How to order RTD's

[windpomp]

First of all: I know that I don't know much.

I'm trying to get prices for RTD's, but the supplier only tells me that the information I give them is "sketchy". This guy is not very helpful in letting me know what he needs to be able to give me a price.

So I'm asking you guys: what information do I need to give the supplier for him to give me an accurate quote?

 

[JLSeagull]

Several resistance temperature detector types exist. Within the same type there are different curves and accuracy specifications. The most common within my field in the U.S. hydrocarbon process industry is called 100 ohm platinum with the alpha of 0.00385.

The RTD assembly likely includes a single wire wound element of 99.99% pure platinum wire, on a ceramic or glass core at the end of a tubing sheath filled with magnesium oxide insulation and a hermetically transition to extension wire within some type protective cable. This may be a one meter armored cable terminated in a weatherproof termination head.

Back the the process end the length of the sheath is normally associated with a thermowell that is installed via a flange or threaded connection to the process piping.

Different choices exist for every paragraph above.

 

[JLSeagull]

The term alpha applies to the temperature curve coefficient in unites of ohms per ohm per degree C. Besides 0.00385, the next most common coefficient is likely 0.00392 for laboratories.

For a complete assembly I specify the thermowell flange connection size such as NPS 1.5 Class 300 RF type 316 stailles steel and the well insertion length such as 6-inches and bore of 0.260-inch. This sets the RTD length and diameter. I also specify something like one meter of armored cable and a cast aluminum termination assembly. We often have some criteria for a specific plant. Another common arrangement includes nipples and a union to connect the RTD with the termination enclosure.

This background compared with your requirements then a couple of hours poking around on the web should make it easier to speak with the peddler.

 

[JJPellin]

A typical stock item for an RTD we use includes all of the following:

RTD,MINIATURE,100 OHM,PLATINUM,6 WIRE,CASE STYLE "C",DUAL JUNCTION,120" LEAD,TEFLON COATED,0.00385 TEMPERATURE COEFFICIENT,MINCO P/N;S14455PD3T120.

As a minimum, you need to specify the style, number of junctions, lead length, sheathing or coating, temperature coefficient and number of wires.

Johnny Pellin

 

[rmw]

You need to know the classification for the area where you intend to mount it. If you are a manufacturer, you may want to get a dual classified model so that it can ship anywhere worldwide.

You will need to know if you need a thermowell with it (or not).

You will also need to know if you want a single channel or a dual channel model.

What size pipe it is going on (or insertion depth of where ever it is going-you can see what I do with them)

rmw