Testing at High Temperatures

You are looking for a type B Thermocouple. it has a high range of over 3000 degrees Fahrenheit. If you are putting this in a medium you will want to get a thermocouple with some sort of ceramic coating on it to resist deterioration. I'm not familiar with Labview, but you can get a controller that will read the temperature and give out a 4-20mA signal, or pretty much any other signal that you need. Be advised, type B Thermocouples are expensive. We use type S Thermocouples in our application which has less rhodium than the type B and our thermocouple assemblies cost about 1200 USD.

Ya, Type B thermocouples are hugely expensive, (Pt 6% Rh vs Pt 30% Rh), and at 3000F at the very top of the range, not going to last very long.

Better bet is an optical sensor.

http://www.raytek.com/Raytek/en-r0/ProductsAndAccessories/InfraredPointSensors/ThermalertSeries/Default.htm

That would work depending on what he's measuring. If he is measuring air temperature that would be pretty close to useless. Would be helpful if he told us what type of medium he is trying to measure.

Good points.

A type R thermocouple may be a bit cheaper and will handle 3000F, I think we used Inconel metal sheath to protect the thermie from the process. Then a digital indicator or controller or even just a "thermocouple to mA converter" to give a handleable signal for Labview.

Rok

Thank you for your suggestions. At this point I can only use K type thermocouples because of the system that we are using is a omega's cold junction compensationer and only K type thermocouples are compatiable. I am how ever measuring air temperature. I ve looked further into options to detect this drastic change in temperature and thought that a breakwire would melt at this point giving a signal to Labview of loss of continuity. This project is evenually going to be desgined to with stand the 3000 degrees but for now if I can caputure the moment this furnance has fire in it then my circuit would have done its job. If theres any details or other information any one needs just let me know. Again thank you

If you are looking for fire, that's a horse of a different color. Get an ultraviolet flame sensor. Honeywell pretty much has a lock on the market for them. Just do a search for Purple Peeper. You get a controller to go with it, and this will have a relay that it can turn on when you have flame. If you aren't using it for a round the clock operation you would probably be best served by their mini peepers.

Very good idea. A mini-peeper, with a 7800 series controller, would do the trick. However, it should be pointed out that this setup will not read temperature, only indicate the presence of flame.

The mini-peeper is priced under $100, the 7800 series, with UV amp, is about $700.

www.honeywell.com

I am looking at the purple peeper now I hope it won't be a problem getting it ordered by the middle of september. Have any of you used it before, and if so what is the response time like?

I have about 300 of these Honeywell controllers throughout the shop. They are used for flame safety and management. Their response to a flame signal is immediate.

There are many configurations of this product, so you should contact Honeywell sales to be sure you order the right units for your application.

In the US: 1-800-343-0228

You can look at the many configurations here:

https://estore.industrialcontrolsonline.com/default.aspx?page=category%20search%20results&CatList=0&parent=2&tree=2*Boiler+Burner+Controls*0@@

Not sure if you are in the US or not. If you are, and the (I'm assuming here) furnace is over 150,000 BTU you are required to have a flame safety device on it. Refer to NFPA 86.

Also, I don't use mini peepers, I use the full version, the only real difference is that the full peeper has a shutter on it that verifies that the sensor is not saturated. If you use a mini peeper you would have to remove flame from the furnace I believe once every 24 hours to verify that the peeper is still working. Our Honeywell controllers have a 4 second timer on them, if it doesn't see flame for 4 seconds it will trip the safety latch valves.

"If you use a mini peeper you would have to remove flame from the furnace I believe once every 24 hours to verify that the peeper is still working."

I have many of the mini-peepers, you don't ever have to remove the flame. I have furnaces that literally run for 6 mo. at a time, between Christmas and summer shutdowns. A very real difference is the full version costs 20 times more:

https://estore.industrialcontrolsonline.com/default.aspx?page=item%20detail&itemcode=C7012E1112

Due to tighter regulations these days, all new instillations require the full version.

Thank you gentle men for your immediate responses you have truly helped me out and yes I am in the USA.

A "laser thermometer", being a non-contact measuring method, would seem to be a good direction to head towards.