Sensors

Therm-x manufactures a variety of Temperature sensors for critical process control. Thermocouples, RTD and Thermistor probes for specialized applications are designed and manufactured in our factory near Silicon Valley. High voltage isolation, Multi-point, Custom flanges, Unique bending configurations, Vacuum leak testing, Calibration to N.I.S.T

Vacuum feed-through thermocouples

• CF, KF and custom flanged thermocouples for Vacuum
• Helium Leak certified

Mineral insulated and tube and wire bent to custom configuration

• Multi point
• Custom bends to tight tolerance
• Twisted Shielded Hi-Isolation

Fast response R.T.D.

• Hyper Thermally conductive Tip
• 1.5 X Faster than standard RTD
• .125 - .188 O.D.
• Class A Din 385 Curve

Sensor types available

Mineral Insulated Thermocouples Mineral Insulated (MI) thermocouples consist of matched thermocouple wires surrounded by insulating material (typically magnesia oxide) compacted by drawing or swaging the sheath. The result is a rugged and reliable construction suitable for a wide variety of applications including Semiconductor wafer processing, heat treating, medical, nuclear reactors, refineries and oil processing, vacuum furnaces, laboratory and research, etc. Advantages of mineral insulated thermocouples are:

• Useable under severe conditions
• Withstands temperatures up to metal melting point
• Withstands corrosive conditions limited only by the choice of sheath material
• Can be formed to a minimum radius of twice the sheath diameter without loss of integrity
• Can be welded, brazed or soldered to other metals when proper techniques are used
• Available in a wide variety of diameters from .010” to .500”
• Available in standard and special limits of error
• Can withstand external pressures up to 50,000 psi
• Multiple element cable is available
  

M.I. cable specifications

Sheath Diameter: ± .002” or ± 1% of nominal diameter, whichever is greater.
Wall Thickness: ± .0015” or ± 15% of nominal wall thickness, whichever is greater, 10% of diameter as a minimum.
Insulation Material: 98% (min.) MGO Magnesium Oxide
Insulation Temperature: Insulation is useable over a temperature range of -450°F to 3000°F without change of phase or chemical
reaction with adjacent metals. Melting temperature of insulation is 4800°F. Limiting temperature is associated with sheath material used.

Soft Wire-Tube and wire thermocouple

In order to keep the two thermocouple wires apart from each thus causing a false junction, Wire is insulated with different types of insulation designed to work well with the particular application. PVC, Teflon, Polyamide, fiberglass and ceramic are the most common types of insulation used in thermocouples.

PVC, or Polyvinyl Chloride is typically used in lower temperature applications and also as extension or hookup wire to connect instruments together. Since its melting point is 221 degrees F, it cannot be used in high temperature applications. Teflon is the most common insulation used to make thermocouples. It is rated up to 550 degrees F° and has excellent chemical and abrasion resistive properties. Fiberglass is used in higher temperature applications and is rated up to 1000 degrees F°. It does not resist chemicals and is not good for abrasion. Wires can be braided with stainless steel and other insulation to make them more durable. Soft wire thermocouples can be crimped or potted in protection tubes made of ceramic or stainless as well as other sheath materials. Ceramics are used for bare wire and Nobel metal thermocouples.

RTD resistance temperature detector

This sensor has a more limited temperature range. Typically 600C is max, but due to epoxies and wire typically used, 500°F is standard.This is also a more accurate sensor than a thermocouple. RTDs come in different packages. The most common are thin film and Ceramic wire wound. Therm-x has thin film in a variety of sizes and tolerances. Wire wounds elements are available in special tolerances referred to as Bands 1-5. These are for application where the customer is looking for a product with higher accuracy than the industry standard.

Industry standards are defined by Curve, Resistance value and Class. The standard that we offer is the DIN 385 curve with 100 ohm resistance and Class B. There are other less common curves available. These curves refer to the resistance values read at different temperatures. These are defined in Temperature to resistance tables. The Class is typically either class A or B. This refers to the accuracy of the RTD. The resistance value is the resistance that the sensor reads at 0°C.

Thermistors are also a resistance temperature detector. They typically have a much higher resistance value such as 10K ohm at 25°C. Thermistors are also unusual in that they typically have a negative temperature coefficient. While RTDs resistance increases as the temperature rises, thermistors resistance decreases as the temperature rises. Thermistors are semiconductors and are known for their accuracy and repeatability. They are not typically used in industrial temperature applications because they are not very stable at high temperatures over 150°C.