Hi-temp indicators?
August 28, 2012 8:10 AM Subscribe
Is there anything which will give a visible indication when the temperature is between 180-195deg C? Indicator needs to be multiple use, so reversible operation. Also needs to be passive.
Strips would be ideal, but dont go hot enough.
The only thing I can find is sodium which goes red around this temperature. This is not a particularly practical solution though! Is there anything produced for ovens, or industrial processes which I'm missing?
There are cooking thermometers with a probe that you can have in the oven and the LCD readout outside the oven - does that work or is it not "passive" (since it uses battery power)?
posted by EndsOfInvention at 8:43 AM on August 28, 2012
posted by EndsOfInvention at 8:43 AM on August 28, 2012
Your limit on reusable is 120C. You can find non-reusable strips that meet that temperature range, but keeping good adhesion on those can be an issue. There are traditional liquid thermometers that go to that range, but it seems like that is out of the question? Not having any idea what your application is it is hard to make recommendations. Thermal paints and lacquers, while one time use, can be reapplied. Wax is also an option, but would have to be reapplied or tracked.
Of course, if you are willing to go with something active then thermocouples all the way...
posted by Feantari at 9:24 AM on August 28, 2012
Of course, if you are willing to go with something active then thermocouples all the way...
posted by Feantari at 9:24 AM on August 28, 2012
Welders use temperature indicator crayons for metal temperatures. You draw a line on the metal in question, and when it attains the desired temperature, its appearance changes. The crayons are calibrated in 3 to 5 degree increments.
It sounds like you want a solution that involves a obvious reversible phase change, making a sort of binary display. This is about the least available industrial solution that there is. You might consider something else. You haven't been very specific about what you're doing, and satan is in the specification, as they say :-)
There are any number of other simple technologies that come in specific temperature ranges that require some supporting circuitry. Some of the circuitry could be as simple as a small light bulb and a battery, and others might require signal processing (like a thermocouple mentioned above or a pyrometer) if you wanted a binary go/no-go display.
You might consider one of these:
* Bimetal Thermal Protector
* Probe Thermostat
* Thermal Cutoffs
* Bulb and Capillary Thermostat
* stationary infrared pyrometer
posted by the Real Dan at 10:01 AM on August 28, 2012 [1 favorite]
It sounds like you want a solution that involves a obvious reversible phase change, making a sort of binary display. This is about the least available industrial solution that there is. You might consider something else. You haven't been very specific about what you're doing, and satan is in the specification, as they say :-)
There are any number of other simple technologies that come in specific temperature ranges that require some supporting circuitry. Some of the circuitry could be as simple as a small light bulb and a battery, and others might require signal processing (like a thermocouple mentioned above or a pyrometer) if you wanted a binary go/no-go display.
You might consider one of these:
* Bimetal Thermal Protector
* Probe Thermostat
* Thermal Cutoffs
* Bulb and Capillary Thermostat
* stationary infrared pyrometer
posted by the Real Dan at 10:01 AM on August 28, 2012 [1 favorite]
I feel pretty silly posting such an obvious thing, but you don't mention it in your question.
An analog temperature gauge won't use a battery. The probe/sender can be mounted away from the gauge if that's an issue.
Some gauges have an adjustable red area, which makes it easier to see at a glance the temp is in a given range.
posted by yohko at 2:03 PM on August 28, 2012
An analog temperature gauge won't use a battery. The probe/sender can be mounted away from the gauge if that's an issue.
Some gauges have an adjustable red area, which makes it easier to see at a glance the temp is in a given range.
posted by yohko at 2:03 PM on August 28, 2012
Tin melts at ~232C, bismuth ~271C, but a 58-42% Bi-Sn alloy melts at ~138C.
So somewhere between 58-42% Bi-Sn and 100% Sn there will be alloys that melt at the temperatures you're talking about (and bismuth and tin happen to be fairly non-toxic).
You could turn such an alloy into an indicator by sealing some of it into a glass ampoule (with air space remaining) and then melting it and letting it solidify lying on its side.
In a liquid bath such an indicator ampoule would float on its side until the alloy melted, and then flip up to vertical at the indicator temperature.
In a gas it would do the same thing if you mounted it on a pivot at the initial center of mass.
This company sells low temp Bi-Sn alloys, but all the ones listed on the page melt at too low a temperature for you, though others might be available.
posted by jamjam at 2:33 PM on August 28, 2012
So somewhere between 58-42% Bi-Sn and 100% Sn there will be alloys that melt at the temperatures you're talking about (and bismuth and tin happen to be fairly non-toxic).
You could turn such an alloy into an indicator by sealing some of it into a glass ampoule (with air space remaining) and then melting it and letting it solidify lying on its side.
In a liquid bath such an indicator ampoule would float on its side until the alloy melted, and then flip up to vertical at the indicator temperature.
In a gas it would do the same thing if you mounted it on a pivot at the initial center of mass.
This company sells low temp Bi-Sn alloys, but all the ones listed on the page melt at too low a temperature for you, though others might be available.
posted by jamjam at 2:33 PM on August 28, 2012
Response by poster: Thanks for all the suggestions. There's some great info there for me to follow up.
Loving the idea of a 'flipping' indicator, but not practical here.
'Silly and obvious' is good for me!
By 'passive' I mean requiring no additional power so anything requiring batteries or mains power to be able to get a reading is out, even if the sensor itself is 'passive'.
Space is also an issue; traditional thermometers are too big. Ideally I'm looking for the equivalent of a 200deg LCD strip.
The application is pretty simple; I want to know when a small disc of metal is within the required temperature range. Frequent heating to the desired temperature is part of the function of the device, so repeated application of paint/crayons is not practical. Similarly: there are devices which use batteries to manage the heating but the intention of this device is to be self sustaining.
posted by BadMiker at 3:26 AM on August 29, 2012
Loving the idea of a 'flipping' indicator, but not practical here.
'Silly and obvious' is good for me!
By 'passive' I mean requiring no additional power so anything requiring batteries or mains power to be able to get a reading is out, even if the sensor itself is 'passive'.
Space is also an issue; traditional thermometers are too big. Ideally I'm looking for the equivalent of a 200deg LCD strip.
The application is pretty simple; I want to know when a small disc of metal is within the required temperature range. Frequent heating to the desired temperature is part of the function of the device, so repeated application of paint/crayons is not practical. Similarly: there are devices which use batteries to manage the heating but the intention of this device is to be self sustaining.
posted by BadMiker at 3:26 AM on August 29, 2012
« Older Air conditioned spaces at the MN State Fair | Help me get my dad's lovelife on track Newer »
This thread is closed to new comments.
Not sure what you mean by this. There are tons of devices that will measure temperature and emit a signal, visual and/or audible, when a particular temperature range is reached.
posted by valkyryn at 8:11 AM on August 28, 2012