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High temp thermometer.

Discussion in 'Electronic Design' started by Ken S. Tucker, May 28, 2012.

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  1. 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,

    Looks pretty simple, hence...what am I missing?
  2. 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.
  3. 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...

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

    Jamie Guest

    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.

  6. 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).
    Stolen _from_ Edison?

    Best regards,
    Spehro Pefhany

  7. 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: email:

    Please visit my GURU's LAIR web site at
  8. Jamie

    Jamie Guest

    Yes, that is what I meant.
    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.
    Yes, that is correct. We have a separate control circuit just for that
    area, which handles both aspects.
    Sure.. Read your history.

    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.

  9. My thought also.

  10. Syd Rumpo

    Syd Rumpo Guest

    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.

    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.

  11. Uwe Hercksen

    Uwe Hercksen Guest


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

  12. 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,

  13. 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.
  14. dynamics (at)

    business address is

    OT:Just got a new organizer, so I have room for more good stuff,
    In application, the 'thermometer/thermocouple' goes to a triac
    controlled existing 'hot plate' heater.
  15. An "ambition" is to remove methanol from ethanol, but I think
    a common diode series will do for that, otherwise quite true.
  16. A still?

    Best regards,
    Spehro Pefhany
  17. 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
  18. 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
  19. Jamie

    Jamie Guest

    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"

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