wrote:
"BobG"

You dont need a Type K thermocouple until you get in the 100s of
degrees...

** Not true.

K-type thermocouples are ideal for many applications over a very wide temp
range - mainly due to the tiny thermal mass and size of the bead that has
to be heated (or cooled).

Perfect for small semiconductors, heatsinks and inaccessible spots.

In any case, most K probes are sold with Teflon coated lead wires and so are
only safe up to 250 C max.

I agree 100%.

Furthermore, there are many quite inexpensive DMMs with K-type inputs. A K-type
thermocouple is the simplest to use for the non-expert who doesn't want to get
involved in all the fuss with different themocouple materials.

One small point. K-type connectors used to be colour coded yellow. It seems to
have changed to green now for some daft reason. They are compatible though.

Graham-

Can you name some places selling them? I will check if any ship to
britain..

I will look into John Larkin's suggestion too, of cheap DVMs with K-
Type inputs.

According to this site
http://www.picotech.com/applications/thermocouple.html

K-Type refers to the metal the thermocouple (or perhaps, the
thermistor) ,

is made from. Not the plug.

Is there a chance that a K-Type Thermocouple from one place will not
plug into a Multimeter from another place?

I know for example that probes from one multimeter tend not to fit
into another one.

They said I can't just attach a thermocouple to a DMM, because I won't
get an accurate reading.. They won't have "Fault Junction
Compensation". He said Thermocouple (or K-Type?) sockets are more
common than Thermistor..

I see, K-Type refers to the power end, not the sensing end , which was
what I was wondering about.

I will get a DMM with a K-Type socket .. And a K-Type thermistor to
match.

Regarding material for the thermocouple.

On Wed, 21 May 2008 18:53:06 -0700 (PDT), "jameshanle... at (no spam) yahoo.co.uk"





jameshanle... at (no spam) yahoo.co.uk> wrote:
I would like to get a temperature probe like this, from anelectronics
place.

How would it be described technically?  I know they have specific
names, for the form of the bit at the end.  K-Type e.t.c.

Here is a picture (it is measuring a HDD temp)
http://www.overclockersclub.com/reviews/nzxt_sentry/images/12.htm

I am also interested in the same question, regarding this probe.
It is measuring CPU temp
http://www.overclockersclub.com/reviews/nzxt_sentry/images/9.htm

Note- I know there are other ways. Software, IR Temp sensor Gun, to
measure temp of components. But I am interested particularly, in these
temp probes like in the picture.  some wires and a thing on the end,
and you tape it to the component and read the temperature.

Thanks.

The simplest for a one-off application such as this is an ordinary
diode junction whose forward "resistance" is measured with an ordinary
DMM on Ohms range.  The Ohms range drives a constant current through
the diode, and the diode's forward voltage drop falls with increasing
temperature.  This is *very* linear, better than almost anything else
you will find (vastly better than thermocouples or thermistors).  Not
to mention being dirt cheap, and available in fairly small packages.

The only drawback is that each unit must be calibrated individually,
which is why you don't see this used more often.  (It *is* commonly
used to sense CPU and other chip temperatures for fan activation,
where precise temperatures are not really needed.)

Calibration consists of inserting the diode into an ice bath,
then a boiling water bath, and noting the readings on the DMM.
Any intermediate temperature is found via simple interpolation.
You can also extrapolate outside this range.  The basic concept is
good from near absolute zero until the junction starts to melt.

Note that you may need to coat the diode leads with something to keep
the water from them during calibration.

Bob Masta