Pt100 - Frequently Asked Questions (FAQ)
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A Pt100 is an electrical temperature sensor that uses the electrical resistance of platinum to measure temperatures. At 0 °C, its resistance is exactly 100 ohms, hence the name: “Pt” stands for platinum and “100” for the resistance at 0 °C. Pt100 sensors are characterized by high accuracy and stability and are often used in industry. More info
A Pt1000 is a temperature sensor that uses the electrical resistance of platinum to measure temperature. At 0 °C, its resistance is exactly 1000 ohms. The name is made up of the chemical symbol for platinum (“Pt”) and the resistance value at 0 °C (“1000”). Pt1000 sensors are known for their high accuracy and stability and are used in many industrial applications.
Both are resistance thermometers that use the resistance of platinum to measure temperature. The main difference lies in the nominal resistance at 0 °C: the Pt100 has 100 ohms, while the Pt1000 has a higher resistance of 1000 ohms. Due to the higher resistance, the Pt1000 offers a better resolution when measuring temperature changes. More info
The Swiss physicist Willy Jentzsch developed the first Pt100 sensor in 1927. More info
When measuring temperature with Pt100 sensors, a change in the electrical resistance of the connecting cable is included in the measurement. Depending on the length of the connecting cable and the required accuracy, a 2-, 3- or 4-wire connection is used. We recommend at least a 3-wire connection. More info
The resistance of the connection cable can be calculated using the formula R= ρ x L / A.
R= Resistance of the cable [ohms]
ρ= Specific resistance of the cable [ohms x mm² /m]
L= Total length of the cable (i.e., forward and return cable) [m]
A= Diameter of the cable wire [mm²]
More info
A change in temperature at the connection cable of the Pt100 leads to a change in resistance and thus to measurement errors. To avoid this effect, a 3-wire connection is used. More info
A Pt100 is often connected via a connection cable that is several meters long. Temperature changes on the cable are included in the measurement and distort the measurement result. With a 2-wire connection, this is noticeable in the measurement with approx. 0.4 °C per meter of cable. For the most accurate measurements, a 4-wire connection with an additional measuring circuit to compensate for the cable resistance should therefore be used. A compromise between cost/benefit is the 3-wire connection, in which the line resistance is determined with a 3rd cable. More info
There are various connection heads for connecting a Pt100 resistance thermometer, which are often also suitable for holding a head transmitter. The cover is hinged, fastened with a thread or 2 screws. The standard material is cast aluminum, plastic for simple applications or stainless steel for hygienic environments. Some variants are defined in DIN (form A, form B etc.). More info
A standard copper cable can be used to connect a Pt100 sensor. More info
The following cable colors are recommended in DIN EN 60751. Red and white for 1 sensor. When using two Pt100 sensors, the additional colors yellow and black or grey are used for the second sensor. More info
Most Pt100 sensors have an accuracy class in accordance with the DIN EN 60751 standard. In countries outside Europe, other standards are also used (e.g., ASTM E 1137), which specify different accuracies or accuracy classes. Example: Class B according to DIN: deviation of 0.3°C at 0°C. More info
The self-heating of a Pt100 sensor is caused by the measuring current that flows through the sensor and generates a power loss. Factors such as the level of the temperature measurement resistance, the dissipation of heat through the measurement medium, the measurement current itself and the thermal conduction of the measurement fitting influence the level of self-heating. More info
Conduction errors in Pt100 sensors can be minimized by using 3- or 4-wire technology. This compensates for the resistance of the connecting cables, which can lead to measurement errors with 2-wire connections, especially with long or thin cables. More info
The response time of a Pt100 sensor depends on the design of the temperature sensor (e.g. use of thermal paste, tapered measuring tip), the measuring medium (thermal conductivity and flow rate) and the installation depth and position of the sensor in the medium. The response time is defined in standards such as DIN 60751 by T50, T63 and T90 values. More info
The most important standard for Pt100 sensors is DIN EN IEC 60751:2023-06, which defines the calculation formulas, accuracy classes, measuring current, connection types, etc. More info
With a PTC resistor, the resistance value increases as the temperature rises. It has a higher conductivity at low temperatures and is therefore also called a PTC thermistor. The Pt100 is therefore a PTC.
A Pt100 temperature sensor has a resistance of 100 ohms at 0°C. The resistance at other temperatures can be calculated using the formulas specified in DIN EN 60751. More info
The resistance of Pt100 sensors is calculated according to 2 formulas defined in DIN EN 60751. The formula to be used depends on the temperature to be measured (< 0 °C oder > 0 °C). More info