High temp thermometer.

[Ken S. Tucker]

Need a high temperature thermometer, 500-600F is the ok
for now. I figure to use a tungsten (W), bulb and measure
its resistance....see link table 1 on how W ohms varies/K,

http://hypertextbook.com/facts/2004/DeannaStewart.shtml

Looks pretty simple, hence...what am I missing?
Ken

 

[Spehro Pefhany]

Response time might be an issue. Smash the bulb.

Low wattage 120V bulbs are apparently mostly vacuum inside-- higher
wattage ones have some inert gas.

Why not use a thermocouple? Or an RTD? That temperature is in the
'friendly' range.

 

[Ken S. Tucker]

Response time might be an issue. Smash the bulb.

It has the thermal inertia of a 'hot plate', in which it
will be in direct contact.
Speakin' of "smashing bulbs" I designed an easy ultra low
current igniter from one...

http://www.nakka-rocketry.net/igniter.html#Ultra

Regards
Ken

 

[Ken S. Tucker]

What's wrong with a platinum resistance thermometer element?
http://en.wikipedia.org/wiki/Resistance_thermometer

Cost and performance. A bulb costs $.05 and is good to 2000F,
using steel wire connects and glass is ok near 2000F,
http://hypertextbook.com/facts/2002/SaiLee.shtml

600F is 315.6C. You can buy them off the shelf.
http://www.newark.com/labfacility/dm-508/sensor-pt100-thin-film-2x5mm-cl/dp/24M1444

Check $.
Regards
Ken

 

[Spehro Pefhany]

It has the thermal inertia of a 'hot plate', in which it
will be in direct contact.
Speakin' of "smashing bulbs" I designed an easy ultra low
current igniter from one...

http://www.nakka-rocketry.net/igniter.html#Ultra

Regards
Ken

You can also make a Pirani vacuum gauge with one, if you can expose
the filament to the chamber.

 

[Jamie]

You can also make a Pirani vacuum gauge with one, if you can expose
the filament to the chamber.

if you're talking about an iron gauge, that requires a rather good
vacuums before you energize the heater. I suppose one could make one.

Mr Edison discovered the thermionic effect, trying to do research on
the soot build up on the heaters in lamps. His work led to many new
ideas that got stolen by big business and other proclaimed inventors.

Jamie

 

[Spehro Pefhany]

if you're talking about an iron gauge, that requires a rather good
vacuums before you energize the heater. I suppose one could make one.

You mean an _ion_ gauge (eg. Bayard-Alpert)? No, those are kind of a
gassy triode.

A Pirani gauge measures the heat loss in keeping a filament at a fixed
temperature, which is more-or-less linear with pressure over a range.
Kind of like a hot-wire anemometer in still air.

Their useful range is mostly at higher pressures than the ion gauges
(before you dare fire up the filament in the ion gauge).

Mr Edison discovered the thermionic effect, trying to do research on
the soot build up on the heaters in lamps. His work led to many new
ideas that got stolen by big business and other proclaimed inventors.

Jamie

Stolen _from_ Edison?


Best regards,
Spehro Pefhany

 

[Don Lancaster]

Response time might be an issue. Smash the bulb.

And the problem with a thermocouple is...?


--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email: [email protected]

Please visit my GURU's LAIR web site at http://www.tinaja.com

 

[Jamie]

You mean an _ion_ gauge (eg. Bayard-Alpert)? No, those are kind of a
gassy triode.

Yes, that is what I meant.

A Pirani gauge measures the heat loss in keeping a filament at a fixed
temperature, which is more-or-less linear with pressure over a range.
Kind of like a hot-wire anemometer in still air.

We also have a thermocouple vacuum probes in our system, too. It just
heats an element and senses it, but the ion gauge is the final
determination before HV is enabled.

Their useful range is mostly at higher pressures than the ion gauges
(before you dare fire up the filament in the ion gauge).

Yes, that is correct. We have a separate control circuit just for that
area, which handles both aspects.

Stolen _from_ Edison?

Sure.. Read your history.
http://www.andycowley.com/valves/old/history/genesis.html

You read down a bit and see how the Edison effect gets a
new label on it and then becomes some one else's property.

Nice world we live in. Bunch of cut throats.

Jamie

 

[Martin Riddle]

Thermocouple? http://en.wikipedia.org/wiki/Thermocouple

Type J should do just fine and there are lots of cold junction
compensated
transducers available.

My thought also.

Cheers

 

[Syd Rumpo]

On 28/05/2012 21:59, Bill Sloman wrote:

Choose your glass carefully. 2000F is 1093C, and soda glass melts
around there

http://en.wikipedia.org/wiki/Soda-lime_glass

Yes, use a halogen bulb - they have a quartz envelope which will easily
take that. A G4 capsule type isn't too big.

I used these as combined heaters/thermistors in a recent project where
the duty cycle was such that they had plenty of time to reach ambient
after the heating phase. Worked fine, but I found silver braze to be
the most reliable way of connecting wires which were then insulated with
fibreglass. In my case, the temperatures were lower than yours, so I
don't know if silver braze or fibreglass would survive.

Copper braid is tempting as connecting wire, but be wary of the odd
broken strand poking though the fibreglass sleeving, so use single core
if you can.

Cheers

 

[Uwe Hercksen]

Today many bulbs or lamps are made of molybdenum. Because it is cheaper. So you should calibrate your sensor.

Hello,

the melting point of molybdenum is 2623 °C, but tungsten is 3422 °C.

Bye

 

[Ken S. Tucker]

On 28/05/2012 21:59, Bill Sloman wrote:



Yes, use a halogen bulb - they have a quartz envelope which will easily
take that. A G4 capsule type isn't too big.

I used these as combined heaters/thermistors in a recent project where
the duty cycle was such that they had plenty of time to reach ambient
after the heating phase. Worked fine, but I found silver braze to be
the most reliable way of connecting wires which were then insulated with
fibreglass. In my case, the temperatures were lower than yours, so I
don't know if silver braze or fibreglass would survive.

Nice post Syd.
I'm planning to crimp steel or Cu wire to bulb leads.
For insulation, I figured on Telfon or ceramic, but fiberglass sounds
like a nice suggestion.
Lot's of good posts to this thread fellas,
Thanks
Ken

 

[Spehro Pefhany]

A thermocouple starts to sound better and better. You can buy a cheap
DVM that has a thermocouple input.

OP: Send me your e-mail and I'll send you a type K bead thermocouple.

They're rugged, have fast response, are trouble-free and just what the
doctor ordered for this kind of application.

 

[Ken S. Tucker]

OP: Send me your e-mail and I'll send you a type K bead thermocouple.

dynamics (at) uniserve.com

business address is
http://www.trak4.com/earco/index.html

OT:Just got a new organizer, so I have room for more good stuff,

http://www.flickr.com/photos/dynamics/?saved=1

They're rugged, have fast response, are trouble-free and just what the
doctor ordered for this kind of application.

In application, the 'thermometer/thermocouple' goes to a triac
controlled existing 'hot plate' heater.
Regards
Ken

 

[Ken S. Tucker]

As Phil Hobbs says, even at a sweet spot, they are still
thermocouples, and consequently unsuited to making accurate
temperature measurements, not that Ken S. Tucker is going to be
ambitious about accuracy.
Bill Sloman, Nijmegen

An "ambition" is to remove methanol from ethanol, but I think
a common diode series will do for that, otherwise quite true.
Ken

 

[Spehro Pefhany]

dynamics (at) uniserve.com

business address is
http://www.trak4.com/earco/index.html
Done.


In application, the 'thermometer/thermocouple' goes to a triac
controlled existing 'hot plate' heater.
Regards
Ken

A still?


Best regards,
Spehro Pefhany

 

[Spehro Pefhany]

It's cheaper to buy pure ethanol in the first place.

Except for the taxes. According to C. this was a common activity among
the chemistry Uni students. Get it right and cheap booze, get it wrong
and you go blind!


Best regards,
Spehro Pefhany

 

[Spehro Pefhany]

An "ambition" is to remove methanol from ethanol, but I think
a common diode series will do for that, otherwise quite true.
Ken

BP of ethanol and methanol are 78.37°C/65°C so there's a reasonable
separation. AFAIUI, denaturing uses more than one additive so as to
make the process more difficult to reverse.


Best regards,
Spehro Pefhany

 

[Jamie]

Thermocouples are pretty good, usually better than their specs
suggest. They are much more rugged than RTDs, and work to much higher
temperatures.

The biggest practical problem is that most readout devices have
miserable cold-junction sensing for any CJ temperature but 20C. If you
do it right, it's remarkable how accurate thermocouples are.

Why do you reflexively add insults to most everything you post?

other issues with thermocouple process units is they need to operating
in the same ambient temperature as the device the probe is connected too.
The cold junction reference will miss calculate otherwise..The
seebeck effect is a basic thing, however, not very understood by a few,
especially those that carry a name of "SLow-Man"

Jamie