Temperature Instrumentation for Research and Industry


Sensors - Platinum Resistance Thermometers

Customized PRT's - Built to Your Design

Platinum Resistance Thermometers

Platinum Resistance Thermometers operate on the principle that the electrical resistance of a metal conductor changes as a function of temperature. PRT's provide an accurate, stable and repeatable means of absolute temperature measurement. The accuracy of a PRT may be independent of the distances between the sensor and the instrument whether it be an indicator, recorder, controller, data logger or computer. Copper hook-up wire is generally used between the sensor and instrument.

Marlin PRT probes consist of a platinum resistance element that is encapsulated and circuited in a mineral insulated, metal sheath construction and terminated by means of bare wire, quick connectors or terminal heads. This construction provides a rugged probe that is moisture, pressure, shock and vibration resistant and also is bendable up to the element area.

General Selection Parameters

The conditions of measurement determine the type of PRT used. Temperature, atmosphere, protection, response, and service life should be considered. The following descriptions serve as a guide to selection.

The Platinum Resistance Element
Select the PRT element that will be capable of operating in your application range. The reference resistance (100 Ohms@0°C - typical) and temperature coefficient (Alpha of 0.00385 - typical) must match the instrumentation in your system.
Tolerance of the PRT Element
A range of limits of error elements are available (0.1% - typical). In general the better the tolerance the more expensive the thermometer.
Sheath Alloy
Select a sheath alloy that will withstand the temperature and possible corrosives of your application. A 316SS sheath is standard.
Probe Diameter
Use the probe diameter that will withstand the rigors of your application but with minimal affect on it. Because the element can be broken if the sheath is bent in the element area, it is recommended that a minimum of 0.187" diameter thermometer be used. Smaller diameters are available on request.
(Please consult the factory.)
Process Connections
In order to attach and/or seal the thermometer in your application you can use a fitting - braze, weld or solder it in place.
Terminal and/or Extension Type
For connection to instruments various terminations and extensions are available. Select the circuit that is required to match your instrumentation.

For more information regarding Platinum Resistance Thermometers
Please Consult your Marlin Catalog.