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Measurement technology

Thin film tip design

ifm uses a highly engineered construction method. The RTD element is first bonded to a thin film carrier. This reduces the thermal mass of the electrical leads. The film carrier and RTD element is then attached to a specialized assembly carrier. The carrier positions the RTD element into precisely the correct location and preloads the RTD with constant force against the probe’s inner sheath wall. This allows the RTD element direct and constant controlled contact to the sheath, minimizing the amount of thermal mass separating the RTD element from the process media. The result – fast and repeatable response!

Ordinary RTDs and temperature instruments have the sensing element potted into the tip of the sheath tube. The potting compound acts like an insulator, slowing the heat transfer to the RTD element. Typically, the RTD element location is not controlled, but simply lowered by its lead wires into the sheath and glued into place. Both of these factors lead to poor uniformity, repeatability and response time.

ifm instruments using the thin film tip design include the TN, TR, TA, TK, TV, TT and TM families.

Metallic bonded tip

This ifm design uses a revolutionary process that metallically bonds the RTD element directly onto the copper-plated inner wall of the probe tip. This creates very low thermal mass with a direct metallic bond for optimal heat transfer. The metallic bond technology eliminates all polymer parts allowing the sensor to be used at higher temperatures. Additionally the tip construction offers response speeds twice as fast as our already fast thin film design.

The image below shows the difference in response time from the thin film construction to the metallic bonded construction.

The metallic bonded construction is great for:

  • UHT (Ultra High Temperature) pasteurization processes
  • HTST (High Temperature Short Time) pasteurization processes
  • SIP (Steam-in-Place) measurement
  • Continuous processes where fast reaction speed and critical temperature measurement is required

ifm’s TA2 family of instruments for Food and Beverage / Sanitary applications use the metallic bonded tip construction.

Self verifying dual-element tip

The design of the TCC family of instruments includes two sensing elements that self-detect and send a warning if any signal drift is occurring. The PTC (Positive Temperature Coefficient) element increases its resistance with increasing temperature. The NTC (Negative Temperature Coefficient) element decreases its resistance with increasing temperature.

Because the PTC and NTC react to temperature change in opposite directions, the microprocessor is able to measures the differential between the two elements and alert the user to a potential decrease in accuracy.

Infared non-contact technology

Infrared temperature instruments, sometimes called pyrometers, detect the amount of infrared (IR) radiation emitted from the object. A lens focuses the infrared radiation onto a detector, which converts the energy into an electronic signal. This technology enables temperature measurement from a distance without requiring contact to the object.

All objects with a temperature above -273 °C (0 K) radiate some level of infrared energy. The object’s ability to emit this energy is known as emissivity (ε). Many factors influence the emissivity of the object including material and surface finish. A polished metal has a much lower emissivity than the same metal with a rough surface, for example. Emissivity information is available from internet searches, textbooks, etc., but the values in practice can vary due to target surroundings, shape and other factors. This table shows some examples:

Εmissivitiy ε

Material [%] Material [%]
Black body 100 Glass 85...95
Graphite 98 Iron oxide 85...89
Skin, human   98 Enamel 84...88 
Baking oven 96 Plaster   80...90
Bitumen (roofing cardboard) 96 Wood 80...90
Water 92...98 Textiles 75...88
Asphalt 90...98 Radiator 80...85
Table stove 95 Copper, oxidised 78
Marble 94 Chamotte 75
Rubber, black 94 Alumina 76
Brick 93...96 Leather 75...80
Soil 92...96 Clinker brick, glazed 75
Paints and lacquers, matt 96 Paper 70...94
Paints and lacquers, shiny 92 Steel, red oxidised 69
Lime plaster 91 Plastics, opaque 65...95
Sand 90 Concrete   55...65
Cement 90 Brass, oxidised 56...64
Bread in the oven 88 Steel, antirust 45

IR pyrometers are great for:

  • Detection of the presence of very hot objects (up to 4500 °F)
  • Temperature measurement of similar objects (emissivity factor required for accurate measurement)
  • Industries such as asphalt manufacturing, steel mills, glass plants, etc.

ifm offers infrared temperature sensors in our TW series.