DS2760 and Omega Pipe Plug Probe?

Bill Chennault

All--

I am thinking about building a microcontroller operated model boiler for a model steam engine driven electrical generating plant. It would be a great project combining three of my hobbies; robotics, machining, and steam engines. To do it the way I want, I need to measure the water/steam temperature in a few places; boiler, boiler fire tube, and boiler exhaust.

I am wondering if the DS2760 can be interfaced to an Omega "Pipe Plug Probe" Type T·(TC-T-1/8NPT-G-72)? I think I need the grounded version of the Type T probe. The DS2760 kit specs on the Parallax site mention the inclusion of a Type T thermocouple. I would experiment with the kit's Type T thermocouple and then use the Omega part which I can screw into the side of my boiler. It will also handle the exhaust temperature. I will have to experiment a bit to determine if it will handle the fire tube temperature but I am fairly confident it will as long as I don't put it too close to the flame. I was thinking of placing it after the first two Galloway tubes. (Galloway tubes are merely water tubes that criss-cross in the fire tube. If I place the thermocouple behind the first set, they will be positioned to measure the temperature I really would like to measure, which is far lower than the actual flame temperature.)

I don't have a clue! If you do, I would love to hear it!

Thanks!

--Bill

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
You are what you write.

kf4ixm

i dont see any reason why you couldn't use it, though with type t thermocouple, it only has a temperature range of -200 to 350c, while type k has a range of -200 to 1350c range. if it was me, id use type k on the fire tube temp, type t on the rest. just my 2 cents worth though. P.S. you can buy a 100' roll of type k thermocouple wire from grainger for about $90, and make your own thermocouples from now till the cows come home. all you have to do is braise the leads on one end together,(this would be the sensing end)·and there you go! Also you can buy the thermowells separate, if you want the ntp threaded insert, just make the thermocouple as above, insert down the center of the thermowell without the junction·touching the sides or bottom, fill with a fine grain sand 3/4 to the top, then fill the rest with epoxy. thats how most off the shelf thermocouples are made.

Post Edited (kf4ixm) : 1/15/2010 6:05:16 PM GMT

Bill Chennault

kf4ixm--

Wow! Great info! Thanks a ton!

I'll proceed with some confidence, now.

--Bill

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
You are what you write.

kf4ixm

no problem! glad to be of help! be sure to checkout the wikipedia page for thermocouples, it has a chart on there that shows the different color code associated with each type and the polarity of each wire, which sometimes isnt what you think it'd be, like type j·have a red and white wire, (ansi color coding)·the white is actually the positive lead and red is negative. if in doubt, just use a meter on dc on the leads, if it's a negative voltage, then reverse the leads.·it also breifly explains cold junction, which is very important for accurate reading, but i believe the kit parallax sells has that, so shouldnt be a concern.

Post Edited (kf4ixm) : 1/15/2010 6:36:10 PM GMT

Bill Chennault

kf4ixm--

Thanks for the link.

After reading that article, I know almost enough to be dangerous.

--Bill

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
You are what you write.

kf4ixm

Also i would try to use an ungrounded thermocouple setup. Although the internal thermocouple conductors are welded together they are electrically insulated from the external sheath material and are not connected to the sheath or thermowell·in any way. Ungrounded junction thermocouples are ideal for use in conductive solutions or wherever circuit isolation is required. Ungrounded junctions are required where the measuring instrumentation does not provide channel to channel isolation. this would minimize the chance of·any transient voltage spikes in the equipment being measured·from popping the ds2760 or damaging other sensitive electronics, like the stamp or propeller.·