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Thermotech's 1/2 x 1/2 Spring Loaded Hex RTD
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An RTD is simply a resistor that changes resistance with a change in temperature. The change in resistance is very linear with the temperature change for certain elements. These elements are the materials that RTD's are made from.
COMMON RTD'S AND RTD CURVES
The most common element used for RTD's is platinum. The platinum coil is available in several resistance ( ohm ) values with 100 ohms being the most used value. The " 100 ohm " nomenclature was derived from the fact that the 100 ohm platinum coil has a resistance of exactly 100 ohms ( -/- the accuracy tolerance) when the temperature of the coil is at ice point ( 0 C or 32 F). Another specifying factor for RTD's is the "curve". The curve for 100 ohm platinum RTD elements most commonly used is the 0.385 curve also called the European curve.
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THERMOTECH USA offers a complete line of quality RTD assemblies available in standard, cut to fit, vibration resistant and high temperature configurations
Standard configurations have silver coated, Teflon covered leads which are epoxy sealed upon exit of the sheath. This results in a rugged, moisture resistant probe.
Cut To Fit ( Ct) configuration has lead wires passing through a hollow sheath to the actual RTD element. The resulting assembly can be shortened to any length down to 2-1/2" minimum by carefully cutting off the section of hollow sheath, adjusting the wire length to suit and resealing the sheath.
Vibration Resistant (VR) version ( a Thermotech USA special) is offered for a more rugged RTD than the standard version.
High Temperature RTD for service from 450F up to 1100F in single and dual configurations. Thermotech’s high temperature units are available in a special bendable version that can be bent with tubing benders. The standard HT version is not bendable. (VR not available on "H" units).
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The standard accuracy of Thermotech USA RTD's is 0.1% ( band 1). Other bands up to Band 5, which is 0.01% tolerance. The accuracy of an RTD is generally better that thermocouples. Accuracy on RTD's is stated as the deviation from what is the standard resistance for an RTD at a certain temperature.
WIRES TYPES & NUMBER OF WIRES TO USE
RTDs can be either 2, 3 or 4 wires and in single or dual form. Our standard wire is a Teflon covered silver plated copper conductor in 20 gauge. This is a high quality conductor with the Teflon covering suitable for wire temperature up to 450 F.
Note: Thermotech's special high temperature construction allows the RTD to measure temperatures to 1000F and are bendable. Standard high temperature (1000 F limit ) construction, however, is not bendable.
RTD's in 2,3 or 4 wire forms all measure the temperature in the exact same way. The difference in the number of wires is to compensate for possible lead wire length errors caused by a difference in lead wire resistance. Since the RTD is basically a change in resistance and if the lead in wires have a difference in resistance, there is a possibility and a probability of an error in the temperature measurement due to the lead wires. A 2 wire RTD does not have the capability of reducing this error. Therefore a 2 wire should only be used with short leads wires and if accuracy is not a significant factor. The 3 wire configuration is most commonly used and has the ability to compensate for the lead wire error. A 4 wire has the capability to compensate the error, if any, on both of the lead wires. 4 wire is best to use when most concerned with accuracy of the temperature reading.
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SHEATH OUTSIDE DIAMETERS (O.D.)
RTD’s are available in tube OD’s from 1/8" up with the most common size being 1/4" .
RTD SHEATH MATERIAL
316 SS is Thermotech USA’s Standard material, any other commercially available weldable tubing can be used
SHEATH LENGTH
When used with a 1/2 x 1/2 hex fitting, the length can start at 0". We can make an RTD to any length specified.
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SHEATH MATERIAL LIMITS
Continuous Maximum Temperature Ratings F, in oxidizing atmospheres
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HEAD
ASSEMBLIES
Any of the following Thermotech USA standard thermal
heads can be used with the RTDs
From left to right:
Large cast iron weather proof
thermal head;
Standard cast aluminum weatherproof thermal head;
Standard cast iron weather proof thermal head;
Deldrin head weatherproof , corrosion resistant plastic
Polypro head weatherproof, corrosion resistant plastic
Cast aluminum or cast iron explosion proof head, these heads have
a 6 terminal barrier strip inside.
Email: sales@thermotechusa.com
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