fast response thermistor

  • Thread starter Christian Holzapfel
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Christian Holzapfel

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Hi NG,

for a surface measurement application I need a thermistor (NTC) with a
fast response time of max. 200ms in liquids. Where can I buy such
things, any recommendations?

Thanks!
~Christian
 
On Wed, 3 Dec 2008 03:39:35 -0800 (PST), the renowned Christian
Holzapfel <holzapfel84@web.de> wrote:

Hi NG,

for a surface measurement application I need a thermistor (NTC) with a
fast response time of max. 200ms in liquids. Where can I buy such
things, any recommendations?

Thanks!
~Christian
Thermistors are generally poorly suited for surface temperature
measurement applications.

Here's one that claims to meet your stated requirements:
http://www.betatherm.com/datasheets/datasheet.php?p_id=90

(although the obvious errors on the page lead one to wonder if it
really does..)


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
Christian Holzapfel <holzapfel84@web.de> wrote in news:c2f14345-a890-4978-
ade1-de4252e0d24a@13g2000yql.googlegroups.com:

Hi NG,

for a surface measurement application I need a thermistor (NTC) with a
fast response time of max. 200ms in liquids. Where can I buy such
things, any recommendations?

Thanks!
~Christian
Maybe a small Pt100 sensor, the bare unencapsulated kind? You'd need to put
come kind of coating to seal the wires but the rest is already sealed with a
high temperature glaze, and the response speed and low cost of the smallest
types might make them ideal.
 
Lostgallifreyan schrieb:
Maybe a small Pt100 sensor, the bare unencapsulated kind? You'd need to put
come kind of coating to seal the wires but the rest is already sealed with a
high temperature glaze, and the response speed and low cost of the smallest
types might make them ideal.
Do you have any links, company names e.g. to such small and fast
sensors? A Pt100 would be suitable as well, but all of them I found on
the internet while googlin' seem to be slower than the NTCs available.

In addition to the fast response time (<166ms), the sensor needs to be
galvanically insulated, since I have to measure the temperature of a
bare DIE mosfet's source surface (I know, strange shit). I plan to apply
the sensor (thermistor or pt100) with a thermal conducting glue to the
surface, so maybe these glues are insulating, but I'm not sure about that.

~Christian
 
"Christian Holzapfel".

In addition to the fast response time (<166ms), the sensor needs to be
galvanically insulated, since I have to measure the temperature of a bare
DIE mosfet's source surface (I know, strange shit).

** For god's sake man, forget thermistors or any other contact sensor -
use a bloody IR thermometer.

You do know what that is ?



...... Phil
 
Christian Holzapfel <holzapfel84@web.de> wrote in
news:gh6vp1$ssr$1@inlux3.rz.uni-kiel.de:

Lostgallifreyan schrieb:
Maybe a small Pt100 sensor, the bare unencapsulated kind? You'd need to
put come kind of coating to seal the wires but the rest is already
sealed with a high temperature glaze, and the response speed and low
cost of the smallest types might make them ideal.

Do you have any links, company names e.g. to such small and fast
sensors? A Pt100 would be suitable as well, but all of them I found on
the internet while googlin' seem to be slower than the NTCs available.
Nope, I looked at RS, but theyr range shrunk, it seems. Thing was about 5 mm
long, 2 mm wide, and it should be fast as it was thin and built on a
thermally conductive ceramic. All moot though, if you also need strong
electrical isolation try what Phil said, sense radiation not conduction. It's
cheap enough, by the look of some initial Google results.

In addition to the fast response time (<166ms), the sensor needs to be
galvanically insulated, since I have to measure the temperature of a
bare DIE mosfet's source surface (I know, strange shit). I plan to apply
the sensor (thermistor or pt100) with a thermal conducting glue to the
surface, so maybe these glues are insulating, but I'm not sure about
that.

~Christian
 
Spehro Pefhany schrieb:
Here's one that claims to meet your stated requirements:
http://www.betatherm.com/datasheets/datasheet.php?p_id=90
Sphero,
thanks for your reply. I already found betatherm.com by myself, but
unfortunately they did not reply to any of my requests.
Since I live in Germany and this is of semi-private interest, callin'
the US would be too much.
They have a nice NTC with a TC of 30 (!) ms in liquids, which would be
ideal. Maybe I can find a local distributor...

~Christian
 
Phil Allison schrieb:
** For god's sake man, forget thermistors or any other contact sensor -
use a bloody IR thermometer.

You do know what that is ?
I do know. But I need to feed the measurement results to a PC for
real-time analysis, so a IR thermometer with USB or RS232 interface is
needed. And these are waaaay to expensive, even those that do not match
my requirements in speed.
If you can show me a product that is fast enough and can be connected to
a PC running LabView, please please show me.

~Christian
 
"Christian Holzapfel"
Phil Allison schrieb:

** For god's sake man, forget thermistors or any other contact sensor -
use a bloody IR thermometer.

You do know what that is ?

I do know. But I need to feed the measurement results to a PC for
real-time analysis, so a IR thermometer with USB or RS232 interface is
needed. And these are waaaay to expensive, even those that do not match my
requirements in speed.
If you can show me a product that is fast enough and can be connected to a
PC running LabView, please please show me.

** I suggest you alter your unrealistic expectations to match reality.

Cos the other way around does not work too well.



..... Phil
 
In article <gh6vp1$ssr$1@inlux3.rz.uni-kiel.de>, Christian Holzapfel <holzapfel84@web.de> wrote:
Lostgallifreyan schrieb:
Maybe a small Pt100 sensor, the bare unencapsulated kind? You'd need to put
come kind of coating to seal the wires but the rest is already sealed with a

high temperature glaze, and the response speed and low cost of the smallest
types might make them ideal.

Do you have any links, company names e.g. to such small and fast
sensors? A Pt100 would be suitable as well, but all of them I found on
the internet while googlin' seem to be slower than the NTCs available.

In addition to the fast response time (<166ms), the sensor needs to be
galvanically insulated, since I have to measure the temperature of a
bare DIE mosfet's source surface (I know, strange shit). I plan to apply
the sensor (thermistor or pt100) with a thermal conducting glue to the
surface, so maybe these glues are insulating, but I'm not sure about that.
So the sensor is going to be permanately attach with glue ? No liquids ?
Most are insulating. The trouble is spacing. I have used diamond dust
to help out as a spacer, You can apply a thin epoxy coat first, before
the final attachment, but I don't know the response.

greg
 
Christian Holzapfel wrote:
Lostgallifreyan schrieb:
Maybe a small Pt100 sensor, the bare unencapsulated kind? You'd need
to put come kind of coating to seal the wires but the rest is already
sealed with a high temperature glaze, and the response speed and low
cost of the smallest types might make them ideal.

Do you have any links, company names e.g. to such small and fast
sensors? A Pt100 would be suitable as well, but all of them I found on
the internet while googlin' seem to be slower than the NTCs available.

In addition to the fast response time (<166ms), the sensor needs to be
galvanically insulated, since I have to measure the temperature of a
bare DIE mosfet's source surface (I know, strange shit). I plan to apply
the sensor (thermistor or pt100) with a thermal conducting glue to the
surface, so maybe these glues are insulating, but I'm not sure about that.
If all else fails consider AC excitation and transformer coupling. Or
run the whole circuit isolated (that's what we do on ECG systems).

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
 

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