PT100 Sensor Guide for Accurate Industrial Temperature Measurement
Introduction
Temperature is one of the most commonly monitored process variables in industrial environments. From manufacturing machinery and chemical processing equipment to motors, generators and heating systems, knowing the temperature at a particular point can be important for process monitoring and equipment operation. The PT100 RTD is a widely used technology for this purpose.
Unlike a thermocouple, which produces a small voltage related to temperature, an RTD measures temperature through a change in electrical resistance. A PT100 uses platinum and has a nominal resistance of 100 ohms at 0 degrees Celsius. Raystek Process Instruments provides PT100 and other RTD configurations for industrial temperature measurement and customization.
Understanding how the sensor works can make it easier to choose an appropriate configuration.
The Basic Operating Principle
A PT100 works because the electrical resistance of platinum changes as its temperature changes. Measurement instrumentation supplies an electrical signal to the sensor and determines the resistance. That resistance can then be associated with a temperature value.
The 100-Ohm Reference
The "100" in PT100 refers to the nominal 100-ohm resistance at 0 degrees Celsius.
Raystek's technical information identifies PT100 as a platinum RTD with a nominal resistance of 100 ohms at 0 degrees Celsius and a commonly used temperature coefficient of 0.00385.
The relationship between resistance and temperature is the basis of PT100 temperature measurement.
Why RTDs Are Used in Industry
Industrial users often need repeatable temperature measurement. An RTD provides a standardized sensing method that can be integrated with indicators, controllers, transmitters and other instrumentation.
Raystek offers temperature indicators and controllers that support PT100 sensor inputs.
Measurement and Control
A PT100 sensor can provide an input to a temperature controller. The controller can compare the measured temperature with a configured setpoint and, depending on its control design, operate an output.
This makes the sensor an important part of a larger temperature measurement and control system.
PT100 Versus Different Wiring Methods
One of the most important technical decisions is the wiring configuration.
Raystek provides 2-wire, 3-wire and 4-wire PT100 configurations.
How Lead Resistance Matters
Connecting wires have their own resistance. With a two-wire arrangement, the measurement system can include the resistance of the wires in its reading.
A three-wire arrangement is commonly used in industrial systems because it can compensate for lead resistance under suitable conditions.
Four-wire configurations can provide a more direct measurement arrangement and are useful where higher accuracy is required.
Accuracy Classes
The accuracy class defines the allowable tolerance associated with the RTD.
Raystek lists DIN Class A and Class B options. Its technical data gives a Class A tolerance of plus or minus 0.15 degrees Celsius and a Class B tolerance of plus or minus 0.30 degrees Celsius at 0 degrees Celsius.
Choosing the Appropriate Class
Higher nominal accuracy can be useful when a process requires tighter measurement control. However, sensor accuracy is only one part of the complete measurement chain.
Installation conditions, wiring, instrumentation, calibration and process placement can also influence the practical measurement.
Temperature Range
The sensor must be selected for the required operating range.
Raystek's RTD specifications list configurations covering ranges from approximately minus 200 degrees Celsius to 400 degrees Celsius and, for applicable configurations, up to 600 degrees Celsius.
Why Range Should Be Confirmed
A sensor should not be selected simply because it is called PT100. The actual element construction, insulation, sheath, cable and mounting arrangement must be suitable for the expected process conditions.
The maximum temperature of the complete assembly may also depend on components other than the sensing element.
Mechanical Construction
The environment around the sensor can be just as important as the electrical characteristics.
Raystek lists multiple sheath diameters and SS316 as a standard sheath material, with alternative materials available on request.
Probe Diameter and Insertion Length
Probe dimensions should correspond to the available installation space and measurement point.
A probe that is too short may not reach the desired measurement location, while a probe that is unnecessarily long may create installation complications.
The diameter can influence mechanical strength, response characteristics and compatibility with fittings or thermowells.
Process Connections
Industrial PT100 sensors can be mounted using different connections.
Raystek lists BSP and NPT connections, compression fittings, PT100 Sensor Manufacturer adjustable flanges, Tri-Clamp connections, nipple arrangements and other options.
Matching the Connection to the Equipment
The connection PT100 Sensor Manufacturer should be selected according to the existing process interface. Food and pharmaceutical installations may have different requirements from general industrial piping.
A mismatch between sensor connection and process equipment can result in installation problems, so this specification should be confirmed before ordering.
Applications Across Industry
PT100 sensors are used in diverse applications.
Raystek identifies chemical, pharmaceutical, food, dairy, plastic, packaging, textile, power, steel, metal, cement, glass and petrochemical industries among RTD applications.
Motors and Generators
Raystek provides bearing temperature detectors using RTD or thermocouple elements and stator winding RTDs for large motors and generators.
These applications demonstrate how RTD technology can be adapted to specific mechanical constraints.
Installation Planning Checklist
Before specifying a PT100, an engineering team can gather:
Required temperature range
Desired accuracy
Wiring configuration
Probe diameter
Insertion length
Process connection
Sheath material
Cable length
Enclosure requirements
Thermowell requirements
Quantity
Instrument input specification
This information can make communication between the buyer, sensor manufacturer and instrumentation team more precise.
Conclusion
PT100 sensors work by measuring the predictable change in platinum resistance as temperature changes. Their standardized characteristics make them useful for industrial measurement and control systems.
The selection process should consider electrical configuration, accuracy, operating range, mechanical dimensions, process connection and environmental protection rather than focusing only on the PT100 designation.
Raystek Process Instruments offers PT100, PT200, PT500, PT1000 and other RTD configurations and provides customization based on application requirements.
A properly specified PT100 sensor can be integrated into industrial instrumentation to provide dependable temperature measurement. The correct configuration ultimately depends on the process conditions, equipment design and measurement objectives.