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Pt100 - Platinum resistance temperature sensors

PT100 elements come in many types conforming to different standards, capable of different temperature ranges, with various sizes and accuracies available. But they all function in the same manner: each has a pre-specified resistance value at a known temperature which changes in a predictable fashion. In this way, by measuring the resistance of the element, the temperature of the sensor can be determined from tables, calculations or instrumentation. These resistance elements are the heart of the Pt100

Typical RTD pt100 element design: sensing core, coiled resitance element and the wires Resistance Temperature Detectors (RTD), as the name implies, are sensors used to measure temperature by correlating the resistance of the Pt100 sensor with temperature. Most RTD sensors consist of a length of fine coiled wire wrapped around a ceramic or glass core. The element is usually quite fragile, so it is often placed inside a sheathed probe to protect it.

The RTD sensor is made from a pure material whose resistance at various temperatures has been documented. The material has a predictable change in resistance as the temperature changes; it is this predictable change that is used to determine temperature.

  • Pt100 resistance value change with temperature

  • The IEC standard is 100 ohms at 0°C (Pt100)

  • Pt100's may be used from -270°CC to 850°CC

  • Click here to see some examples

They are all types of RTD (Resistance Temperature Detector) sensor that are made from Platinum. The Pt100 sensor has a resistance of 100 ohms at 0°C and is by far the most common type of RTD sensor. The Pt500 sensor has a resistance of 500 ohms at 0°C and the Pt1000 has 1000 ohms resistance at 0°C.

These sensors are normally fitted into some type of protective sheath or mounting to form a probe, and these are commonly referred to as PRT (Platinum Resistance Thermometer) or Pt100 probes.

Glass Wire Wound Platinum RTD Elements. The typical sensor There are two main types of Pt100 element: wire wound and thin-film.

Wire Wound Pt100 Elements

Wire wound elements consist of a length of fine Platinum wire coiled around a ceramic or glass core. These types of Pt100 sensor are typically 1 to 5mm diameter and 10 to 50mm in length. The ceramic or glass core can make them fragile and susceptible to vibration so they are normally protected inside a probe sheath for practical use.
The broadly used thin Film RTD Pt100 sensor

Thin Film Pt100 sensors

Thin film Pt100 sensors are manufactured using materials and processes similar to those employed in the manufacture of integrated circuits. A platinum film is deposited onto a ceramic substrate which is then encapsulated. This method allows for the production of small, fast response, accurate sensors.

The International Standard IEC 751:1983 specifies the tolerances for industrial platinum resistance thermometer sensors. There are two main tolerances defined for Pt100 probes: Class A, with a tolerance of ± 0.150°C at 0°C and Class B, with a tolerance of ± 0.3°C at 0°C. There are 2 additional accuracy classes for precision work and these are commonly referred to as "1/10 DIN" and "1/3 DIN" this means a tolerance of 1/10 or 1/3 of the Class B specification at 0°C respectively. The full Class A, B, 1/10 and 1/3 tolerances are listed in our Pt100 Accuracy Table along with details of the 2 main temperature coefficient curves available for Pt100 sensors.

Pt100 temperature probe with a RTD element inside the SS protection tube
The Pt100 is one of the most accurate temperature sensors. Not only does it provide good accuracy, it also provides excellent stability and repeatability. Most OMEGA standard Pt100 comply with DIN-IEC Class A.

Pt100s are also relatively immune to electrical noise and therefore well suited for temperature measurement in industrial environments, especially around motors, generators and other high voltage equipment.

RTD An acronym for resistance temperature detector or device. A resistance temperature detector

RTD Element Sensing portion of the RTD which can be made most commonly of platinum, nickel, or copper. OMEGA features two styles of sensors: wire wound and thin film.

Pt100 Probe An assembly composed of an element, a sheath, a lead wire, and a termination or connection. The standard OMEGA Pt100 probe is made with a 100 ohm platinum European curve sensor (alpha = 0.00385).

Platinum RTD Also known as Pt RTD, Platinum RTD's are typically the most linear, stable, repeatable, and accurate of all RTD's. Platinum wire was chosen by OMEGA because it best meets the needs of precision thermometry.

Thin Film RTD Thinfilm RTD's are made up of of a thin layer of a base metal embedded into a ceramic substrate and trimmed to produce the desired resistance value.

Class A RTD Highest RTD Element tolerance and accuracy, Class A (IEC-751), Alpha = 0.00385

Class B RTD Most Common RTD Element tolerance and accuracy, Class B (IEC-751), Alpha = 0.00385

Aplha .00385 Curve European Curve meets "0.1% DIN" standard tolerance and conforms to the DIN 43760 standard

Wire Wound The standard RTD sensors used in OMEGA's probe assemblies are made of 99.99% pure platinum wire wound about a ceramic or glass core and hermetically sealed within a ceramic or glass capsule.

 Types of RTD
1PT100G Pt100 glass with wire elements Pt100 Elements
The Pt100 element is the simplest form of RTD. It consists of a piece of wire wrapped around a ceramic or glass core. Because of their compact size, Pt100 elements are commonly used when space is very limited.

The most popular Pt100 elements. It can be easly manufactured in probes.

Pt100 Surface sensors
A surface sensor is a special type of Pt100 element. It is designed to be as thin as possible thus providing good contact for temperature measurement of flat surfaces.
PR-10 Pt100 industrial Probe. This kind of probes are broadly used in industrial applications

Pt100 Probes
The Pt100 probe is the most rugged form of RTD. A probe consists of an Pt100 sensor mounted inside a metal tube, also known as a sheath. The sheath protects the sensor from the environment. OMEGA offers a wide variety of probes in various configurations.

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